Oral absorption and excretion of icaritin, an aglycone and also active metabolite of prenylflavonoids from the Chinese medicine Herba Epimedii in rats

New insights into the anticancer therapeutic potential of icaritin and its synthetic derivatives

Icaritin is a natural prenylated flavonoid derived from the Chinese herb Epimedium. The compound has shown antitumor effects in various cancers, especially hepatocellular carcinoma (HCC). Icaritin exerts its anticancer activity by modulating multiple signaling pathways, such as IL-6/JAK/STAT3, ER-α36, and NF-κB, affecting the tumor microenvironment and immune system. Several clinical trials have evaluated the safety and efficacy of icaritin in advanced HCC patients with poor prognoses, who are unsuitable for conventional therapies. The results have demonstrated that icaritin can improve survival, delay progression, and produce clinical benefits in these patients, with a favorable safety profile and minimal adverse events. Moreover, icaritin can enhance the antitumor immune response by regulating the function and phenotype of various immune cells, such as CD8+ T cells, MDSCs, neutrophils, and macrophages. These findings suggest that icaritin is a promising candidate for immunotherapy in HCC and other cancers. However, further studies are needed to elucidate the molecular mechanisms and optimal dosing regimens of icaritin and its potential synergistic effects with other agents. Therefore, this comprehensive review of the scientific literature aims to summarize advances in the knowledge of icaritin in preclinical and clinical studies as well as the pharmacokinetic, metabolism, toxicity, and mechanisms action to recognize the main challenge, gaps, and opportunities to develop a medication that cancer patients can use. Thus, our main objective was to clarify the current state of icaritin for use as an anticancer drug.

Dietary glucosinolates derived isothiocyanates: chemical properties, metabolism and their potential in prevention of Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent form of dementia affecting millions of people worldwide. It is a progressive, irreversible, and incurable neurodegenerative disorder that disrupts the synaptic communication between millions of neurons, resulting in neuronal death and functional loss due to the abnormal accumulation of two naturally occurring proteins, amyloid β (Aβ) and tau. According to the 2018 World Alzheimer's Report, there is no single case of an Alzheimer's survivor; even 1 in 3 people die from Alzheimer's disease, and it is a growing epidemic across the globe fruits and vegetables rich in glucosinolates (GLCs), the precursors of isothiocyanates (ITCs), have long been known for their pharmacological properties and recently attracted increased interest for the possible prevention and treatment of neurodegenerative diseases. Epidemiological evidence from systematic research findings and clinical trials suggests that nutritional and functional dietary isothiocyanates interfere with the molecular cascades of Alzheimer's disease pathogenesis and prevent neurons from functional loss. The aim of this review is to explore the role of glucosinolates derived isothiocyanates in various molecular mechanisms involved in the progression of Alzheimer's disease and their potential in the prevention and treatment of Alzheimer's disease. It also covers the chemical diversity of isothiocyanates and their detailed mechanisms of action as reported by various in vitro and in vivo studies. Further clinical studies are necessary to evaluate their pharmacokinetic parameters and effectiveness in humans.

Absorption, tissue distribution, and excretion of glycycoumarin, a major bioactive coumarin from Chinese licorice (Glycyrrhiza uralensis Fisch)

Licorice (Glycyrrhiza uralensis Fisch) is a natural plant resource widely used as a food and herbal medication in China. Glycycoumarin (GCM) is a major coumarin in licorice that possesses several biological activities. However, little is known about its pharmacokinetic profile. The present study aimed to describe the oral absorption, tissue distribution, and excretion of GCM in rats. Free (parent drug) and/or total (parent drug plus the glucuronidated metabolite) GCM in biological samples was quantified before and after the hydrolysis reaction with β-glucuronidase using a reliable LC-MS/MS method. The results indicated that GCM was rapidly absorbed and transformed into its conjugated metabolites after administration. Free GCM plasma concentrations after i. v. (10 mg/kg) administration quickly decreased with an average t_1/2,λz of 0.71 h, whereas the total GCM concentration reduced slowly with a t_{1/2, λz} of 2.46 h. The area under the curve of glucuronidated metabolites was approximately four-times higher than that of free GCM. Presumably, because of hepatic and/or intestinal tract first-pass metabolism, GCM exhibited a poor bioavailability of 9.22%, as estimated from its total plasma concentration. Additionally, GCM was distributed rapidly and widely in various tissues except the brain. The liver had the highest concentration; further, GCM was promptly eliminated from test tissues after intraperitoneal (20 mg/kg) administration, but only a small amount of GCM was excreted via bile and urine. Overall, GCM is absorbed and rapidly transformed into its conjugated metabolites with low bioavailability; further, it is distributed in various tissues, except the brain. These pharmacokinetic results are helpful for better understanding the characteristics and pharmacological effects of GCM.

Icaritin: A phytomolecule with enormous pharmacological values

Pharmacological studies on flavonoids have always drawn much interest for many years. Icaritin (ICT), a representative flavone containing an 8-prenyl group, is a principal compound detected in medicinal plants of the genus Epimedum, the family Berberidaceae. Experimental results in the phytochemistry and pharmacology of this molecule are abundant now, but a deep overview has not been carried out. The goal of this review is to provide an insight into the natural observation, biosynthesis, biotransformation, synthesis, pharmacology, and pharmacokinetics of prenyl flavone ICT. The relevant data on ICT was collected from bibliographic sources, like Google Scholar, Web of Science, Sci-Finder, and various published journals. "Icaritin" alone or in combination is the main keyword to seek for references, and references have been updated till now. ICT is among the characteristic phytomolecules of Epimedum plants. Bacteria monitored its biosynthesis and biotransformation, while this agent was rapidly synthesized from phloroglucinol by microwave-assistance Claisen rearrangement. ICT is a potential agent in numerous in vitro and in vivo pharmacological records, which demonstrated its role in cancer treatments via apoptotic-related mechanisms. It also brings in various health benefits since it reduced harmful effects on the liver, lung, heart, bone, blood, and skin, and improved immune responses. Pharmacokinetic outcomes indicated that its metabolic pathway involved hydration, hydroxylation, dehydrogenation, glycosylation, and glucuronidation. Molecule mechanisms of action at a cellular level are predominant, but clinical studies are expected to get more. Structure-activity relationship records seem insufficient, and the studies on nano-combined approaches to improve its soluble property in living bodied medium are needed.

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.

Anti-inflammatory and immunoregulatory effects of icariin and icaritin

Inflammation and immunity dysregulation have received widespread attention in recent years due to their occurrence in the pathophysiology of many conditions. In this regard, several pharmacological studies have been conducted aiming to evaluate the potential anti-inflammatory and immunomodulatory effects of phytochemicals. Epimedium, a traditional Chinese medicine, is often used as a tonic, aphrodisiac, and anti-rheumatic agent. Icariin (ICA) is the main active ingredient of Epimedium and is, once ingested, mainly metabolized into Icaritin (ICT). Data from in vitro and in vivo studies suggested that ICA and its metabolite (ICT) regulated the functions and activation of immune cells, modulated the release of inflammatory factors, and restored aberrant signaling pathways. ICA and ICT were also involved in anti-inflammatory and immune responses in several diseases, including multiple sclerosis, asthma, atherosclerosis, lupus nephritis, inflammatory bowel diseases, rheumatoid arthritis, and cancer. Yet, data showed that ICA and ICT exhibited similar but not identical pharmacokinetic properties. Therefore, based on their higher solubility and bioavailability, as well as trends indicating that single-ingredient compounds offer broader and safer therapeutic capabilities, ICA and ICT delivery systems and treatment represent interesting avenues with promising clinical applications. In this study, we reviewed the anti-inflammatory and immunomodulatory mechanisms, as well as the pharmacokinetic properties of ICA and its metabolite ICT.

Antiosteoporosis Effects, Pharmacokinetics, and Drug Delivery Systems of Icaritin: Advances and Prospects

Osteoporosis is a systemic skeletal disorder affecting over 200 million people worldwide and contributes dramatically to global healthcare costs. Available anti-osteoporotic drug treatments including hormone replacement therapy, anabolic agents, and bisphosphonates often cause adverse events which limit their long-term use. Therefore, the application of natural products has been proposed as an alternative therapy strategy. Icaritin (ICT) is not only an enzyme-hydrolyzed product of icariin but also an intestinal metabolite of eight major flavonoids of the traditional Chinese medicinal plant Epimedium with extensive pharmacological activities, such as strengthening the kidney and reinforcing the bone. ICT displays several therapeutic effects, including osteoporosis prevention, neuroprotection, antitumor, cardiovascular protection, anti-inflammation, and immune-protective effect. ICT inhibits bone resorption activity of osteoclasts and stimulates osteogenic differentiation and maturation of bone marrow stromal progenitor cells and osteoblasts. As for the mechanisms of effect, ICT regulates relative activities of two transcription factors Runx2 and PPARγ, determines the differentiation of MSCs into osteoblasts, increases mRNA expression of OPG, and inhibits mRNA expression of RANKL. Poor water solubility, high lipophilicity, and unfavorable pharmacokinetic properties of ICT restrict its anti-osteoporotic effects, and novel drug delivery systems are explored to overcome intrinsic limitations of ICT. The paper focuses on osteogenic effects and mechanisms, pharmacokinetics and delivery systems of ICT, and highlights bone-targeting strategies to concentrate ICT on the ideal specific site of bone. ICT is a promising potential novel therapeutic agent for osteoporosis.

Icaritin-elevated circ_0000190 suppresses the malignant progression of multiple myeloma by targeting miR-301a

Icaritin has potential anticancer effects on various cancers, including multiple myeloma (MM). Recent studies claim that Icaritin can regulate the expression of noncoding RNAs (ncRNAs) in cancer development. This study aimed to investigate the role of circular RNA_0000190 (circ_0000190) and functional mechanism in Icaritin-treated MM. The expression of circ_0000190 and miR-301a was detected by quantitative real-time polymerase chain reaction. Cell cycle, apoptosis, migration, and invasion were investigated using flow cytometry assay, and transwell assay, respectively. The expression of BAX, BCL2, MMP2, and CCND1 was detected by western blot. The predicted target relationship between circ_0000190 and miR-301a was validated by dual-luciferase reporter assay and RNA immunoprecipitation assay. The activation of JAK1/STAT3 pathway was examined using western blot. Circ_0000190 was strikingly downregulated in MM specimens and cell lines, and Icaritin promoted the expression of circ_0000190. In function, circ_0000190 overexpression promoted MM cell cycle arrest and apoptosis but restrained the ability of migration and invasion. Icaritin blocked the development of MM by increasing circ_0000190 expression. MiR-301a was identified as a target of circ_0000190, and miR-301a reintroduction largely abolished the effects of circ_0000190 overexpression. The activation of JAK1/STAT3 pathway was promoted by miR-301a restoration. Icaritin played anticancer effects in MM partly by enhancing the expression of circ_0000190 and regulating the circ_0000190/miR-301a pathway. This study enhanced the understanding of the mechanism of Icaritin associated with circRNAs in MM.

Rapid intestinal glucuronidation and hepatic glucuronide recycling contributes significantly to the enterohepatic circulation of icaritin and its glucuronides in vivo

Icaritin (ICT), a prenylflavonoid derivative extracted from the Epimedium genus, has exhibited antitumor effects in hepatocellular carcinoma (HCC) cells and safety and tolerance in clinical settings. However, ICT exhibits low blood concentration and the in vivo dominant plasma species of ICT is glucuronides [icaritin-3-glucuronide (G1), icaritin-7-glucuronide (G2) and icaritin-3, 7-diglucuronide (DIG)]. Therefore, how ICT reaches the liver and exerts its effect with low toxicity remains unknown. Therefore, pharmacokinetic experiments (p.o. 5 mg/kg with/out 50 mg/kg inhibitor combo), intestinal perfusion (2 μM ICT), portal vein infusion (1.6 μM ICT, 7.1 μM G1, 6.8 μM G2 and 4.4 μM DIG), and in vitro studies (the concentration range of substrates: 0.3-10 μM) were conducted in the present study. Ultimately, ICT was shown to undergo glucuronidation by the intestine and subsequent uptake by hepatocytes via organic anion transporting peptides (OATPs) as conjugates, followed by biliary excretion mainly as diglucuronide. In conclusion, we found for the first time that the intestine is considered as the major metabolic organ, liver as the main recycling organ for the enterohepatic recycling (EHR) of ICT. Moreover, DIG is the main species in the systemic circulation following oral administration of ICT which explains the low toxicity of ICT in clinical settings.

Pharmacokinetics and metabolism of icaritin in rats by UPLC-MS/MS

Icaritin (ICT) has distinct bioactivities, especially known for its beneficial effects on bone-related degenerative disorders; however, its pharmacokinetic properties remain unknown. A novel developed UPLC-MS/MS method for the determination of ICT and its main metabolite glucuronidated icaritin (GICT) was firstly applied to pharmacokinetic and metabolism studies of ICT in female rats, which were intraperitoneally given 40 mg/kg ICT. Following the protein precipitation of plasma samples with acetonitrile, ICT and GICT were separated on a C18 column using gradient elution mode and quantified in the multiple reaction monitoring mode. The linearities were acceptable for ICT (r = 0.9960) and GICT (r = 0.9968), and the lower limit of quantification values was 0.5 and 5 ng/ml, respectively. The accuracy fell in the range of 92.0%-103.1% and precisions were within 9.5%. Good linearity, accuracy, precision, and recovery were achieved for the UPLC-MS/MS method. ICT was predominantly and rapidly biotransformed to GICT which was slowly eliminated in vivo with a terminal half-life value of 4.51 hr. Pharmacokinetics of pure ICT eliminated biotransformation interference of Epimedium extract and disclosed genuine pharmacokinetic manner of ICT, as well as firstly elucidated low concentration and bioavailability of ICT in rat plasma.

Metabolite Profiling, Pharmacokinetics, and In Vitro Glucuronidation of Icaritin in Rats by Ultra-Performance Liquid Chromatography Coupled with Mass Spectrometry

Icaritin is a naturally bioactive flavonoid with several significant effects. This study aimed to clarify the metabolite profiling, pharmacokinetics, and glucuronidation of icaritin in rats. An ultra-performance liquid chromatography coupled with mass spectrometry (UPLC-MS) assay was developed and validated for qualitative and quantitative analysis of icaritin. Glucuronidation rates were determined by incubating icaritin with uridine diphosphate glucuronic acid- (UDPGA-) supplemented microsomes. Kinetic parameters were derived by appropriate model fitting. A total of 30 metabolites were identified or tentatively characterized in rat biosamples based on retention times and characteristic fragmentations, following proposed metabolic pathway which was summarized. Additionally, the pharmacokinetics parameters were investigated after oral administration of icaritin. Moreover, icaritin glucuronidation in rat liver microsomes was efficient with CL_int (the intrinsic clearance) values of 1.12 and 1.56 mL/min/mg for icaritin-3-O-glucuronide and icaritin-7-O-glucuronide, respectively. Similarly, the CL_int values of icaritin-3-O-glucuronide and icaritin-7-O-glucuronide in rat intestine microsomes (RIM) were 1.45 and 0.86 mL/min/mg, respectively. Taken altogether, dehydrogenation at isopentenyl group and glycosylation and glucuronidation at the aglycone were main biotransformation process in vivo. The general tendency was that icaritin was transformed to glucuronide conjugates to be excreted from rat organism. In conclusion, these results would improve our understanding of metabolic fate of icaritin in vivo.

Oral absorption, distribution, metabolism, and excretion of icaritin in rats by Q-TOF and UHPLC-MS/MS

Icaritin (ICT) displays numerous pharmacological activities for the treatment of various cancers, osteoporosis, inflammation, and angiocardiopathy. The absorption, distribution, metabolism, and excretion of ICT still remain unknown. ICT was administered to rats at 2 mg/kg for intravenous injection or 40 mg/kg for oral route. Major metabolite of ICT was identified using quadrupole time-of-flight (Q-TOF), and ICT and its major metabolite were quantified in plasma, tissues, urine, faeces, and bile by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). A total of 24 metabolites of ICT in plasma were identified and mono C-7 glucuronide glucuronidated icaritin (GICT) was the major metabolite of ICT after oral administration. The absolute bioavailability of ICT was 4.33% although ICT was rapidly absorbed into the blood. For oral administration, concentrations of GICT at various time points was 6.38-8.81-fold higher than those of ICT, and the area under the curve (AUC) of GICT was about 8-fold higher than that of ICT, while AUC values of ICT and GICT were almost equal for intravenous injection. Approximately 65.7% ICT and 42.7% GICT were distributed in liver and kidney, respectively. Unabsorbed ICT was mainly excreted as the parent form in faeces with at least 60% of administered dose during 24 h, whereas absorbed ICT was predominantly excreted as GICT from urine with 2.74% of administered dose accounting for 63.28% of absorbed drug. ICT was rapidly absorbed into the blood although a large amount of ICT remained unabsorbed, and then rapidly and mainly metabolized to GICT. ICT mainly distributed in liver, while GICT predominantly distributed in kidney. Absorbed ICT and GICT were predominantly excreted via urine, and unabsorbed ICT was mainly excreted as the parent form in faeces. Copyright © 2017 John Wiley & Sons, Ltd.

Glucuronidation of icaritin by human liver microsomes, human intestine microsomes and expressed UDP-glucuronosyltransferase enzymes: identification of UGT1A3, 1A9 and 2B7 as the main contributing enzymes

1. Icaritin is a natural flavonoid with anti-osteoporosis activity. This study aimed to characterize icaritin glucuronidation by pooled human liver microsomes (HLM) and pooled human intestine microsomes (HIM), and to determine the contribution of individual UDP-glucuronosyltrans-ferase (UGT) enzyme to icaritin glucuronidation. 2. Glucuronidation rates were determined by incubating icaritin with uridine diphosphate glucuronic acid (UDPGA)-supplemented microsomes. Kinetic parameters were derived by appropriate model fitting. Relative activity factors and activity correlation analysis were performed to identify main UGT isoforms. 3. UGT1A3, 1A7, 1A8, 1A9 and 2B7 were mainly responsible for catalyzing the formation of two glucuronides (G1 and G2). Icaritin 3-O-glucuronidation (G1) was significantly correlated with Chenodeoxycholic acid (CDCA) glucuronidation (r = 0.787, p = 0.002), propofol glucuronidation (r = 0.661, p = 0.019) and Zidovudine (AZT) glucuronidation (r = 0.805, p = 0.002). Similarly, icaritin 7-O-glucuronidation (G2) was also correlated with CDCA glucuronidation (r = 0.640, p = 0.025), propofol glucuronidation (r = 0.592, p = 0.043) and AZT glucuronidation (r = 0.661, p = 0.019). In addition, UGT1A3, 1A9 and 2B7 contributed 37.5, 33.8 and 21.3% for G1 in pooled HLM, respectively. Also, UGT1A3, 1A9 and 2B7 contributed 34.3, 20.0 and 8.6% for G2 in pooled HLM, respectively. 4. Icaritin was subjected to significant glucuronidation, wherein UGT1A3, 1A7, 1A8, 1A9 and 2B7 were main contributing enzymes.

Optimized Biotransformation of Icariin into Icariside II by β-Glucosidase from Trichoderma viride Using Central Composite Design Method

A crude β-glucosidase has been produced from Trichoderma viride and used to explore a simple method to prepare icariside II from icariin. The crude enzyme has been studied by zymography method and used for hydrolysis of ICA. To achieve a high conversion rate of ICA, various factors have been studied including pH, reaction time, temperature, initial concentration of enzyme, and initial concentration of ICA through central composite design experiments. In the condition of the optimum hydrolysis parameters with pH 4.0, 41°C, 1.0 mg/mL ICA, and 9.8 U/mL crude β-glucosidase, the conversion rate of ICA reached 95.03% at 1 h. Moreover, the cytotoxicity test showed that ICA II performed inhibition effects on proliferation of A549 cell, while ICA has no cytotoxicity. It indicated that the hydrolysis transformation study of ICA is valuable for exploration of active new drugs.

Pharmacokinetics and Brain Distribution and Metabolite Identification of Coptisine, a Protoberberine Alkaloid with Therapeutic Potential for CNS Disorders, in Rats

Coptisine (COP), a protoberberine alkaloid (PBA) from Chinese medicinal plants (such as family Berberidaceae), may be useful for improving central nervous system disorders. However, its pharmacokinetics, disposition and metabolism are not well defined. In the present study, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was established for the analysis of COP in biological samples. To better understand its in vivo pharmacological activities, COP concentrations in rat plasma were determined after oral (50 mg/kg) and intravenous administration (10 mg/kg). For the brain distribution study, the concentration of COP in five different regions was examined after intravenous administration at 10 mg/kg. Pharmacokinetic parameters from the COP concentration-time profiles in plasma and brain, and the brain-to-plasma coefficient (Kp, brain) were calculated by non-compartmental analysis. The metabolites of COP in rats in vivo and in vitro (urine, bile, liver microsomes and intestinal bacteria incubation) were also identified. Seventeen metabolites, including 11 unconjugated metabolites formed by hydroxylation, hydrogenation, demethylation, dehydrogenation, demethylation, and 6 glucuronide and sulfate conjugates were identified for the first time. The results suggested that COP had low oral bioavailability of 8.9% and a short (plasma) half-life (T1/2=0.71 h) in rats. After intravenous administration, it quickly crossed the blood-brain barrier, accumulating at higher concentrations and then was slowly eliminated from different brain regions. Moreover, COP was transformed into metabolites through multiple metabolic pathways in vivo and in vitro. These results should help to promote further research on COP and contribute to clarifying the metabolic pathways of PBAs.

Pharmacological effects and pharmacokinetic properties of icariin, the major bioactive component in Herba Epimedii

Herba Epimedii is an important medicinal plant which has been used in various traditional Chinese formulations for thousands of years as well as in modern proprietary traditional Chinese medicine products. It has extensive clinical indications, especially for the treatment of sexual dysfunction and osteoporosis. There have been more than 260 chemical moieties identified in the genus Epimedium most of which belong to flavonoids. Icariin is the most abundant constituent in Herba Epimedii. Icariin is pharmacologically bioactive and demonstrates extensive therapeutic capacities such as osteoprotective effect, neuroprotective effect, cardiovascular protective effect, anti-cancer effect, anti-inflammation effect, immunoprotective effect and reproductive function. Particularly, the significant osteogenic effect of icariin made it a promising drug candidate in bone tissue engineering. The current review paper aims to summarize the literatures reporting the pharmacological effects of icariin. The pharmacokinetic properties of bioactive ingredients in Herba Epimedii have also been discussed.

The antiosteoporotic activity of central-icaritin (CIT) on bone metabolism of ovariectomized rats

Central-icaritin (CIT) is a flavonoid aglycone first discovered in our laboratory, which is an isomeric aglycone of icaritin (IT). We wanted to know whether CIT also had anti-osteoporosis activity. In this study, CIT was investigated in an ovariectomized rat (OVX) model. Fifty-six 6-month old female Sprague-Dawley rats were randomly assigned to sham operated group (Sham) and six OVX subgroups (n = 8 each). The OVX rats were then subdivided into six groups treated with vehicle (OVX), icaritin (IT, 40 mg/kg body weight/day), estradiol valerate (EV, 100 μg/kg body weight/day) or CIT (10, 20, and 40 mg/kg body weight/day) for 12 weeks, respectively. Then, the serum biochemical parameters, bone mineral density (BMD), bone biomechanical properties, bone microarchitecture, bone immunohistochemistry and related protein and gene expressions were evaluated. In OVX rats, the increases of body weight, HOP, AKP, and TRACP5b levels, and the decreases of uterus wet weight, femurs weight, BMD, serum OPG/RANKL and OCN were significantly inhibited by CIT treatment. Micro-CT analysis results showed that CIT apparently enhanced trabecular bone compared with the OVX group (p < 0.05). Total femur BMD and biomechanical strength of tibia were significantly improved (p < 0.05) after 12 weeks of CIT administration. In addition, the CIT administration also significantly enhanced the OPG expression, whereas reduced the RANKL expression in femurs according to RT-PCR, western blot assays and immunohistochemical evaluation. CIT had the antiosteoporotic activity, and its antiosteoporotic effects in OVX rats may be stronger than that of IT.

Biodistribution evaluation of icaritin in rats by ultra-performance liquid chromatography-tandem mass spectrometry

ETHNOPHARMACOLOGICAL RELEVANCE

Icaritin (ICT) is a major bioactive prenylflavonoid derivative contained in the Epimedium which is a widely used herbal medicine for the treatment of infertility, impotence, cardiovascular and skeletal diseases listed in the Chinese Pharmacopoeia. The aim of this study is to investigate the tissue distribution of ICT in rats by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) MATERIALS AND METHODS: ICT was intraperitoneally administrated to rats for 7 consecutive days at dose levels of 20, 40 and 60 mg/kg/day, respectively. Various tissue homogenates were pretreated by protein precipitation with acetonitrile. ICT and internal standard coumestrol were separated on a BEH C18 column with a gradient mobile phase and detected using precursor-product ion transitions of m/z 367.1→297.1 for ICT and 267.0→211.1 for coumestrol at the negative ionization mode, respectively.

RESULTS

ICT was widely distributed in rat's various tissues and its concentrations in tissues increased with elevated doses. A sensitive and reliable UPLC-MS/MS method was firstly established to quantify ICT in rat tissues. The lower limit of quantification was 0.5 ng/mL based on 100 μL of tissue homogenates. The intra- and inter-day accuracy at all levels fell in the ranges of 90.8-103.4% and 91.6-100.3%, and the intra- and inter-day precision (RSD) were in the ranges of 2.9-10.5% and 2.6-9.1%, respectively.

CONCLUSIONS

The UPLC-MS/MS showed good accuracy, precision and recovery and was suitable for the quantification of ICT in rat tissues. Wide distribution of ICT could helpfully elucidate systemic effects and various functions of ICT.

Metabolic profiling of isomeric aglycones central-icaritin (c-IT) and icaritin (IT) in osteoporotic rats by UPLC-QTOF-MS

The isomers, although of similarly chemical structures, have different pharmacological activities due to their metabolic processes in vivo. Central-icaritin (c-IT) and icaritin (IT) are isomers and major bioactive aglycones of the Herba Epimedii. In this study, we found that the anti-osteoporotic effect of c-IT was stronger than IT on bone structural changes in osteoporotic rats evaluated by Micro-μCT with the parameters of bone mineral density (BMD), bone mineral content (BMC), tissue mineral content (TMC), and tissue mineral density (TMD). c-IT treatment significantly increased the bone microarchitecture, compared with IT (p < 0.05). In order to explain their differences in anti-osteoporosis, the metabolic profiling and pathways of c-IT and IT in the plasma, bile, urine, and faeces of ovariectomized (OVX) rats were investigated by ultra-performance liquid chromatography quadrupole time of flight mass spectrometry (UPLC-QTOF-MS) after oral administration of c-IT or IT (80 mg/kg). Finally, 59 metabolites of c-IT and 43 metabolites of IT were identified by elucidating their corresponding quasimolecular ions and fragment ions. IT could be quickly absorbed into blood and reached a maximum plasma concentration, and then be rapidly conversed to its glucuronidation metabolites, most of which were excreted out by urine. Interestingly, the absorbed and conjugated speeds of c-IT were slower than IT. The metabolic processes of c-IT existed enterohepatic circulation, which decreased the metabolism and excretion rate of c-IT, and prolonged the anti-osteoporosis effect. Our findings provided evidence on the difference on metabolic profiles of c-IT and IT in osteoporotic rats, which might shed new lights on improving anti-osteoporotic effects of IT and c-IT.

A comparative study on the metabolism of Epimedium koreanum Nakai-prenylated flavonoids in rats by an intestinal enzyme (lactase phlorizin hydrolase) and intestinal flora

The aim of this study was to compare the significance of the intestinal hydrolysis of prenylated flavonoids in Herba Epimedii by an intestinal enzyme and flora. Flavonoids were incubated at 37 °C with rat intestinal enzyme and intestinal flora. HPLC-UV was used to calculate the metabolic rates of the parent drug in the incubation and LC/MS/MS was used to determine the chemical structures of metabolites generated by different flavonoid glycosides. Rates of flavonoid metabolism by rat intestinal enzyme were quicker than those of intestinal flora. The sequence of intestinal flora metabolic rates was icariin > epimedin B > epimedin A > epimedin C > baohuoside I, whereas the order of intestinal enzyme metabolic rates was icariin > epimedin A > epimedin C > epimedin B > baohuoside I. Meanwhile, the LC/MS/MS graphs showed that icariin produced three products, epimedin A/B/C had four and baohuoside I yielded one product in incubations of both intestinal enzyme and flora, which were more than the results of HPLC-UV due to the fact LC/MS/MS has lower detectability and higher sensitivity. Moreover, the outcomes indicated that the rate of metabolization of flavonoids by intestinal enzyme were faster than those of intestinal flora, which was consistent with the HPLC-UV results. In conclusion, the metabolic pathways of the same components by intestinal flora and enzyme were the same. What’s more, an intestinal enzyme such as lactase phlorizin hydrolase exhibited a more significant metabolic role in prenylated flavonoids of Herba Epimedi compared with intestinal flora.

A strategy for the improvement of the bioavailability and antiosteoporosis activity of BCS IV flavonoid glycosides through the formulation of their lipophilic aglycone into nanocrystals

Epimedium-derived flavonoid glycosides are widely used for the prevention of osteoporosis, but these compounds generally exhibit poor membrane permeability and oral absorption. To address these limitations, the bioactive lipophilic aglycone icaritin (ICT) was selected and successfully developed into nanocrystals (ICTN) through the antisolvent-precipitation method. After the parameters in the preparation of ICTN were optimized, the morphology, crystallinity, adsorption of the stabilizers on the ICT surface, and the dissolution of the resulting nanocrystals were characterized. The pharmacokinetics in rat and the in vitro antiosteoporosis activity of serum withdrawn after the oral administration of ICTN to rats on mouse osteoblastic cells were evaluated. Consistent with its good performance in stabilizing the ICT nanosuspension, atomic force microscopy showed that hydroxypropyl methylcellulose (HPMC) exhibits better adsorption on the ICT surface compared with other stabilizers. Needle-shaped crystals (∼ 220 nm in diameter) with a high drug loading (∼ 90%) were generated when 0.16 mL of the ICT acetone solution (10 mg/mL) was injected quickly into 2 mL of the HPMC solution (0.02%, w/w) under ultrasonication for 10 s at room temperature. The thermal analysis demonstrated that the majority of the particles are in their crystalline forms, similarly to the unformulated ICT. After oral administration, ICTN exhibited a faster dissolution rate and significantly faster absorption, as supported by the increased AUC0-36h and Cmax and the reduced Tmax of these nanocrystals compared with the raw suspension (p < 0.05). Compared with blank serum, enhanced proliferation and differentiation activities were observed when serum withdrawn after the oral administration of ICTN in rat was incubated with osteoblast MC3T3-E1 cells. The present delivery system could provide a new promising strategy for BCS IV glycoside of flavonoids or other natural products by formulation of their bioactive lipophilic aglycone forms to enhance oral absorption and in vivo bioactivity.