Potent inhibition of human phosphodiesterase-5 by icariin derivatives

Design, synthesis and evaluation of carbamate-bridged amino acid prodrugs of cycloicaritin with improved antitumor activity, aqueous solubility and phase II metabolic stability

Cycloicaritin (CICT), a bioactive flavonoid derived from the genus Epimedium, exhibits a variety of beneficial biological activities, including promising anticancer effects. However, its poor oral bioavailability is attributed to its extremely low aqueous solubility and rapid elimination via phase II conjugative metabolism. To overcome these limitations, we designed and synthesized a series of carbamate-bridged prodrugs, protecting the hydroxyl group at the 3-position of cycloicaritin by binding with the N-terminus of a natural amino acid. The optimal prodrug 4b demonstrated a significant increase in aqueous solubility as compared to CICT, as well as improved stability in phase II metabolism, while allowing for a rapid release of CICT in the blood upon gastrointestinal absorption. The prodrug 4b also facilitated oral absorption through organic anion-transporting polypeptide 2B1-mediated transport and exhibited moderate cytotoxicity. Importantly, the prodrug enhanced the oral bioavailability of CICT and displayed dose-dependent antitumor activity with superior safety. In summary, the prodrug 4b is a novel potential antitumor drug candidate, and the carbamate-bridged amino acid prodrug approach is a promising strategy for the oral delivery of CICT.

Comparing Western and traditional Chinese medicine for male sexual dysfunction: can Klotho represent a silk road?

Traditional Chinese medicine (TCM) and Western Medicine both have shown efficacy in treating male sexual dysfunction (MSD). The aim of this perspective paper is to discuss a possible link between Western medicine and TCM in the MSD field as represented by the entity of Klotho. Klotho is a recently discovered protein, mainly expressed in the kidney, encoded by the anti-aging gene klotho. Not only is Klotho significantly correlated with the development and progression of kidney diseases and their complications, but increasing evidence indicates that it is also closely related to MSD. A comprehensive search within PubMed database was performed to retrieve available evidence on Klotho's roles, particularly in kidney and in MSD. Indeed, in the TCM theory, the concept of the "kidney" is entirely different from the Western medicine: it is closely related to metabolism and to the reproductive, nervous, endocrine systems, being more than just a urinary organ. According to the "Kidney storing essence (jīng) and governing reproduction" (KSEGR) theory, a cornerstone in TCM, the treatment of MSD mainly consists of restoring the kidney's function. Signs of decreasing kidney essence show a consistent similarity to deficiencies of Klotho, also for what regards the male sexual function. Based on the current evidence, Klotho may represent a potential biological indicator for sexual desire and sexual function and a kind of new scientific Silk Road between TCM and Western medicine for MSD; nevertheless, there is a need to conduct further high-quality research to prove this hypothesis.

Composition Characterization of Cinnamomum osmophloeum Kanehira Hydrosol and Its Enhanced Effects on Erectile Function

Cinnamomum osmophloeum Kanehira (CO) is an endemic species of Taiwan. This study elucidated the composition of CO hydrosol, revealing trans-cinnamaldehyde (65.03%), trans-cinnamyl acetate (7.57%), and coumarin (4.31%) as the main volatile compounds. Seven compounds were identified in the water fraction of hydrosol, including a novel compound, 2-(2-hydroxyphenyl)oxetan-3-ol. This marks the first investigation into high-polarity compounds in hydrosol, extending beyond the volatile components. Notably, two compounds, trans-phenyloxetan-3-ol and cis-phenyloxetan-3-ol, demonstrated significant inhibition activity against phosphodiesterase type five (PDE5), with IC50 values of 4.37 µM and 3.40 µM, respectively, indicating their potential as novel PDE5 inhibitors. Furthermore, CO hydrosol was evaluated against enzymes associated with erectile dysfunction, namely acetylcholinesterase (AChE), angiotensin-I converting enzyme (ACE), and arginase type 2 (ARG2). These findings underscore the potential of CO hydrosol to modulate erectile function through diverse physiological pathways, hinting at its prospects for future development in a beverage or additive with enhanced effects on erectile function.

Establishment and optimization of a high-throughput UPLC-MS/MS method for the simultaneous quantitation of cycloicaritin and its valine carbamate prodrug in rat plasma

An ultra-performance liquid chromatography-tandem mass spectrometry was developed to assay the concentration for the quantification of cycloicaritin and its carbamate prodrug (3-O-L-valyl carbamate prodrug of cycloicaritin) in the plasma of Sprague-Dawley rats. Analytes were separated on an Acquity UPLC BEH C18 (2.1 × 50 mm, 1.7 μm) after liquid-liquid extraction with methyl tert-butyl ether. Acetonitrile and water containing 0.1 % formic acid were the mobile phases of the method. Using electrospray ionization in the positive ion mode, the method was performed with a total run time of 2.60 min. The response of the experiments was linear over the concentration ranges from 1 to 250 ng/mL for cycloicaritin and 1-250 ng/mL for prodrug. The intra- and inter-day precision and accuracy were within the recommended limits of the FDA. The matrix effect that we observed met the criteria. The method was successfully applied to the pharmacokinetics of cycloicaritin and its carbamate prodrug in Sprague-Dawley rats.

Production of Rhamnosyl Icariside II by snailase hydrolysis of Epimedium wushanense extracts

Rhamnosyl Icariside II is a rare secondary flavonoid glycoside isolated from Epimedium L. plants. It has better stability and physiological activity than the primary flavonoid glycosides of Epimedium L., therefore, conversion of the primary flavonoid glycoside into Rhamnosyl Icariside II would be desirable. In this study, a method for the enzymatic production of Rhamnosyl Icariside II from the total flavonoids of Epimedium wushanense was established, and the conditions were optimized. Six commercial enzymes were screened, and the reaction conditions for the best enzyme were optimized. Snailase was the most effective hydrolase, and the highest yield was obtained under the optimized conditions. To facilitate industrial production of Rhamnosyl Icariside II, a scaled-up pilot test was performed. The reaction solution was extracted with n-butanol to obtain the Rhamnosyl Icariside II crude product, which was then subjected to silica gel column chromatography and preparative chromatography. Finally, a product of Rhamnosyl Icariside II with purity of 99.1 % was achieved, in a total yield of 46.8 %. Compared to direct extraction and acid hydrolysis, this method improves the product yield and purity, which is of great significance for the large-scale production of Rhamnosyl Icariside II. This study provides a basis for the physiological activity study of Rhamnosyl Icariside II, and offers possibilities for future applications in the healthcare sector.

Herba Epimedii and Increased Opioid Cravings While on Buprenorphine: A Case Report

Herba Epimedii, commonly known as yin yang huo, inyokaku, and horny goat weed, is a traditional Chinese herbal medicine utilized for treating osteoporosis and enhancing libido. Studies conducted in vitro have demonstrated that Herba Epimedii interacts with the enzyme cytochrome P450 3A4 (CYP3A4). This interaction poses a potential risk for drug-drug interactions, particularly with medications metabolized by CYP3A4, such as buprenorphine. This paper presents a case of a patient experiencing exacerbated opioid cravings following the initiation of Herba Epimedii. This is the first reported case supporting this interaction, emphasizing the necessity of screening for alternative medicines in patients undergoing medication-assisted treatments for opioid use disorder.

Role of Nutraceuticals in Treating Erectile Dysfunction via Inhibition of Phosphodiesterase-5 Enzyme: A Mini Review

Erectile Dysfunction (ED) is a prevalent sexual health condition affecting a significant portion of the male population worldwide. The conventional therapeutic approaches for ED often involve the use of pharmaceutical agents targeting the phosphodiesterase-5 (PDE5) enzyme. Currently, treatment with PDE-5 inhibitors is the standard approach for ED, and four PDE-5 inhibitors, namely sildenafil, vardenafil, tadalafil, and avanafil, are in use. However, these pharmaceutical interventions may be associated with adverse effects and limitations. As a result, there has been a growing interest in exploring alternative and complementary treatment options for ED, such as nutraceuticals, which are bioactive compounds derived from natural sources. Nutraceuticals, which include vitamins, minerals, herbs, and other dietary supplements, have gained popularity for their potential health benefits. Certain nutraceuticals have demonstrated the ability to modulate various physiological pathways, including those involved in erectile function. A notable mechanism of action is the inhibition of the PDE5 enzyme, which plays a pivotal role in the regulation of cGMP levels. By inhibiting PDE5, nutraceuticals can promote the accumulation of cGMP, leading to enhanced penile blood flow and improved erectile function. A comprehensive analysis of the literature showcases various nutraceutical agents, including plant-derived compounds like flavonoids, polyphenols, and amino acids which have exhibited PDE5 inhibitory effects. Mechanistic insights into their action involve modulation of NO release, cGMP elevation, and relaxation of penile smooth muscles, all critical factors for achieving and sustaining erections. This review focuses on elucidating the role of nutraceuticals in treating erectile dysfunction through the inhibition of the PDE5 enzyme.

Effects of Icariin and Its Metabolites on GPCR Regulation and MK-801-Induced Schizophrenia-Like Behaviors in Mice

Icariin, a major bioactive compound found in the Epimedium genus, has been reported to exert protective effects against neurodegenerative disorders. In the current study, we aimed to investigate the regulatory effect of icariin and its active metabolites (icariside II and icaritin) against prime G-protein-coupled receptor targets, considering their association with neuronal disorders. Icariside II exhibited selective agonist activity towards the dopamine D3 receptor (D3R), with half-maximal effective concentrations of 13.29 μM. Additionally, they effectively inhibited the specific binding of radioligands to D3R. Molecular docking analysis revealed that icariside II potentially exerts its agonistic effect through hydrogen-bonding interaction with Asp110 of the D3R, accompanied by negative binding energy. Conversely, icaritin demonstrated selective antagonist effects on the muscarinic acetylcholine M2 receptor (M2R). Radioligand binding assay and molecular docking analysis identified icaritin as an orthosteric ligand for M2R. Furthermore, all three compounds, icariin and its two metabolites, successfully mitigated MK-801-induced schizophrenia-like symptoms, including deficits in prepulse inhibition and social interaction, in mice. In summary, these findings highlight the potential of icariin and its metabolites as promising lead structures for the discovery of new drugs targeting cognitive and neurodegenerative disorders.

Targeting beta-catenin signaling for prevention of colorectal cancer - Nutraceutical, drug, and dietary options

Progressive up-regulation of β-catenin signaling is very common in the transformation of colorectal epithelium to colorectal cancer (CRC). Practical measures for opposing such signaling hence have potential for preventing or slowing such transformation. cAMP/PKA activity in colon epithelium, as stimulated by COX-2-generated prostaglandins and β2-adrenergic signaling, boosts β-catenin activity, whereas cGMP/PKG signaling has the opposite effect. Bacterial generation of short-chain fatty acids (as supported by unrefined high-carbohydrate diets, berberine, and probiotics), dietary calcium, daily aspirin, antioxidants opposing cox-2 induction, and nicotine avoidance, can suppress cAMP production in colonic epithelium, whereas cGMP can be boosted via linaclotides, PDE5 inhibitors such as sildenafil or icariin, and likely high-dose biotin. Selective activation of estrogen receptor-β by soy isoflavones, support of adequate vitamin D receptor activity with UV exposure or supplemental vitamin D, and inhibition of CK2 activity with flavanols such as quercetin, can also oppose β-catenin signaling in colorectal epithelium. Secondary bile acids, the colonic production of which can be diminished by low-fat diets and berberine, can up-regulate β-catenin activity by down-regulating farnesoid X receptor expression. Stimulation of PI3K/Akt via insulin, IGF-I, TLR4, and EGFR receptors boosts β-catenin levels via inhibition of glycogen synthase-3β; plant-based diets can down-regulate insulin and IGF-I levels, exercise training and leanness can keep insulin low, anthocyanins and their key metabolite ferulic acid have potential for opposing TLR4 signaling, and silibinin is a direct antagonist for EGFR. Partially hydrolyzed phytate can oppose growth factor-mediated down-regulation of β-catenin by inhibiting Akt activation. Multifactorial strategies for safely opposing β-catenin signaling can be complemented with measures that diminish colonic mutagenesis and DNA hypomethylation - such as avoidance of heme-rich meat and charred or processed meats, consumption of phase II-inductive foods and nutraceuticals (e.g., Crucifera), and assurance of adequate folate status.

The pharmacological effects and safety of the raw and prepared folium of Epimedium brevicornu Maxim. on improving kidney-yang deficiency syndrome and sexual dysfunction

Background: Kidney-Yang deficiency syndrome (KDS) is a group of diseases related to hypothalamic-pituitary-adrenal (HPA) axis and sexual dysfunction. The folium of Epimedium brevicornu Maxim. (FEB) includes raw and prepared slices, named RFEB and PFEB, respectively. PFEB is traditionally believed to be good for tonifying kidney-Yang and improving sexual dysfunction. However, there are few studies comparing the pharmacological effects of RFEB and PFEB, and their underlying mechanisms. In this study, we aimed to compare the effects and safety of RFEB and PFEB on the HPA axis and sexual function. Additionally, the mechanisms of their roles in relation to the neuroendocrine-immune (NEI) network in the KDS model mice were explored. Methods: Male adult C57BL/6 mice were treated with corticosterone to establish a KDS mouse model, and RFEB and PFEB were administered intragastrically. Corticotropin releasing hormone (CRH), adrenocorticotropic hormone (ACTH), cyclic adenosine monophosphate (cAMP), cyclic guanosine monophosphate (cGMP), testosterone levels and oxidative damage indexes were measured. The mRNA and protein levels of CRH and ACTH in hypothalamus and pituitary, endothelial nitric oxide synthase (eNOS) and phosphodiesterase 5 (PDE5) in corpus cavernosum were examined. TNFα, IL-6, NF-κB, eNOS and PDE5 were investigated in mouse corpus cavernosum. Results: Our results showed that PFEB was more effective than RFEB in increasing corticosterone-suppressed ACTH levels, enhancing CRH levels and cAMP/cGMP ratio, and reducing oxidative damage. In vivo, PFEB significantly increased eNOS and inhibited PDE5 expression in corpus cavernosum. PFEB showed stronger protective effect on normal spleen lymphocytes from apoptosis both in vitro and in vivo. Additionally, it noticeably inhibited the levels of inflammatory cytokines in corpus cavernosum. Both RFEB and PFEB were safe and did not cause any clinical signs of toxicity in mice at the dosage of 20 times dosages of that in the Chinese Pharmacopeia. Conclusion: We demonstrated that PFEB was better than RFEB at tonifying the kidney-Yang by comparing their effects on improving the NEI network, which includes the HPA axis, immune system and corpus cavernosum. This study revealed that PFEB could significantly improve the sexual function of KDS mice by regulating the HPA axis and activating the immune system through the NEI network.

An overview of the history, current strategies, and potential future treatment approaches in erectile dysfunction: a comprehensive review

INTRODUCTION

Erectile dysfunction (ED) is one of the most common urologic problems in men worldwide, with an approximately high incidence rate, significantly affecting patients' quality of life and their sexual partners.

OBJECTIVES

Due to the association of this disorder with essential diseases such as cardiovascular disease and diabetes, its prevention and treatment are vital for overall human physiologic and psychological health. Along with reviewing the history of treatment and current methods, we seek new approaches to curb this issue in the future.

METHODS

In this review, investigations were based on the focus of each section's content or conducted on an ad hoc basis. Searches were performed in Scopus and PubMed.

RESULTS

In recent years, many treatments for ED have been reported besides oral administration of phosphodiesterase 5 inhibitors such as sildenafil and tadalafil (approved by the Food and Drug Administration). Common oral medications, intracavernous injections, herbal therapies (eg, herbal phosphodiesterase 5 inhibitors), and topical/transdermal medications are routine ED treatment approaches. Moreover, some novel medications are innovative candidates for completing ED's treatment protocols: stem cell injection, low-intensity extracorporeal shock wave therapy, platelet-rich plasma injection, gene therapy, amniotic fluid matrices, rho-kinase inhibitors, melanocortin receptor antagonists, maxi-K channel activators (ie, large-conductance calcium-activated potassium channels), guanylate cyclase activators, and nitric oxide donors.

CONCLUSION

Due to the importance of this complicated problem in men's society, a faster course of treatment trends toward new methods is needed to increase efficiency. Combining the mentioned treatments and attentively examining their efficacy through programmed clinical trials can be a big step toward solving this global problem.

Icariin: A Promising Natural Product in Biomedicine and Tissue Engineering

Among scaffolds used in tissue engineering, natural biomaterials such as plant-based materials show a crucial role in cellular function due to their biocompatibility and chemical indicators. Because of environmentally friendly behavior and safety, green methods are so important in designing scaffolds. A key bioactive flavonoid of the Epimedium plant, Icariin (ICRN), has a broad range of applications in improving scaffolds as a constant and non-immunogenic material, and in stimulating the cell growth, differentiation of chondrocytes as well as differentiation of embryonic stem cells towards cardiomyocytes. Moreover, fusion of ICRN into the hydrogel scaffolds or chemical crosslinking can enhance the secretion of the collagen matrix and proteoglycan in bone and cartilage tissue engineering. To scrutinize, in various types of cancer cells, ICRN plays a decisive role through increasing cytochrome c secretion, Bax/Bcl2 ratio, poly (ADP-ribose) polymerase as well as caspase stimulations. Surprisingly, ICRN can induce apoptosis, reduce viability and inhibit proliferation of cancer cells, and repress tumorigenesis as well as metastasis. Moreover, cancer cells no longer grow by halting the cell cycle at two checkpoints, G0/G1 and G2/M, through the inhibition of NF-κB by ICRN. Besides, improving nephrotoxicity occurring due to cisplatin and inhibiting multidrug resistance are the other applications of this biomaterial.

Isolation, bioassay and 3D-QSAR analysis of 8-isopentenyl flavonoids from Epimedium sagittatum maxim. as PDE5A inhibitors

BACKGROUND

As known, inhibition of phosphodiesterase 5 (PDE5) has the therapeutic effect on male erectile dysfunction (ED), and the processed folium of Epimedium sagittatum Maxim. (PFES) characterized by 8-isopentenyl flavonoids is a famous herb for treating ED. However, the main flavonoids inhibitory activities, structure-activity relationship (SAR) and signaling pathway have been not systematically studied so that its pharmacodynamic mechanism is unclear.

METHODS

We aimed to initially reveal the PFES efficacy mechanism for treating ED. For the first time, 6 main 8-isopentenyl flavonoids (1-6) from PFES were isolated and identified. Then based on HPLC detection, we proposed a novel method to screen inhibitors among them. We further analyze the three-dimensional quantitative structure-activity relationship (3D-QSAR) for those inhibitors.

RESULTS

The results were verified by cellular effects of the screened flavonoids. Among 6 compounds, Icariin: (1), 2-O''rhamnosylicaridide II (2) and Baohuoside I (3) were identified with significant activities (IC₅₀ = 8.275, 3.233, 5.473 μM). Then 3D-QSAR studies showed that the replacement of C8 with bulky steric groups as isopentenyl, C3 with positive charge groups and C4' with a hydrogen bond acceptor substituent could increase inhibitory effects. In contrast, the substitution of C7 with bulky steric groups or hydrophilic groups tended to decrease the efficacies. And compounds 1, 2, 3 could increase cGMP level and decrease cytoplasmic Ca²⁺ of rat corpus cavernosum smooth muscle cells (CCSMCs)by activating PKG.

CONCLUSION

8-isopentenyl flavonoids could be the main pharmacodynamic substances of PFES in the treatment for ED, and some had significant PDE5A1 inhibitory activities so as to activate cGMP/PKG/Ca²⁺ signaling pathway in CCSMCs, that was related to the substituents at the key sites such as C8, C3, C4' and C7 in the characteristic compounds.

An update on the current status and future prospects of erectile dysfunction following radical prostatectomy

BACKGROUND

Radical prostatectomy (RP) and radiation treatment are standard options for localized prostate cancer. Even though nerve-sparing techniques have been increasingly utilized in RP, erectile dysfunction (ED) due to neuropraxia remains a frequent complication. Erectile function recovery rates after RP remain unsatisfactory, and many men still suffer despite the availability of various therapies.

OBJECTIVE

This systematic review aims to summarize the current treatments for post-RP-ED, assess the underlying pathological mechanisms, and emphasize promising therapeutic strategies based on the evidence from basic research.

METHOD

Evaluation and review of articles on the relevant topic published between 2010 and 2021, which are indexed and listed in the PubMed database.

RESULTS

Phosphodiesterase type 5 inhibitors, intracavernosal and intraurethral injections, vacuum erection devices, pelvic muscle training, and surgical procedures are utilized for penile rehabilitation. Clinical trials evaluating the efficacy of erectogenic drugs in this setting are conflicting and far from being conclusive. The use of androgen deprivation therapy in certain scenarios after RP further exacerbates the already problematic situation and emphasizes the need for effective treatment strategies.

CONCLUSION

This article is a detailed overview focusing on the pathophysiology and mechanism of the nerve injury developed during RP and a compilation of various strategies to induce cavernous nerve regeneration to improve erectile function (EF). These strategies include stem cell therapy, gene therapy, growth factors, low-intensity extracorporeal shockwave therapy, immunophilins, and various pharmacological approaches that have induced improvements in EF in experimental models of cavernous nerve injury. Many of the mentioned strategies can improve EF following RP if transformed into clinically applicable safe, and effective techniques with reproducible outcomes.

Deciphering the myth of icariin and synthetic derivatives in improving erectile function from a molecular biology perspective: a narrative review

Background and Objective

Although epimedium herb (EH) has been widely used in ancient Chinese medicine to enhance sexual activity, its pharmacological mechanism is not clear. Modern studies have shown that epimedium herb is rich in icariin (ICA, a flavonoid compound), and 91.2% of icariin is converted to icariside II (ICA II) by hydrolytic enzymes in intestinal bacteria after oral administration. YS-10 is a synthetic derivative of icariside II. The aim of this review was to summarize the contemporary evidence regarding the pharmacokinetics, therapeutic properties, and molecular biological mechanisms of ICA and some ICA derivatives for erectile dysfunction therapy.

Methods

A detailed search was conducted in the PubMed database using keywords and phrases, such as “icariin” AND “erectile dysfunction”, “icariside II” AND “erectile dysfunction”. The publication time is limited to last 20 years. Articles had to be published in peer reviewed journals.

Key Content and Findings

ICA and its some derivatives showed the specific inhibition on phosphodiesterase type 5 (PDE5) and the promotion of testosterone synthesis. In addition, by regulating various reliable evidence of signaling pathways such as PI3K/AKT, TGFβ1/Smad2, p38/MAPK, Wnt and secretion of various cytokines, ICA and ICA derivatives can activate endogenous stem cells (ESCs) leading to endothelial cell and smooth muscle cell proliferation, nerve regeneration and fibrosis inhibition, repair pathological changes in penile tissue and improve erectile function.

Conclusions

ICA and some of its derivatives could be a potential treatment for restoring spontaneous erections. In addition ICA and his derivatives may also be valuable as a regenerative medicine approach for other diseases, but more clinical and basic researches with high quality and large samples are recommended.

Phenanthrene-enriched extract from Eulophia macrobulbon using subcritical dimethyl ether for phosphodiesterase-5A1 inhibition

Eulophia macrobulbon (E.C.Parish & Rchb.f.) Hook.f. contains a natural PDE5A1 inhibitor, phenanthrene, 1-(4'-hydroxybenzyl)-4,8- dimethoxyphenanthrene-2,7-diol (HDP), a potential agent for the treatment of erectile dysfunction. The aim of this study was to improve the extraction efficiency of HDP from E. macrobulbon by using a more environmentally friendly extraction method, subcritical liquid dimethyl ether extraction (sDME), instead of classical solvent extraction (CSE) and ultrasound-assisted extraction (UAE). The efficiency and quality of the extracts obtained were evaluated using the following criteria: %process yield; solvent amount; extraction time; temperature; %HDP content by LC–MS, bioactivity as inhibition of phosphodiesterase-5A1 (PDE5A1) by radio-enzymatic assay; and chemical profiles by LC-QTOF-MS. sDME provided the highest content of HDP in the extract at 4.47%, much higher than the use of ethanol (0.4–0.5%), ethyl acetate (1.2–1.7%), or dichloromethane (0.7–1.4%). The process yield for sDME (1.5–2.7%) was similar to or lower than the other solvents (0.9–17%), but as long as the process yield is not prohibitively low, the concentration is a more important measure for clinical use. The optimal conditions for sDME extraction were: Extraction time, 40 min; 200% water as co-solvent; sample-to-solvent ratio of 1:8; temperature, 35 °C. Phenanthrene aglycone and glycoside derivatives were the major constituents of the sDME extracts and lesser amounts of phenolic compounds and sugars. The inhibition of PDE5A1 by sDME (IC₅₀ 0.67 ± 0.22 µg/ml) was tenfold more potent than ethanolic extract and other extraction methods, suggesting a high probability of clinical efficacy. Thus, sDME was a more efficient, faster, solvent-saving and environmentally friendly extraction method and more selective for phenanthrene when extracted from E. macrobulbon.

Icariin Protects H9c2 Rat Cardiomyoblasts from Doxorubicin-Induced Cardiotoxicity: Role of Caveolin-1 Upregulation and Enhanced Autophagic Response

Doxorubicin (Doxo) is a widely used antineoplastic drug which often induces cardiomyopathy, leading to congestive heart failure through the intramyocardial production of reactive oxygen species (ROS). Icariin (Ica) is a flavonoid isolated from Epimedii Herba (Berberidaceae). Some reports on the pharmacological activity of Ica explained its antioxidant and cardioprotective effects. The aim of our study was to assess the protective activities of Ica against Doxo-detrimental effects on rat heart-tissue derived embryonic cardiac myoblasts (H9c2 cells) and to identify, at least in part, the molecular mechanisms involved. Our results showed that pretreatment of H9c2 cells with 1 μM and 5 μM of Ica, prior to Doxo exposure, resulted in an improvement in cell viability, a reduction in ROS generation, the prevention of mitochondrial dysfunction and mPTP opening. Furthermore, for the first time, we identified one feasible molecular mechanism through which Ica could exerts its cardioprotective effects. Indeed, our data showed a significant reduction in Caveolin-1(Cav-1) expression levels and a specific inhibitory effect on phosphodiesterase 5 (PDE5a) activity, improving mitochondrial function compared to Doxo-treated cells. Besides, Ica significantly prevented apoptotic cell death and downregulated the main pro-autophagic marker Beclin-1 and LC3 lipidation rate, restoring physiological levels of activation of the protective autophagic process. These results suggest that Ica might have beneficial cardioprotective effects in attenuating cardiotoxicity in patients requiring anthracycline chemotherapy through the inhibition of oxidative stress and, in particular, through the modulation of Cav-1 expression levels and the involvement of PDE5a activity, thereby leading to cardiac cell survival.

Complete biosynthesis of the potential medicine icaritin by engineered Saccharomyces cerevisiae and Escherichia coli

Icaritin is a prenylflavonoid present in the Chinese herbal medicinal plant Epimedium spp. and is under investigation in a phase III clinical trial for advanced hepatocellular carcinoma. Here, we report the biosynthesis of icaritin from glucose by engineered microbial strains. We initially designed an artificial icaritin biosynthetic pathway by identifying a novel prenyltransferase from the Berberidaceae-family species Epimedium sagittatum (EsPT2) that catalyzes the C8 prenylation of kaempferol to yield 8-prenlykaempferol and a novel methyltransferase GmOMT2 from soybean to transfer a methyl to C4'-OH of 8-prenlykaempferol to produce icaritin. We next introduced 11 heterologous genes and modified 12 native yeast genes to construct a yeast strain capable of producing 8-prenylkaempferol with high efficiency. GmOMT2 was sensitive to low pH and lost its activity when expressed in the yeast cytoplasm. By relocating GmOMT2 into mitochondria (higher pH than cytoplasm) of the 8-prenylkaempferol-producing yeast strain or co-culturing the 8-prenylkaempferol-producing yeast with an Escherichia coli strain expressing GmOMT2, we obtained icaritin yields of 7.2 and 19.7 mg/L, respectively. Beyond the characterizing two previously unknown plant enzymes and conducting the first biosynthesis of icaritin from glucose, we describe two strategies of overcoming the widespread issue of incompatible pH conditions encountered in basic and applied bioproduction research. Our findings will facilitate industrial-scale production of icaritin and other prenylflavonoids.

Microbial transformation of icariin and its derivatives

Microbial transformation is an important tool to perform selective conversion of compounds to derivatives which are difficult to produce synthetically. In order to obtain icariside II and icaritin, the active components in Herba Epimedii in vivo, biotransformation studies using microbes as biocatalysts were carried out. Icariside II (2) and icaritin (3) were produced through biotransformation of icariin (1) using the fungi Hormoconis resinae and Mortierella ramanniana var. angulispora in 98% and 92% yields, respectively. In the subsequent transformation studies, 2 was deglycosylated to form 3 by Gliocladium deliquescens, whereas 3 was further converted to a novel compound icaritin-3-O-β-d-glucopyranoside (4) and previously known icaritin-3,7-O-β-d-diglucopyranoside (5) by Mucor hiemalis. Biological evaluation of these compounds using MTT assay exhibited potent cytotoxic activities against human cancer cell lines A549, A375P, and MCF-7, with icariin being the most active, indicating that glycosylation plays a role in the cytotoxic activity.

Natural Molecules as Talented Inhibitors of Nucleotide Pyrophosphatases/Phosphodiesterases (PDEs)

BACKGROUND

Phosphodiesterases (PDEs) are a wide group of enzymes with multiple therapeutic actions, including vasorelaxation, cardiotonic, antidepressant, anti-inflammatory, antithrombotic, anti-spasmolytic, memory-enhancing, and anti-asthmatic. PDEs with eleven subtypes from PDE-1 to PDE-11 typically catalyze the cleavage of the phosphodiester bond and, hence, degrades either cyclic adenosine monophosphate (cAMP) or cyclic guanosine monophosphate (cGMP).

OBJECTIVE

Several selective or non-selective inhibitors of the PDE subtypes are used clinically, i.e. sildenafil, rolipram, cysteine, etc. Recently, interest in plant-based pharmacologically bioactive compounds having potent PDEs inhibitory potential has increased. Purposely, extensive research has been carried out on natural products to explore new inhibitors of various PDEs. Therefore, this review summarizes the published data on natural PDEs inhibitors and their potential therapeutic applications.

METHODS

For this purpose, natural compounds with PDE inhibitory potential have been surveyed through several databases, including PubMed, Web of Sciences (WoS), Scopus, and Google Scholar.

RESULTS

According to a detailed literature survey, the most promising class of herbal compounds with PDE-inhibiting property has been found to belong to phenolics, including flavonoids (luteolin, kaempferol, icariin, etc.). Many other encouraging inhibitors from plants have also been identified, such as coumarins (23, 24) (licoarylcoumarin and glycocoumarin,), saponins ( agapanthussaponins), lignans (31, 33) [(±)-schizandrin and kobusin], terpenes (28, 29, 31) (perianradulcin A, quinovic acid, and ursolic acid), anthraquinones (18, 19) (emodin and chrysophanol), and alkaloids (Sanjoinine-D) (36).

CONCLUSION

In this review, studies have revealed the PDE-inhibitory potential of natural plant extracts and their bioactive constituents in treating various diseases; however, further clinical studies comprising synergistic use of different therapies (synthetic & natural) to acquire multi-targeted results might also be a promising option.

Enhanced Oral Absorption of Icaritin by Using Mixed Polymeric Micelles Prepared with a Creative Acid-Base Shift Method

The purpose of this study was to develop mixed polymeric micelles with high drug loading capacity to improve the oral bioavailability of icaritin with Soluplus^® and Poloxamer 407 using a creative acid-base shift (ABS) method, which exhibits the advantages of exclusion of organic solvents, high drug loading and ease of scaling-up. The feasibility of the ABS method was successfully demonstrated by studies of icaritin-loaded polymeric micelles (IPMs). The prepared IPMs were characterized to have a spherical shape with a size of 72.74 ± 0.51 nm, and 13.18% drug loading content. In vitro release tests confirmed the faster release of icaritin from IPMs compared to an oil suspension. Furthermore, bioavailability of icaritin in IPMs in beagle dogs displayed a 14.9-fold increase when compared with the oil suspension. Transcellular transport studies of IPMs across Caco-2 cell monolayers confirmed that the IPMs were endocytosed in their intact forms through macropinocytosis, clathrin-, and caveolae-mediated pathways. In conclusion, the results suggested that the mixed micelles of Soluplus^® and Poloxamer 407 could be a feasible drug delivery system to enhance oral bioavailability of icaritin, and the ABS method might be a promising technology for the preparation of polymeric micelles to encapsulate poorly water-soluble weakly acidic and alkaline drugs.

Development of Phosphodiesterase-Protein-Kinase Complexes as Novel Targets for Discovery of Inhibitors with Enhanced Specificity

Phosphodiesterases (PDEs) hydrolyze cyclic nucleotides to modulate multiple signaling events in cells. PDEs are recognized to actively associate with cyclic nucleotide receptors (protein kinases, PKs) in larger macromolecular assemblies referred to as signalosomes. Complexation of PDEs with PKs generates an expanded active site that enhances PDE activity. This facilitates signalosome-associated PDEs to preferentially catalyze active hydrolysis of cyclic nucleotides bound to PKs and aid in signal termination. PDEs are important drug targets, and current strategies for inhibitor discovery are based entirely on targeting conserved PDE catalytic domains. This often results in inhibitors with cross-reactivity amongst closely related PDEs and attendant unwanted side effects. Here, our approach targeted PDE–PK complexes as they would occur in signalosomes, thereby offering greater specificity. Our developed fluorescence polarization assay was adapted to identify inhibitors that block cyclic nucleotide pockets in PDE–PK complexes in one mode and disrupt protein-protein interactions between PDEs and PKs in a second mode. We tested this approach with three different systems—cAMP-specific PDE8–PKAR, cGMP-specific PDE5–PKG, and dual-specificity RegA–R_D complexes—and ranked inhibitors according to their inhibition potency. Targeting PDE–PK complexes offers biochemical tools for describing the exquisite specificity of cyclic nucleotide signaling networks in cells.

Preparation, Characterization, and In Vivo Evaluation of Amorphous Icaritin Nanoparticles Prepared by a Reactive Precipitation Technique

Icaritin is a promising anti-hepatoma drug that is currently being tested in a phase-III clinical trial. A novel combination of amorphization and nanonization was used to enhance the oral bioavailability of icaritin. Amorphous icaritin nanoparticles (AINs) were prepared by a reactive precipitation technique (RPT). Fourier transform infrared spectrometry was used to investigate the mechanism underlying the formation of amorphous nanoparticles. AINs were characterized via scanning electron microscopy, X-ray powder diffraction, and differential scanning calorimetry. Our prepared AINs were also evaluated for their dissolution rates in vitro and oral bioavailability. The resultant nanosized AINs (64 nm) were amorphous and exhibited a higher dissolution rate than that derived from a previous oil-suspension formulation. Fourier transform infrared spectroscopy (FTIR) revealed that the C=O groups from the hydrophilic chain of polymers and the OH groups from icaritin formed hydrogen bonds that inhibited AIN crystallization and aggregation. Furthermore, an oral administration assay in beagle dogs showed that C_max and AUC_last of the dried AINs formulation were 3.3-fold and 4.5-fold higher than those of the oil-suspension preparation (p < 0.01), respectively. Our results demonstrate that the preparation of amorphous drug nanoparticles via our RPT may be a promising technique for improving the oral bioavailability of poorly water-soluble drugs.

Medicinal plants as a potential source of Phosphodiesterase-5 inhibitors: A review

ETHNOPHARMACOLOGICAL RELEVANCE

The prevalence and distress caused by erectile dysfunction (ED) to both male and female partners are increasing at a steady rate. ED has now become the most treated sexual disorder for men among young and old age groups due to varying physical and psychological factors. The treatment with synthetic Phosphodiesterase-5 (PDE5) inhibitors are cost-effective but due to adverse effects such as priapism, loss of vision, heart attack and syncope, the daily life patterns of these patients are distressed and hence the need for alternative medicaments or sources are of utmost important. Therefore, the exploration of medicinal plants as PDE5 inhibitors will be worthwhile in tackling the problems as many plant extracts and fractions have been long used as aphrodisiacs and sexual stimulants which may be found to be active against PDE5 enzyme.

AIM OF THE STUDY

To provide a review on the different medicinal herbs traditionally used as natural aphrodisiacs, libido or sexual enhancers which are proven for their PDE5 inhibitory effect.

MATERIALS AND METHODS

Ethnobotanical and scientific information was procured, reviewed and compiled from the literature search of electronic databases and search engines.

RESULTS

A total of 97 medicinal plants exhibiting PDE5 inhibitory effect are reviewed in this paper which is supported by preclinical experimental evidence. Among them, 77 plants have been selected according to their traditional and ethnobotanical uses as aphrodisiacs and the rest are screened according to their effectiveness against predisposing factors responsible for ED and sexual dysfunction such as diabetes and hypertension or due to the presence of phytochemicals having structural similarity towards the identified natural PDE5 inhibitors. In addition, sixteen alkaloids, sixty-one phenolics and eight polycyclic aromatic hydrocarbons have been isolated or identified from active extracts or fractions that are exhibiting PDE5 inhibitory activity. Among them, isoflavones and biflavones are the major active constituents responsible for action, where the presence of prenyl group for isoflavones; and the methoxy group at C-5 position of flavones are considered essential for the inhibitory effect. However, the prenylated flavonol glycoside, Icariin and Icariside II isolated from Epimedium brevicornum Maxim (hory goat weed) are the most effective inhibitor, till date from natural sources. Traditional medicines or formulations containing extracts of Ginkgo biloba L., Kaempferia parviflora Wall. ex Baker, Clerodendrum colebrookianum Walp., Eurycoma longifolia Jack and Vitis vinifera L. are also found to be inhibitors of PDE5 enzyme.

CONCLUSION

The review suggests and supports the rational use of traditional medicines that can be further studied for the development of potential PDE5 inhibitors. Many traditional medicines are still used in various regions of Africa, Asia and South America that are poorly characterized and experimented. Despite the availability of a vast majority of traditional formulations as aphrodisiacs or sexual stimulants, there exists a need for systemic evaluation on the efficacy as well as the mechanism of action of the herbal constituents for the identification of novel chemical moieties that can be further developed for maximum efficacy.

Ferula hermonis: A Review of Current Use and Pharmacological Studies of its Sesquiterpene Ester Ferutinin

Ferula hermonis Boiss, is an endemic plant of Lebanon, locally known as "shilsh Elzallouh". It has been extensively used in the traditional medicine as an aphrodisiac and for the treatment of sexual impotence. Crude extracts and isolated compounds of ferula hermonis contain phytoestrogenic substances having a wide spectrum of in vitro and in vivo pharmacological properties including anti-osteoporosis, anti-inflammatory, anti-microbial and anti-fungal, anti-cancer and as sexual activity enhancer. The aim of this mini-review is to highlight the traditional and novel applications of this plant's extracts and its major sesquiterpene ester, ferutinin. The phytochemical constituents and the pharmacological uses of ferula hermonis crude extract and ferutinin specifically will be discussed.

Cinnamaldehyde mitigates placental vascular dysfunction of gestational diabetes and protects from the associated fetal hypoxia by modulating placental angiogenesis, metabolic activity and oxidative stress

Gestational diabetes mellitus (GDM) is a major pregnancy-related disorder with an increasing prevalence worldwide. GDM is associated with altered placental vascular functions and has severe consequences for fetal growth. There is no commonly accepted medication for GDM due to safety considerations. Actions of the currently limited therapeutic options focus exclusively on lowering the blood glucose level without paying attention to the altered placental vascular reactivity and remodelling. We used the fat-sucrose diet/streptozotocin (FSD/STZ) rat model of GDM to explore the efficacy of cinnamaldehyde (Ci; 20 mg/kg/day), a promising antidiabetic agent for GDM, and glyburide/metformin-HCl (Gly/Met; 0.6 + 100 mg/kg/day), as a reference drug for treatment of GDM, on the placenta structure and function at term pregnancy after their oral intake one week before mating onward. Through genome-wide transcriptome, biochemical, metabolome, metal analysis and histopathology we obtained an integrated understanding of their effects. GDM resulted in maternal and fetal hyperglycemia, fetal hyperinsulinemia and placental dysfunction with subsequent fetal anemia, hepatic iron deficiency and high serum erythropoietin level, reflecting fetal hypoxia. Differentially-regulated genes were overrepresented for pathways of angiogenesis, metabolic transporters and oxidative stress. Despite Ci and Gly/Met effectively alleviated the maternal and fetal glycemia, only Ci offered substantial protection from GDM-associated placental vasculopathy and prevented the fetal hypoxia. This was explained by Ci's impact on the molecular regulation of placental angiogenesis, metabolic activity and redox signaling. In conclusion, Ci provides a dual impact for the treatment of GDM at both maternal and fetal levels through its antidiabetic effect and the direct placental vasoprotective action. Lack of Gly/Met effectiveness to restore it's impaired functionality demonstrates the vital role of the placenta in developing efficient medications for GDM.

Inhibition of Phosphodiesterase 5 Promotes the Aromatase-Mediated Estrogen Biosynthesis in Osteoblastic Cells by Activation of cGMP/PKG/SHP2 Pathway

Mechanical stimulation induces bone growth and remodeling by the secondary messenger, cyclic guanosine 3', 5'-monophosphate (cGMP), in osteoblasts. However, the role of cGMP in the regulation of estrogen biosynthesis, whose deficiency is a major cause of osteoporosis, remains unclear. Here, we found that the prenylated flavonoids, 3-O-methoxymethyl-7-O-benzylicaritin (13), 7-O-benzylicaritin (14), and 4'-O-methyl-8-isopentylkaempferol (15), which were synthesized using icariin analogs, promoted estrogen biosynthesis in osteoblastic UMR106 cells, with calculated EC₅₀ values of 1.53, 3.45, and 10.57 µM, respectively. 14 and 15 increased the expression level of the bone specific promoter I.4-driven aromatase, the only enzyme that catalyzes estrogen formation by using androgens as substrates, in osteoblastic cells. 14 inhibited phosphodiesterase 5 (PDE5), stimulated intracellular cGMP level and promoted osteoblast cell differentiation. Inhibition of cGMP dependent-protein kinase G (PKG) abolished the stimulatory effect of 14 on estrogen biosynthesis and osteoblast cell differentiation. Further, PKG activation by 14 stimulated the activity of SHP2 (Src homology 2 domain-containing tyrosine phosphatase 2), thereby activating Src and ERK (extracellular signal-regulated kinase) signaling and increasing ERK-dependent aromatase expression in osteoblasts. Our findings reveal a previously unknown role of cGMP in the regulation of estrogen biosynthesis in the bone. These results support the further development of 14 as a PKG-activating drug to mimic the anabolic effects of mechanical stimulation of bone in the treatment of osteoporosis.

Botanical Medicine and Natural Products Used for Erectile Dysfunction

INTRODUCTION

Erectile dysfunction is the persistent or recurrent inability to achieve or maintain an erection sufficient for intercourse. Despite various treatment options, not all patients respond adequately and their usefulness is limited by adverse effects and cost. Botanical medicine and natural products have been and continue to be invaluable and untapped sources of new drugs, including potentially those to treat erectile dysfunction.

OBJECTIVES

To review the current literature on botanical medicine traditionally used as aphrodisiacs and treatment of erectile dysfunction, in particular, scientific and clinical investigations that have been performed, possible active phytoconstituents, and mechanisms of action and to identify gaps in current knowledge to better guide future research efforts.

METHODS

A comprehensive literature search was conducted via PubMed, Scopus, Science Direct, and Web of Science on English publications, using various keywords, for example, "herb", "natural product", combined with "erectile dysfunction", "aphrodisiac", and "sexual performance".

RESULTS

369 relevant articles studying medicinal plants used for erectile dysfunction were analyzed. A total of 718 plants from 145 families and 499 genera were reported to be used traditionally as aphrodisiacs and treatment of erectile dysfunction. Top plants used include Pausinystalia johimbe, Lepidium meyenii, and Panax ginseng. Different plant parts are used, with roots being the most common. Less than half of these plants have been evaluated scientifically, using various research methodologies. Clinical trials conducted were collated. Current scientific investigation shows mixed results about their usefulness in enhancing sexual performance. A limited number of studies have attempted to elucidate the mechanisms of action of these medicinal plants.

CONCLUSION

A comprehensive literature review on botanical medicine and natural products used for treatment of erectile dysfunction was successfully conducted. Although medicinal plants serve as a potential source of lead compounds for erectile dysfunction drugs, further studies are warranted to further evaluate their efficacy and safety. SinVJ-E, Anand GS, Koh H-L. Botanical Medicine and Natural Products Used for Erectile Dysfunction. Sex Med Rev 2020;XX:XXX-XXX.

Selective alkylation of β-anhydroicaritine and their biological evaluation on anticancer

A convenient and selective alkylation of icaritin has been developed. The methodology involved initial formation of β-anhydroicaritine (3) under acidic conditions followed by selective methylation at the C-3 position and then alkylation at C-5 position. Several alkylated β-anhydroicaritine derivatives were synthesised using this methodology. These newly synthesised derivatives, especially the compounds 5b, 5c and 5j, significantly suppressed cell proliferation when tested against cancer cell lines in vitro. Compound 5j (R = Bn) exhibited a competitive inhibition against MCF7 in vivo compared to tamoxifen.

Evaluation of the potential aphrodisiac activity of sesquiterpenoids from roots of Ferula huber-morathii Peşmen in male rats

ETHNOPHARMACOLOGICAL RELEVANCE

Several species of Ferula L. genus have been used in traditional Turkish medicine as aphrodisiac to treat male sexual dysfunction. Especially, roots and oleo gum resin of F. elaeochytris Korovin, F. communis L., F. assa-foetida L. and F. gummosa Boiss. were claimed to be used for aphrodisiac activity, menstrual regulation and treatment of gastric pain in Anatolia. Ferula L. is represented by 23 taxa in Turkey, 13 of which are endemic species. F. huber-morathii Peşmen (FHM), an endemic plant, is popularly known as ''helizan, çağşır''.

AIM OF THE STUDY

This study aimed to isolate sesquiterpenoids from the roots of Ferula huber-morathii (FHM) and to confirm their aphrodisiac potential in male rats.

MATERIAL AND METHODS

In a preliminary experiment, the effects of aqueous (H₂O) and chloroform (CHCl₃) extracts of FHM were tested for their potential aphrodisiac activities in male rats. Then, sesquiterpene derivatives were isolated from the active chloroform extract of FHM roots (FHM-R) and characterized (TLC, 1D, 2D NMR, HR-MS and CD). Moreover, some of the isolates with adequate quantities were evaluated for their possible aphrodisiac effects on male rats. Single doses (10 mg/kg BW) of sildenafil citrate (SC, positive control), gummosin, mogoltavidin, deacetylkellerin, ferukrin acetate with kellerin, elaeochytrin-A and ferutinin were administered orally by gavages to male Wistar albino rats. Mount latency (ML), mount frequency (MF), intromission latency (IL), intromission frequency (IF), ejaculation latency (EL) and postejaculatory interval (PEI) were studied. In addition, copulatory efficiency (CE) and intercopulatory efficiency (ICE) were calculated.

RESULTS

The preliminary experiment revealed that the chloroform extract was the main source of the active compounds as it showed the higher aphrodisiac activity while the aqueous extract was found to be inactive. Eleven sesquiterpene derivatives, viz. gummosin, mogoltavidin, farnesiferol A, deacetylkellerin, ferukrin acetate, kellerin, teuclatriol, feruhermonin C, ferutinin, elaeochytrin A and teferidin, were isolated from the FHM-CHCl₃ extract. Oral administration of deacetylkellerin, elaeochytrin-A and ferutinin significantly increased MF and IF. The ML and IL were significantly reduced, and ejaculation latencies were prolonged. Administration of these sesquiterpenoids also reduced the PEI. The present results revealed that ferutinin was the most effective aphrodisiac compound compared to other sesquiterpenoids. The results of 10 mg/kg of ferutinin are comparable to SC, the positive control. The results revealed that gummosin, mogoltavidin and ferukrin acetate with kellerin did not significantly alter the aphrodisiac parameters.

CONCLUSIONS

This study has established that the CHCl₃ extract of FHM root contains sesquiterpene derivatives, especially coumarin ethers and benzoic esters. Findings of the present study demonstrate that the chloroform extract and some of the sesquiterpene derivatives significantly stimulates sexual behavior in male rats, thus suggesting that F. huber-morathii possesses an aphrodisiac activity.

Therapeutic Potential of Phosphodiesterase Inhibitors against Neurodegeneration: The Perspective of the Medicinal Chemist

Increasing human life expectancy prompts the development of novel remedies for cognitive decline: 44 million people worldwide are affected by dementia, and this number is predicted to triple by 2050. Acetylcholinesterase and N-methyl-d-aspartate receptors represent the targets of currently available drugs for Alzheimer’s disease, which are characterized by limited efficacy. Thus, the search for therapeutic agents with alternative or combined mechanisms of action is wide open. Since variations in 3′,5′-cyclic adenosine monophosphate, 3′,5′-cyclic guanosine monophosphate, and/or nitric oxide levels interfere with downstream pathways involved in memory processes, evidence supporting the potential of phosphodiesterase (PDE) inhibitors in contrasting neurodegeneration should be critically considered. For the preparation of this Review, more than 140 scientific papers were retrieved by searching PubMed and Scopus databases. A systematic approach was adopted when overviewing the different PDE isoforms, taking into account details on brain localization, downstream molecular mechanisms, and inhibitors currently under study, according to available in vitro and in vivo data. In the context of drug repurposing, a section focusing on PDE5 was introduced. Original computational studies were performed to rationalize the emerging evidence that suggests the role of PDE5 inhibitors as multi-target agents against neurodegeneration. Moreover, since such compounds must cross the blood–brain barrier and reach inhibitory concentrations in the central nervous system to exert their therapeutic activity, physicochemical parameters were analyzed and discussed. Taken together, literature and computational data suggest that some PDE5 inhibitors, such as tadalafil, represent promising candidates.

Molecular and cellular basis of the anticancer activity of the prenylated flavonoid icaritin in hepatocellular carcinoma

The prenylated flavonoid icaritin (ICT) is currently undergoing phase 3 clinical trial for the treatment of advanced hepatocellular carcinoma (HCC), based on a solid array of preclinical and clinical data. The antitumor activity originates from the capacity of the drug to modulate several signaling effectors in cancer cells, mainly the estrogen receptor splice variant ERα36, the transcription factors STAT3 and NFκB, and the chemokine receptor CXCR4. Recent studies have implicated additional components, including different microRNAs, the generation of reactive oxygen species and the targeting of sphingosine kinase-1. ICT also engages the RAGE-HMGB1 signaling route and modulates the apoptosis/autophagy crosstalk to promote its anticancer activity. In addition, ICT exerts profound changes on the tumor microenvironment to favor an immune-response. Collectively, these multiple biochemical and cellular characteristics confer to ICT a robust activity profile which can be exploited to treat HCC, as well as other cancers, including glioblastoma and onco-hematological diseases such as chronic myeloid leukemia. This review provides an update of the pharmacological properties of ICT and its metabolic characteristics. It also addresses the design of derivatives, including both natural products and synthetic molecules, such as SNG1153 also in clinical trial. The prenylated flavonoid ICT deserves attention as a multifunctional natural product potentially useful to improve the treatment of advanced hepatocellular carcinoma.

At-line LC-QTOF-MS micro-fractionation of Derris scandens (Roxb.) Benth, coupled to radioassay for the early identification of PDE5A1 inhibitors

INTRODUCTION

Chromatographic techniques coupled with bioassays are popularly used for the detection of bioactive compounds in natural products. In this study phytochemicals responsible for showing Phosphodiesterase type 5 (PDE5) inhibitory activity in Derris scandens were studied using at-line method.

OBJECTIVE

The objective of this study was to develop an at-line liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) micro-fractionation method for rapid separation and identification of PDE5A1 inhibitors in 95% ethanolic extract of D. scandens.

METHODOLOGY

Initially, the correlation between LC-MS and PDE5A1 inhibitory activity was studied using three concentrations of 1:1 mixture of sildenafil and derrisisoflavone A; PDE5A1 inhibitors. The mixture was separated by high-performance liquid chromatography (HPLC) column and the eluent was split into two flows in the ratio of 1:9. The major part was collected in a 96-well plate, in each well consecutively every 30 s. The minor part was fed into an electrospray ionisation (ESI)-QTOF-MS system. After subsequent solvent removal, the collected micro-fractions were subjected to radioassay to determine PDE5A1 inhibition.

RESULTS

The result showed, PDE5A1 inhibitory activities of the micro-fractions were observed in a dose response manner and found to be in agreement with an off-line study. Similarly, 95% ethanolic extract of D. scandens was subjected to the at-line LC-QTOF-MS micro-fractionation developed, resulting in separation and tentative identification of 25 compounds with PDE5A1 inhibitory activity. Most of the compounds contained prenylated isoflavone skeleton. Additionally, the active micro-fractions also showed selectivity on PDE5A1 over PDE6 and PDE1B.

CONCLUSION

Our results demonstrated that the at-line coupled LC-QTOF-MS micro-fractionation with PDE5A1 inhibitory assay is a valuable tool for identifying PDE5A1 inhibitors from complex extracts.

Current Concepts on the Reno-Protective Effects of Phosphodiesterase 5 Inhibitors in Acute Kidney Injury: Systematic Search and Review

Acute kidney injury (AKI) is associated with increased morbidity, prolonged hospitalization, and mortality, especially in high risk patients. Phosphodiesterase 5 inhibitors (PDE5Is), currently available as first-line therapy of erectile dysfunction in humans, have shown a beneficial potential of reno-protection through various reno-protective mechanisms. The aim of this work is to provide a comprehensive overview of the available literature on the reno-protective properties of PDE5Is in the various forms of AKI. Medline was systematically searched from 1946 to November 2019 to detect all relevant animal and human studies in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. In total, 83 studies were included for qualitative synthesis. Sildenafil is the most widely investigated compound (42 studies), followed by tadalafil (20 studies), icariin (10 studies), vardenafil (7 studies), zaprinast (4 studies), and udenafil (2 studies). Even though data are limited, especially in humans with inconclusive or negative results of only two clinically relevant studies available at present, the results of animal studies are promising. The reno-protective action of PDE5Is was evident in the vast majority of studies, independently of the AKI type and the agent applied. PDE5Is appear to improve the renal functional/histopathological alternations of AKI through various mechanisms, mainly by affecting regional hemodynamics, cell expression, and mitochondrial response to oxidative stress and inflammation.

Icariside II, a PDE5 Inhibitor, Suppresses Oxygen-Glucose Deprivation/Reperfusion-Induced Primary Hippocampal Neuronal Death Through Activating the PKG/CREB/BDNF/TrkB Signaling Pathway

Background

Ischemic stroke remains the leading cause of death and adult disability. Cerebral ischemic/reperfusion (I/R) injury is caused by ischemic stroke thereafter aggravates overwhelming neuronal apoptosis and even the death of neurons. Of note, hippocampus is more susceptive to cerebral I/R injury than the other brain region. This study was designed to explore the effects and mechanism of icariside II (ICS II), a pharmacologically active compound exists in herbal Epimedii with previous study-proved as a phosphodiesterase 5 (PDE5) inhibitor, on the oxygen glucose deprivation/reoxygenation (OGD/R)-induced primary hippocampal neurons injury.

Methods

Effects of ICS II on primary hippocampal neuronal impairment and apoptosis induced by OGD/R were examined by MTT, lactate dehydrogenase (LDH) release, TUNEL staining, and flow cytometry, respectively. Activation of memory-related signaling pathways was measured using Western blot analysis. The direct interaction between ICS II and PDE5 was further evaluated by molecular docking.

Results

ICS II (12.5, 25, 50 μM) markedly abrogated OGD/R-induced hippocampal neuronal death as suggested by the increase in neurons viability and the decrease in cellular LDH release. Furthermore, ICS II not only effectively decreased the protein expression and activity of PDE5, restored the 3′5′-cyclic guanosine monophosphate (cGMP) level and its downstream target protein kinase G (PKG) activity but also increased the phosphorylation of cAMP response element binding protein (CREB) level, expressions of brain derived neurotrophic factor (BDNF), and tyrosine protein kinase B (TrkB). Mechanistically, the inhibitory effects of ICS II were abrogated by Rp-8-Br-cGMP (a PKG inhibitor) or ANA-12 (a TrkB inhibitor), which further confirmed that the favorable effects of ICS II were attributed to its activation of the PKG/CREB/BDNF signaling pathways. Intriguingly, ICS II might effectively bind and inhibited PDE5 activity as demonstrated by relatively high binding scores (−6.52 kcal/mol).

Conclusions

ICS II significantly rescues OGD/R-induced hippocampal neuronal injury. The mechanism is, at least partly, due to inhibition of PDE5 and activation of PKG/CREB/BDNF/TrkB signaling pathway. Hence it is thought that ICS II might be a potential naturally PDE5 inhibitor to combat cerebral I/R injury.

Natural product-derived icaritin exerts anti-glioblastoma effects by positively modulating estrogen receptor β

Glioblastoma is the most common malignancy of the central nervous system, and patients typically have a poor prognosis. Previous studies indicate a gender bias in the development of glioblastoma; women are at a lower risk compared with men, suggesting that estrogen may confer protective effects. Icaritin, a prenylflavonoid derivative from a Chinese herb of the Epimedium genus, selectively regulates the estrogen receptor (ER) and possesses anti-cancer properties. The aim of the present study was to investigate the protective effects of icaritin on glioblastoma and its underlying mechanisms, with a particular focus on its association with the ER. The results demonstrated that icaritin inhibited the growth of C6 and U87-MG glioblastoma cells in a dose- and time-dependent manner. At a concentration of 12.5 µM, icaritin induced apoptosis, which was characterized by the increased expression of the cleaved forms of caspases 3, 7, 8 and 9 and poly (ADP-ribose) polymerase, downregulation of BCL2 apoptosis regulator and upregulation of BCL2-associated X, apoptosis regulator expression. Additionally, icaritin inhibited the migration of C6 and U87-MG cells. The protein expression levels of matrix metalloproteinase (MMP)-2 and MMP-9 were also downregulated following icaritin treatment. Furthermore, icaritin treatment increased the expression of estrogen receptor (ER)β and the phosphatase and tensin (PTEN) homolog oncoprotein, thus reducing the expression of downstream targets of PTEN; protein kinase B (Akt) and phosphorylated Akt. Subsequent experiments demonstrated that icaritin cooperates with 17β-estradiol to inhibit the growth of glioblastoma cells, and the inhibition of ERβ with the ERβ-specific antagonist ICI 182,780, attenuated the anti-glioblastoma effects of icaritin. In conclusion, the results of the present study demonstrate that the anti-glioblastoma effects of icaritin may be mediated by its modulation of ERβ.

Combinatorial library generation, molecular docking and molecular dynamics simulations for enhancing the isoflavone scaffold in phosphodiesterase inhibition

Isoflavones are listed among the most widely studied natural compounds in light of their several biological properties, one of which consists in their ability to inhibit phosphodiesterases (PDEs).

Evaluation of relaxant responses properties of cinnamon essential oil and its major component, cinnamaldehyde on human and rat corpus cavernosum

Cinnamomum cassia (Cinnamon) is a well-known traditional medicine with therapeutic benefits for centuries. We evaluated the effects of cinnamon essential oil (CEO) and its main component cinnamaldehyde (CA) on human corpus cavernosum (HCC) and rat CC. The essential oil of cinnamon was analyzed for the confirmation of the oil profile. HCC specimens from patients undergoing penile prosthesis surgery (age 48-69 years) were utilized for functional studies. In addition, erectile responses in anesthetized control and diabetic rats were evaluated in vivo after intracavernosal injection of CEO and CA, and rat CC strips were placed in organ baths. After precontraction with phenylephrine (10μM), relaxant responses to CEO and CA were investigated. CA (96.9%) was found as the major component. The maximum relaxation responses to CEO and CA were 96.4±3.5% and 96.0±5.0% in HCC and 97.5±5.5% and 96.8±4.8% in rat CC, respectively. There was no difference between control and diabetic rats in relaxation responses to CEO and CA. The relaxant responses obtained with essential oil and CA were not attenuated in the presence of nitric oxide synthase (NOS) inhibitor, and soluble guanylate cyclase inhibitor (sGS) in CC. In vivo, erectile responses in diabetic rats were lower than in control rats, which was restored after intracavernosal injection of CEO and CA. CEO and CA improved erectile function and relaxation of isolated strips of rat CC and HCC by a NO/cGMP-independent mechanism. Further investigations are warranted to fully elucidate the restorative effects of CEO and CA on diabetic erectile dysfunction.

Exploration of icariin analog structure space reveals key features driving potent inhibition of human phosphodiesterase-5

The natural product icariin inhibits human phosphodiesterase-5 (PDE5) and represents a unique pharmacophore for treating erectile dysfunction, pulmonary hypertension, and other diseases. In this study, we explore the available icariin-derived chemical scaffolds through medicinal chemistry to develop novel icariin PDE5 inhibitors with improved potency and specificity. We synthesized six novel semi-synthetic icariin analogs as well as three naturally occurring icariin analogs, and characterized the structure-activity relationship in the context of human PDE5 inhibition using in vitro enzyme inhibition and kinetics assays and molecular modeling. Mammalian-cell-based assays and in vitro enzyme inhibition assays against human PDE6C further helped to identify the most potent and selective icariin analogs. Our results reveal the synergistic contribution of functional groups at the C3 and C7 positions of the icariin backbone towards PDE5 inhibition. Whereas a hydrophobic and flexible alkanol group at the C7 position is sufficient to enhance icariin analog potency, combining this group with a hydrophilic sugar group at the C3 position leads to further enhancement of potency and promotes specificity towards PDE5 versus PDE6C. In particular, compounds 3 and 7 exhibit K_i values of 0.036 ± 0.005 μM and 0.036 ± 0.007 μM towards PDE5 respectively, which are approaching those of commercial PDE5 inhibitors, and can effectively reduce GMP levels in cultured human BJ-hTERT cells. This study identifies novel icariin analogs as potent and selective PDE5 inhibitors poised to become lead compounds for further pharmaceutical development.

Human Safety and Pharmacokinetics Study of Orally Administered Icariin: Randomized, Double-Blind, Placebo-Controlled Trial

Preclinical literature suggests that icariin, a flavonoid found in Epimedium, may have potential for medical and psychiatric conditions. The objective of this study was to examine the safety, tolerability, and pharmacokinetics of orally administered icariin at doses of 100 to 1,680 mg/day in 24 healthy adult participants. Cognition, mood, and side effects were assessed over 5 days. Multiple blood samples were obtained over 24 hours to assess bioavailability and pharmacokinetics. Data were analyzed using a Wilcoxon signed rank test and Mann-Whitney U test. At all doses, either very low or undetectable blood levels of icariin were observed, demonstrating the low bioavailability of the oral formulation and preventing a determination of pharmacokinetic properties. No significant between-group differences were observed on side effect scales, either by self-report, or on cognitive assessments. A statistically significant, but not clinically significant, increase in self-reported depressive symptom severity was observed with icariin relative to placebo. Tolerability of icariin was good except at the highest dose. Two participants receiving 1,680 mg of icariin discontinued the study drug due to gastrointestinal symptoms. Bioavailability of oral icariin appears to be low at all doses tested. Although icariin appears generally to have a favorable tolerability profile, the highest doses may be associated with gastrointestinal distress. Different drug formulation and delivery method may be needed to assess the pharmacokinetic profile of icariin adequately.

Identification of Quinone Methide Intermediate Resulting from Metabolic Activation of Icaritin in Vitro and in Vivo

Many herbal medicines such as epimedium have been reported to cause adverse effects, and icaritin is the common aglycone of many glucosides in epimedium. Our present work aimed at the clarification of the metabolic activation of icaritin possibly responsible for the adverse effects of epimedium. A quinone methide metabolite (M1) was detected in icaritin-fortified microsomal incubations. A glutathione (GSH) conjugate (M2) and N-acetyl-l-cysteine (NAC) conjugate (M3) derived from icaritin were observed in GSH/NAC-supplemented rat/human liver microsomal incubations. CYP3A family was the predominant enzyme catalyzing the bioactivation of icaritin. In conclusion, sufficient evidence indicates the metabolic activation of icaritin to quinone methide metabolite.

Male sexual enhancers from the Peruvian Amazon

ETHNOPHARMACOLOGICAL RELEVANCE

Selected Peruvian Amazon plants are macerated into sugar cane distillates to prepare alcoholic beverages used to improve male sexual performance. The tree bark from Campsiandra angustifolia Spruce ex Benth (Fabaceae), Swartzia polyphylla DC (Fabaceae), Minquartia guianensis Aubl. (Olacaceae) and Thynantus panurensis (Bureau) Sandwith (Bignoniaceae) usually are used as crude drugs in mixtures of several ingredients.

AIM OF STUDY

Describe the chemical composition of the most traded traditional male enhancer beverages, namely "Levántate Lazaro" and "Siete veces sin sacarla", and their single crude drug constituents, as well as their inhibitory activity towards the enzyme phosphodiesterase-5. The presence of pro-sexual drugs such as Sildenafil® and derivatives was assessed in the samples.

MATERIALS AND METHODS

Single plant constituents and the preparation mixtures were purchased in the Mercado Belen (Iquitos, Peru). Chemical profiling was carried out by HPLC-DAD-ESI-MS/MS. The extracts were assessed for phosphodiesterase-5 inhibition. The occurrence of pro-sexual drugs was determined by HPLC-DAD-ESI-MS/MS.

RESULTS

Chemical profiling allowed the identification of condensed tannins as the main constituents of C. angustifolia and S. polyphylla, hydrolysable tannins for M. guianensis, and C-glycosides for T. panurensis. The traditional preparations showed similar composition compared to the crude drugs. At 200 µg/mL, the traditional preparation "Levántate Lázaro" and "Siete veces sin sacarla" inhibited the phosphodiesterase-5 by 49.88% and 27.90%, respectively. No adulterations with pro-sexual drugs were found in the samples. From the crude drugs, low effect was found for the extracts of S. polyphylla and T. panurensis and high activity for C. angustifolia which inhibited the enzyme by 89.37% and 81.32% at 200 and 100 µg/mL, respectively.

CONCLUSION

The traditional preparations used to improve sexual performance in the Peruvian Amazon showed activity as phosphodiesterase-5 inhibitors. The most active ingredient of the traditional preparations was C. angustifolia, with some contribution from T. panurensis. These results encourage additional studies, including animal models to confirm the male enhancer effect of the preparations.

Phenolic-rich extracts of Eurycoma longifolia and Cylicodiscus gabunensis inhibit enzymes responsible for the development of erectile dysfunction and are antioxidants

BACKGROUND

Herbs have been used from ages to manage male sexual dysfunction. Hence, this study sought to investigate the effects of Eurycoma longifolia (EL) and Cylicodiscus gabunensis (CG) stem bark extracts on some enzymes implicated in erectile dysfunction in vitro.

METHODS

The extracts were prepared, and their effects on phosphodiesterase-5 (PDE-5), arginase, and angiotensin-1-converting enzyme (ACE) as well as pro-oxidant-induced lipid peroxidation were assessed. Furthermore, phenolic contents were determined, and their components were characterized and quantified using high-performance liquid chromatography with diode array detector (HPLC-DAD).

RESULTS

The results revealed that the extracts inhibited PDE-5, arginase, and ACE in a concentration-dependent manner. However, IC50 values revealed that CG had higher inhibitory potential on PDE-5 (IC50=204.4 μg/mL), arginase (IC50=39.01 μg/mL), and ACE (IC50=48.81 μg/mL) than EL. In addition, the extracts inhibited pro-oxidant-induced lipid peroxidation in penile tissue homogenate. HPLC-DAD analysis showed that CG is richer in phenolic compounds than EL, and this could be responsible for higher biological activities observed in CG than EL.

CONCLUSIONS

Hence, the observed antioxidant property and inhibitory action of CG and EL on enzymes relevant to erectile dysfunction in vitro could be part of possible mechanisms underlying their involvement in traditional medicine for the management of male sexual dysfunction.

Parquetina nigrescens leaves: chemical profile and influence on the physical and biochemical indices of sexual activity of male Wistar rats

OBJECTIVE

The leaves of Parquetina nigrescens have been claimed in folk medicine to be useful for managing sexual dysfunction, but there is inadequate scientific evidence for this claim. This investigation was conducted to assess the effects of aqueous leaf extract of Parquetina nigrescens (AEPN) in rats induced with sexual dysfunction.

METHODS

Male rats were allocated into various groups after being induced into sexual dysfunction with paroxetine hydrochloride. The groups were treated with distilled water, PowMaxM (reference drug), and the AEPN at 20, 40 and 80 mg/kg body weight (BW) respectively for 7 d. Frequencies of mount (MF), intromission (IF), ejaculation (EF), as well as latencies of mount (ML), intromission (IL) and post-ejaculatory interval (PEI) were progressively monitored with receptive female rats on days 1, 3 and 7. The precentage of mounted, intromitted, and ejaculated rats, intromission ratio (IR), copulatory efficiency (CE) and intercopulatory interval (ICI) were also computed. Standard methods were employed to determine the levels of serum luteinizing and follicle stimulating hormones (LH and FSH), testosterone, nitric oxide (NO) and the activity of phosphodiesterase V (PDE5).

RESULTS

The plant contained alkaloids, saponins, flavonoids, cardiac glycosides, steroids, tannins, phlobatannins, cardenolides, phenolics, anthraquinones and triterpenes with alkaloids (2.32 mg/g) occurring in greatest quantity while flavonoids, anthraquinones and cardenolides (0.01 mg/g, each) were the least. All the 20 standard amino acids were detected in the plant leaf, with the lowest concentration being 0.30 mg/g for methionine and the highest being 2.12 mg/g for cysteine. Furthermore, P. nigrescens leaves contained Na, K, Fe, Mg, Zn, Ca, Cu, Mn, P, Pb, Cd, Ni, Cr, and Co, with Fe present in the highest and Co the lowest concentrations. Paroxetine significantly (P<0.05) reduced MF, IF, EF, percentage mounted , intromitted, ejaculated, IR, CE, serum testosterone, LH, FSH and NO, while ML, IL, PEI, IF and PDE5 were significantly (P<0.05) increased and/or prolonged. The AEPN significantly reversed these paroxetine-treatment-related alterations with most profound activity at the highest dose of 80 mg/kg BW, similar to that of the PowMaxM-treated animals.

CONCLUSION

The AEPN restored both the physical and biochemical indices of male sexual activity/competence via changes in reproductive hormones, NO and PDE5 activity. The pro-sexual activity, attributed to a myriad of mineral, amino acid and secondary metabolite constituents, was best at 80 mg/kg BW of AEPN.

Evaluation of selected traditional Chinese medical extracts for bone mineral density maintenance: A mechanistic study

Objective

To investigate the development of a minimal traditional Chinese medicine (TCM) formula using selected TCM ingredients and evaluating their biological activity with bone-specific in vitro tests. Finally, determining if the minimal formula can maintain bone mineral density (BMD) in a low bone mass (LBM)/osteoporosis (OP) model system.

Methods and results

Sixteen different TCM plant extracts were tested for estrogenic, osteogenic and osteoclastic activities. Despite robust activation of the full-length estrogen receptors α and β by Psoralea corylifolia and Epimedium brevicornu, these extracts do not activate the isolated estrogen ligand binding domains (LBD) of either ERα or ERβ; estrogen (17-β estradiol) fully activates the LBD of ERα and ERβ. E. brevicornu and Drynaria fortunei extracts activated cyclic AMP response elements (CRE) individually and when combined these ingredients stimulated the production of osteoblastic markers Runx2 and Bmp4 in MC3T3-E1 cells. E. brevicornu, Salvia miltiorrhiza, and Astragalus onobrychis extracts inhibited the Il-1β mediated activation of NF-κβ and an E. brevicornu/D. fortunei combination inhibited the development of osteoclasts from precursor cells. Further, a minimal formula containing the E. brevicornu/D. fortunei combination with or without a third ingredient (S. miltiorrhiza, Angelica sinensis, or Lycium barbarum) maintained bone mineral density (BMD) similar to an estradiol-treated control group in the ovariectomized rat; a model LBM/OP system.

Conclusion

A minimal formula consisting of TCM plant extracts that activate CRE and inhibit of NF-κβ activation, but do not behave like estrogen, maintain BMD in a LBM/OP model system.

The roles of breast cancer resistance protein (BCRP/ABCG2) and multidrug resistance-associated proteins (MRPs/ABCCs) in the excretion of cycloicaritin-3-O-glucoronide in UGT1A1-overexpressing HeLa cells

Cycloicaritin is a bioactive natural phenolic compound from Epimedium species. However, the glucuronidation and excretion which would influence oral bioavailability and pharmacokinetics of cycloicaritin still remain unknown. Here we aimed to establish UGT1A1 stably transfected HeLa cells, and to determine the contributions of BCRP and MRPs transporters to excretion of cycloicaritin-3-O-glucuronide. First, β-estradiol was used to validate the expression of active UGT1A1 protein in engineered HeLa1A1 cells. Furthermore, Ko143 (5 and 20 μM) led to a significant decrease (42.4%-63.8%, p < 0.01) in CICT-3-G excretion and obvious accumulation (19.7%-54.2%, p < 0.05) of intracellular CICT-3-G, while MK571 (5 and 20 μM) caused a significant reduction (46.8%-64.8%, p < 0.05) in the excretion and obvious elevation (50.7%-85.2%, p < 0.01) of intracellular level of CICT-3-G. Furthermore, BCRP knocked-down brought marked reduction in excretion rates of CICT-3-G (26.0%-42.2%, p < 0.01), whereas MRP1 and MRP4-mediated silencing led to significant decrease in the excretion of CICT-3-G (23.8%-35.4%, p < 0.05 for MRP1 and 11.9%-16.0%, p < 0.05 for MRP4). By contrast, neither CICT-3-G excretion nor CICT-3-G accumulation altered in MRP3 knocked-down cells as compared to scramble cells. Taken together, BCRP, MRP1 and MRP4 were identified as the most important contributors for CICT-3-G excretion. Meanwhile, the UGT1A1 modified HeLa cells were a simple and practical tool to study UGT1A1-mediated glucuronidation and to characterize BCRP and MRPs-mediated glucuronide transport at a cellular level.