Amino Acid Carbamates As Prodrugs Of Resveratrol

Synthesis, Cytotoxicity, and Mechanistic Evaluation of Tetrahydrocurcumin-Amino Acid Conjugates as LAT1-Targeting Anticancer Agents in C6 Glioma Cells

Glioblastoma, a fatal brain cancer with limited treatments and poor prognosis, could benefit from targeting the L-type amino acid transporter I (LAT1). LAT1 is essential for cancer cells to acquire necessary amino acids. Tetrahydrocurcumin (THC), a key curcumin derivative, shows potential for glioblastoma treatment. However, its effectiveness is hindered by poor physicochemical and pharmacokinetic properties. Therefore, this study aims to improve the therapeutic efficacy of THC against glioblastoma by chemically modifying it to target LAT1. A novel series of THC-amino acid conjugates were synthesized by conjugating five amino acids: glycine, leucine, isoleucine, and phenylalanine to THC via carbamate bonds. The therapeutic efficacy of THC-amino acid conjugates was further examined in C6 glioma cells, including the role of LAT1 in their therapeutic effects. Among the conjugates tested, THC conjugated with two phenylalanines (THC-di-Phe) showed remarkably higher cytotoxicity against C6 glioma cells (35.8 μM) compared to THC alone (110.7 μM). THC-di-Phe induced cellular death via necrosis and apoptosis, outperforming THC. Additionally, THC-di-Phe inhibited C6 cell proliferation and migration more effectively than THC. Co-incubation of THC-di-Phe with the LAT1 inhibitor 2-Aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH) further increased cellular death. THC-di-Phe also significantly inhibited the P70SK/S6 pathway, regulated by LAT1 inhibitors, more effectively than THC and displayed a similar binding mode with both JX-075 and BCH to the active site of LAT1. Findings suggest the potential role of THC-di-Phe as a LAT1 inhibitor and provide novel insight into its use as a potent antitumor agent in glioma with increased therapeutic efficacy.

Improving oral absorption of a rapidly crystallizing parent drug using prodrug strategy: Comparison of phosphate versus glycine based prodrugs

With an increasing number of Biopharmaceutical Classification System (BCS) II/IV pipeline compounds, solubilizing and supersaturating formulation strategies are becoming prevalent. Beyond formulation and solid form strategies, prodrugs are also employed to overcome solubility-limited absorption of poorly water-soluble compounds. Prodrugs can potentially yield supersaturated systems upon conversion to the parent drug intraluminally and thus enhance absorption. However, supersaturation also increases the driving force for crystallization, resulting in low solution concentrations, which can potentially negate the advantage of prodrugs. In this work, two unique solubility-enhancing prodrugs, phosphate and glycine esters, were investigated for a rapidly crystallizing parent drug. Ex vivo absorption studies using rat tissue and in vivo studies in dogs were performed. Conversion rate of the phosphate prodrug to the parent was dependent on the milieu and increased ∼24-fold in the presence of intestinal contents as medium and tissue relative to neat buffer. In contrast, conversion of the glycine prodrug was minimal under any conditions tested, suggesting that the conversion occurs after absorption into the enterocytes. Phosphate prodrug showed a non-linear increase in parent drug absorptive flux across rat intestinal tissue with concentration when intestinal contents were used as donor media. This was attributed to rapid conversion and high supersaturation of the parent drug which subsequently resulted in crystallization at high doses in the donor chamber. Glycine prodrug did not undergo complete conversion at high doses and was absorbed unchanged on the basolateral side, indicating saturation of the converting enzymes in the enterocytes. The combined flux (parent drug and glycine) showed a linear increase with dose and crystallization was not observed. Under physiological conditions, glycine prodrug that is absorbed unchanged from the intestine can potentially undergo complete conversion in hepatocytes after absorption and make the parent drug systemically available. Thus, glycine prodrug provided overall higher absorption compared to phosphate prodrug. The observed flux levels for both the prodrugs were higher compared to the parent drug alone, highlighting an advantage to use of a prodrug strategy to improve absorption of such compounds. Oral dosing in a dog PK study revealed that the bioavailability using the phosphate prodrug was ∼50% whereas, it was ∼100% with glycine prodrug, supporting the in vitro observations.

Synthesis and biological evaluation of the novel chrysin prodrug for non-alcoholic fatty liver disease treatment

Background: Chrysin (5,7-dihydroxyflavone) is a natural flavonoid that has been reported as a potential treatment for non-alcoholic fatty liver disease (NAFLD). However, extensive phase II metabolism and poor aqueous solubility led to a decrease in the chrysin concentration in the blood after oral administration, limiting its pharmacological development in vivo. Methods: In the present study, we synthesized a novel chrysin derivative prodrug (C-1) to address this issue. We introduced a hydrophilic prodrug group at the 7-position hydroxyl group, which is prone to phase II metabolism, to improve water solubility and mask the metabolic site. Further, we evaluated the ameliorative effects of C-1 on NAFLD in vitro and in vivo by NAFLD model cells and db/db mice. Results: In vitro studies indicated that C-1 has the ability to ameliorate lipid accumulation, cellular damage, and oxidative stress in NAFLD model cells. In vivo experiments showed that oral administration of C-1 at a high dose (69.3 mg/kg) effectively ameliorated hyperlipidemia and liver injury and reduced body weight and liver weight in db/db mice, in addition to alleviating insulin resistance. Proteomic analysis showed that C-1 altered the protein expression profile in the liver and particularly improved the expression of proteins associated with catabolism and metabolism. Furthermore, in our preliminary pharmacokinetic study, C-1 showed favorable pharmacokinetic properties and significantly improved the oral bioavailability of chrysin. Conclusion: Our data demonstrated that C-1 may be a promising agent for NAFLD therapy.

Natural Amino Acid-Bearing Carbamate Prodrugs of Daidzein Increase Water Solubility and Improve Phase II Metabolic Stability for Enhanced Oral Bioavailability

Daidzein (DAN) is an isoflavone, and it is often found in its natural form in soybean and food supplements. DAN has poor bioavailability owing to its extremely low water solubility and first-pass metabolism. Herein, we hypothesized that a bioactivatable natural amino acid-bearing carbamate prodrug strategy could increase the water solubility and metabolic stability of DAN. To test our hypothesis, nine amino acid prodrugs of DAN were designed and synthesized. Compared with DAN, the optimal prodrug (daidzein-4'-O-CO-N-isoleucine, D-4'-I) demonstrated enhanced water solubility and improved phase II metabolic stability and activation to DAN in plasma. In addition, unlike the passive transport of DAN, D-4'-I maintained high permeability via organic anion-transporting polypeptide 2B1 (OATP2B1)-mediated transport. Importantly, D-4'-I increased the oral bioavailability by 15.5-fold, reduced the gender difference, and extended the linear absorption capacity in the pharmacokinetics of DAN in rats. Furthermore, D-4'-I exhibited dose-dependent protection against liver injury. Thus, the natural amino acid-bearing carbamate prodrug strategy shows potential in increasing water solubility and improving phase II metabolic stability to enhance the oral bioavailability of DAN.

Molecular Masking of Synthetic Immunomodulator Evokes Antitumor Immunity With Reduced Immune Tolerance and Systemic Toxicity by Temporal Activity Recovery and Sustained Stimulation

Activation of the innate immune system counteracts tumor-induced immunosuppression. Hence, small molecule-based toll-like receptor 7/8 agonists (TLR7/8a), which can modulate immunosuppression in the tumor microenvironment along with the activation of innate immunity, are emerging as essential components of cancer immunotherapy. However, the clinical application of synthetic TLR7/8a therapies is limited by systemic immune-associated toxicity and immune tolerance induced by uncontrolled stimulatory activities and repeated treatments. To address these limitations, a dynamic immunomodulation strategy incorporating masking and temporal recovery of the activity of TLR7/8a through prodrug-like TLR7/8a (pro-TLR7/8a) at the molecular level and a sustained and controlled release of active TLR7/8a from nanoliposome (pro-TLR7/8a) (NL(pro-TLR7/8)) in a macroscale depot are designed. Immunization with cationic NL(pro-TLR7/8) and anionic antigens triggers robust activation of innate immune cells as well as antigen-specific T cell responses, eliciting reprogramming of immunosuppressive cells into tumor-suppressive cells, with decreased systemic adverse effects and immune tolerance. Combination treatment with NL(pro-TLR7/8a) and immune checkpoint inhibitors (anti-CTLA-4 plus anti-PD-L1) or nanoliposomes (Doxorubicin) has synergistic effects on antitumor immunity in various tumor models. The concept of pro-TLR7/8a suggested herein may facilitate the advancement of small-molecule-based immunomodulators for clinical translation and safe and effective cancer immunotherapy.

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.

Research advances in peptide‒drug conjugates

Peptide‒drug conjugates (PDCs) are drug delivery systems consisting of a drug covalently coupled to a multifunctional peptide via a cleavable linker. As an emerging prodrug strategy, PDCs not only preserve the function and bioactivity of the peptides but also release the drugs responsively with the cleavable property of the linkers. Given the ability to significantly improve the circulation stability and targeting of drugs in vivo and reduce the toxic side effects of drugs, PDCs have already been extensively applied in drug delivery. Herein, we review the types and mechanisms of peptides, linkers and drugs used to construct PDCs, and summarize the clinical applications and challenges of PDC drugs.

Habb-e-Asgandh Suppresses Cell Proliferation and Induces Apoptosis through Mitochondria Dysfunction in Multiple Myeloma Cells (RPMI8226)

OBJECTIVE

This study was conducted to assess the anti-neoplastic properties of Habb-e-Asgandh in multiple myeloma cells (RPMI8226).

METHODS

Multiple myeloma cells (RPMI8226) were cultured according to the ATCC's instruction. The anti-proliferative effect of HeA was assessed by MTT assay and proliferating cellnuclear antigen (PCNA) activity. Cell cycle analysis, cellular apoptosis, and mitochondria membrane potential analysis was done by flow cytometry. Total antioxidants, migratory potential, angiogenesis and inflammatory biomarkers were also estimated after treatment of RPMI8226 with HeA.

RESULTS

LD30 and LD50 dose of HeA was 0.3mg/ml and 0.5mg/ml respectively determined by MTT assay and also confirmed by a reduced PCNA activity. Cell cycle analysis of RPMI8226 cells revealed that sub-G0/G1 phase increases upon treatment with HeA alone or in combination with lenalidomide. Annexin V-FITC/PI is used to detect early apoptosis, late apoptosis and necrotic cells and results showed that percentage of apoptotic cells increased in RPMI8226 cells after treatment with HeA. Also, HeA induces loss of mitochondria membrane potential (MMP) in MM cells in-vitro as measured by cationic JC1 dye staining. Upon treatment, the abnormal overexpression of oncogenic protein, AKT serine/threonine kinase has also been reduced. Furthermore, anti-oxidants level also increased while migratory potential, angiogenesis and inflammation decreased in multiple myeloma cell line upon treatment with HeA.

CONCLUSION

Collectively, our results demonstrated that integrative therapy of habb-e-asgandh efficiently eliminates the need to use higher dose of lenalidomide for multiple myeloma treatment.

Chinese medicinal herbs as potential prodrugs for obesity

Obesity is a leading worldwide health threat with ever-growing prevalence, it promotes the incidence of various diseases, particularly cardiovascular disease, metabolic syndrome, diabetes, hypertension, and certain cancers. Traditional Chinese Medicine (TCM) has been used to control body weight and treat obesity for thousands of years, Chinese medicinal herbs provide a rich natural source of effective agents against obesity. However, some problems such as complex active ingredients, poor quality control, and unclear therapeutic mechanisms still need to be investigated and resolved. Prodrugs provide a path forward to overcome TCM deficiencies such as absorption, distribution, metabolism, excretion (ADME) properties, and toxicity. This article aimed to review the possible prodrugs from various medicinal plants that demonstrate beneficial effects on obesity and seek to offer insights on prodrug design as well as a solution to the global obesity issues.

Recent advance on carbamate-based cholinesterase inhibitors as potential multifunctional agents against Alzheimer's disease

Alzheimer's disease (AD), as the fourth leading cause of death among the elderly worldwide, has brought enormous challenge to the society. Due to its extremely complex pathogeneses, the development of multi-target directed ligands (MTDLs) becomes the major strategy for combating AD. Carbamate moiety, as an essential building block in the development of MTDLs, exhibits structural similarity to neurotransmitter acetylcholine (ACh) and has piqued extensive attention in discovering multifunctional cholinesterase inhibitors. To date, numerous preclinical studies demonstrate that carbamate-based cholinesterase inhibitors can prominently increase the level of ACh and improve cognition impairments and behavioral deficits, providing a privileged strategy for the treatment of AD. Based on the recent research focus on the novel cholinesterase inhibitors with multiple biofunctions, this review aims at summarizing and discussing the most recent studies excavating the potential carbamate-based MTDLs with cholinesterase inhibition efficacy, to accelerate the pace of pleiotropic cholinesterase inhibitors for coping AD.

Physicochemical investigation of a novel curcumin diethyl γ-aminobutyrate, a carbamate ester prodrug of curcumin with enhanced anti-neuroinflammatory activity

Curcumin is a polyphenol compound that alleviates several neuroinflammation-related diseases including Alzheimer's disease, Parkinson's disease, multiple sclerosis, epilepsy and cerebral injury. However, the therapeutic efficacy of curcumin is limited by its poor physicochemical properties. The present study aimed to develop a new carrier-linked curcumin prodrug, curcumin diethyl γ-aminobutyrate (CUR-2GE), with improved physicochemical and anti-neuroinflammatory properties. CUR-2GE was designed and synthesized by conjugating curcumin with gamma-aminobutyric acid ethyl ester (GE) via a carbamate linkage. The carbamate linkage was selected to increase stability at acidic pH while GE served as a promoiety for lipophilic enhancement. The synthesized CUR-2GE was investigated for solubility, partition coefficient, stability, and bioconversion. The solubility of CUR-2GE was less than 0.05 μg/mL similar to that of curcumin, while the lipophilicity with log P of 3.57 was significantly increased. CUR-2GE was resistant to chemical hydrolysis at acidic pH (pH 1.2 and 4.5) as anticipated but rapidly hydrolyzed at pH 6.8 and 7.4. The incomplete hydrolysis of CUR-2GE was observed in simulated gastrointestinal fluids which liberated the intermediate curcumin monoethyl γ-aminobutyric acid (CUR-1GE) and the parent curcumin. In plasma, CUR-2GE was sequentially converted to CUR-1GE and curcumin within 1 h. In lipopolysaccharide (LPS)-stimulated BV-2 microglial cells, CUR-2GE effectively attenuated the pro-inflammatory mediators by decreasing the secretion of nitric oxide and cytokines (TNF-α and IL-6) to a greater extent than curcumin due to an increase in cellular uptake. Altogether, the newly developed acid-stable CUR-2GE prodrug is a potential pre-clinical and clinical candidate for further evaluation on neuroprotective and anti-neuroinflammatory effects.

Synthesis and Biochemical Evaluation of Baicalein Prodrugs

Baicalein (5,6,7-trihydroxy-2-phenyl-4H-1-benzopyran-4-one), a flavonoid analog from Scutellaria baicalensis, possesses several pharmacological activities including antioxidant, antiproliferative, and anti-inflammatory activities. We previously reported that baicalein inhibits the thymic stromal lymphopoietin (TSLP)/TSLP receptor (TSLPR) signaling pathways and can be used as an active ingredient in the treatment of asthma and atopic dermatitis. However, baicalein is rapidly metabolized to baicalin and baicalein-6-O-glucuronide in vivo, which limits its preclinical and clinical use. In this study, we designed, synthesized, and evaluated baicalein prodrugs that protect the OH group at the 7-position of the A ring in baicalein with the amino acid carbamate functional group. Comprehensive in vitro and in vivo studies identified compound 2 as a baicalein prodrug candidate that improved the plasma exposure of baicalein in mouse animal studies. Our results demonstrated that this prodrug approach could be further adopted to discover oral baicalein prodrugs.

Dual Strategy for Improving the Oral Bioavailability of Resveratrol: Enhancing Water Solubility and Inhibiting Glucuronidation

Resveratrol (RES) suffers from poor water solubility and extensive metabolism, which lead to low bioavailability. A phospholipid complex (PC) containing RES and a UDP-glucuronosyltransferase (UGT) inhibitor was prepared to address these two limiting factors, thereby improving RES bioavailability. First, 11 natural active ingredients metabolized by similar enzyme subtypes to RES were screened in a glucuronidation assay in liver microsomes. Then, glycyrrhetinic acid (GA), the strongest inhibitor, was prepared with RES in a PC. RES-PC was prepared as a control. As expected, the water solubility and the cumulative dissolution of RES were significantly enhanced by RES-PC and RES/GA-PC. Compared with the RES group, the AUC_0-10 of RES and resveratrol-3-glucuronide (R-3-G) in the RES/GA-PC group showed increases of 2.49- and 1.70-fold, respectively, with the proportion of RES absorption to total absorption increasing 1.45 times. These results demonstrated that RES/GA-PC could improve the bioavailability of RES by increasing its water solubility and inhibiting its glucuronidation.

Synthesis, pharmacological profile and 2D-QSAR studies of curcumin-amino acid conjugates as potential drug candidates

A series of curcumin bis-conjugates 3a-q, 5a-k and 6a-k were synthesized in good yields utilizing an optimized reaction condition. We explored the effect of different amino acids and protecting groups on biological activities of curcumin. The conjugates were screened for anti-inflammatory, analgesic and antimicrobial properties. Some of the conjugates showed promising biological observations with a potency comparable with the standard references. The variations in biological properties concerning different amino acids and protecting groups are interesting observations. Effects of the synthesized conjugates on splenocytes and the production of nitric oxide by lipopolysaccharide-stimulated peritoneal macrophages are correlated with the observed anti-inflammatory properties. We have also established the safety profile of the most active conjugates. Robust 2D-QSAR studies supported and validated biological data.

Neuroprotection by trans-resveratrol against collagenase-induced neurological and neurobehavioural deficits in rats involves adenosine A1 receptors

Objective: Trans-resveratrol has been shown to have neuroprotective effects and could be a promising therapeutic agent in the treatment of intracerebral haemorrhage (ICH). This study aimed to investigate the involvement of the adenosine A1 receptor (A1R) in trans-resveratrol-induced neuroprotection in rats with collagenase-induced ICH.Methods: Sixty male Sprague-Dawley rats weighing 330-380 g were randomly divided into five groups (n = 12): (i) control, (ii) sham-operated rats, (iii) ICH rats pretreated with vehicle (0.1% DMSO saline, i.c.v.), (iv) ICH rats pretreated with trans-resveratrol (0.9 µg, i.c.v.) and (v) ICH rats pretreated with trans-resveratrol (0.9 µg) and the A1R antagonist, DPCPX (2.5 µg, i.c.v.). Thirty minutes after pretreatment, ICH was induced by intrastriatal injection of collagenase (0.04 U). Forty-eight hours after ICH, the rats were assessed using a variety of neurobehavioural tests. Subsequently, rats were sacrificed and brains were subjected to gross morphological examination of the haematoma area and histological examination of the damaged area.Results: Severe neurobehavioural deficits and haematoma with diffuse oedema were observed after intrastriatal collagenase injection. Pretreatment with trans-resveratrol partially restored general locomotor activity, muscle strength and coordination, which was accompanied with reduction of haematoma volume by 73.22% (P < 0.05) and damaged area by 60.77% (P < 0.05) in comparison to the vehicle-pretreated ICH group. The trans-resveratrol-induced improvement in neurobehavioural outcomes and morphological features of brain tissues was inhibited by DPCPX pretreatment.Conclusion: This study demonstrates that the A1R activation is possibly the mechanism underlying the trans-resveratrol-induced neurological and neurobehavioural protection in rats with ICH.

Synthesis and cytotoxic activity of 7,4’-O-modified genistein amino acid derivatives

Fifteen 7,4’- O-modified genistein amino acid derivatives are synthesized through nucleophilic substitution and hydrolysis, followed by condensation with diverse amino acid esters. The antiproliferative activity of all the synthesized compounds is evaluated against three cancer cell lines (MGC-803, HeLa, HCT-116) and one normal cell line (HUVEC) using 5-fluorouracil (5-Fu) as the positive control. The results show that methyl [2-({5-hydroxy-3-[4-(2-{[3-(4-hydroxyphenyl)-1-methoxy-1-oxopropan-2-yl]amino}-2-oxoethoxy)phenyl]-4-oxo-4 H-chromen-7-yl}oxy)acetyl] tyrosinate exhibits significant antiproliferative activity against the MGC-803 cell line with an IC50 value of 8.52 µM, and its inhibitory effects on HeLa and HCT-116 cancer cells are stronger than that of the positive control drug 5-Fu.

Resveratrol cytotoxicity is energy-dependent

Resveratrol is a phytochemical that may promote health. However, it has also been reported to be a toxic compound. The molecular mechanism by which resveratrol acts remains unclear. The inhibition of the oxidative phosphorylation (OXPHOS) pathway appears to be the molecular mechanism of resveratrol. Taking this into account, we propose that the cytotoxic properties of resveratrol depend on the energy (e.g., carbohydrates, lipids, and proteins) availability in the cells. In this regard, in a condition with low energy accessibility, resveratrol could enhance ATP starvation to lethal levels. In contrast, when cells are supplemented with high quantities of energy and resveratrol, the inhibition of OXPHOS might produce a low-energy environment, mimicking the beneficial effects of caloric restriction. This review suggests that investigating a possible complex relationship between caloric intake and the differential effects of resveratrol on OXPHOS may be justified. PRACTICAL APPLICATIONS: A low-calorie diet accompanied by significant levels of resveratrol might modify cellular bioenergetics, which could impact cellular viability and enhance the anti-cancer properties of resveratrol.

Strategies to Improve Resveratrol Systemic and Topical Bioavailability: An Update

In recent years, a great deal of attention has been paid to natural compounds due to their many biological effects. Polyphenols are a class of plant derivatives that have been widely investigated for preventing and treating many oxidative stress-related pathological conditions, such as neurodegenerative and cardiovascular diseases, cancer, diabetes mellitus and inflammation. Among these polyphenols, resveratrol (RSV) has attracted considerable interest owing to its high antioxidant and free radical scavenging activities. However, the poor water solubility and rapid metabolism of RSV lead to low bioavailability, thus limiting its clinical efficacy. After discussing the main biochemical mechanisms involved in RSV biological activities, this review will focus on the strategies attempted to improve RSV effectiveness, both for systemic and for topical administration. In particular, technological approaches involving RSV incorporation into different delivery systems such as liposomes, polymeric and lipid nanoparticles, microemulsions and cyclodextrins will be illustrated, highlighting their potential clinical applications. In addition, chemical modifications of this antioxidant aimed at improving its physicochemical properties will be described along with the results of in vitro and in vivo studies.

The Design, Synthesis, and Characterization of Resveratrol Derivatives Modified by Different γ-Aminobutyric Acid Esters

A novel series of resveratrol modified by γ-aminobutyric acid esters were designed and synthesized. Then, the products were characterized by 1H-NMR, 13C-NMR, and MS, and the melting point was determined. Molecular water solubility, polar surface area, and octanol-water partition were calculated, which correlated well with molecular transport through membranes and, therefore, enabled prediction of transport properties of drugs.

A critical review on grape polyphenols for neuroprotection: Strategies to enhance bioefficacy

The aging of populations worldwide is driving greater demands for dietary polyphenols which have been recognized as promising prophylactic and/or therapeutic agents in the context of neurodegeneration, and are ubiquitously present in plant-based diets. In particular, grape-derived products encompass a wide array of phenolic compounds purported with multiple health benefits including neuroprotective efficacy. Despite the increasing preclinical and clinical evidence demonstrating high potential of grape polyphenol (GPP)-rich botanicals in preventing and attenuating diverse neurodegenerative disorders, the limited bioavailability of GPPs, especially in the brain, generates questions as to their applications and effectiveness in neuroprotection. To address this issue, significant research efforts have been made to enhance oral bioavailability of GPPs via application of novel strategies. This review highlights some critical issues related to the bioavailability and neuroprotective efficacy of GPPs and GPP-rich botanicals. The representative bioavailability-enhancing strategies are critically reviewed to provide practical solutions for augmenting the bioefficacy of GPP-rich botanicals. Synergistic applications of encapsulation techniques (for physiochemical protection and bypassing xenobiotic metabolism) and dietary intervention strategies involving modulation of gut microbiota (for generating more bioavailable phenolic metabolites) appear promising, and may substantially enhance the bioefficacy, especially the neuroprotective efficacy, of orally consumed GPPs.

Combined effects of resveratrol and radiation in GH3 and TtT/GF pituitary adenoma cells

OBJECTIVE

Resveratrol and radiation decrease viability in various tumor cells. This study aims to investigate combined effects of resveratrol and radiation on viability, induction of apoptosis and necrosis, and expression of apoptosis modulators in rodent GH3 and TtT/GF pituitary adenoma cells in vitro.

METHODS

Cells were incubated with 10-100 µM resveratrol. Medium and medium with ethanol served as controls. After 2 h, cells were irradiated with 0-5 Gray (Gy) and further incubated for 48-72 h. Cell viability was quantified using a hemocytometer. Cell death was assessed with an enzyme-linked immunosorbent assay (ELISA) that detects free nucleosomes in cell lysates and free nucleosomes released to the culture medium. Expression of B-cell lymphoma-2 protein (BCL-2) and BCL-2 associated Xprotein (BAX) was measured using quantitative real time-polymerase chain reaction (qRT-PCR) to analyze changes in BAX/BCL-2 ratio.

RESULTS

Resveratrol and irradiation with 4 Gy alone and in combination significantly decreased cell viability (p = 0.017 and less). In the ELISA, 10 μM resveratrol significantly induced apoptosis in TtT/GF cells at 0 Gy (p < 0.001), but not at 3 or 5 Gy. In the ELISA, 10 μM resveratrol significantly induced necrosis in GH3 cells at 0, 3 and 5 Gy (p < 0.001). While qRT-PCR did not demonstrate a significant effect of 10 µM resveratrol or radiation on expression of BAX or BCL-2, a significant increase in the BAX/BCL-2 ratio was found after irradiation with 5 Gy in GH3 cells (p = 0.0027).

CONCLUSION

While moderate irradiation solely led to inhibited proliferation, resveratrol induced cell death in rodent pituitary adenoma cells.

Biopharmaceutical Characterization and Oral Efficacy of a New Rapid Acting Antidepressant Ro 25-6981

Ro 25-6981 is a highly potent and selective blocker of N-methyl-d-aspartate receptors that has been shown to possess both rapid and sustained antidepressant activity. In the present study, we report the biopharmaceutical characterization of Ro 25-6981 by evaluating gastrointestinal stability, transepithelial permeability, stability in human liver microsomes, and in silico metabolic prediction. Moreover, in vivo efficacy of Ro 25-6981 after oral administration was evaluated in animal models of depression. When mixed with 5 different simulated gastrointestinal fluids, no loss of parent compound was observed after 6 h, indicating compound stability in the gastrointestinal environment. At the tested concentrations, Ro 25-6981 was shown to have transepithelial permeability with apparent permeability (P_app) values comparable to highly permeable drugs. Ro 25-6981 was metabolized within 30 min in human liver microsomes, and the metabolic prediction data showed glucuronidation and sulfation as potential metabolic pathways. The in vivo efficacy data suggested that Ro 25-6981, when administered orally at 30 mg/kg, exhibits antidepressant-like activity following oral administration with efficacy comparable to traditional antidepressants that is both dose- and time-dependent. Overall, due to optimal gastrointestinal stability, oral permeability, and oral efficacy, Ro 25-6981 can be a potential therapeutic option for the treatment of depression.

Resveratrol derivatives as a pharmacological tool

Prodrugs of resveratrol are under development. Among the long-term goals, still largely elusive, are (1) modulating physical properties (e.g., water-soluble derivatives bearing polyethylene glycol chains), (2) changing distribution in the body (e.g., galactosyl derivatives restricted to the intestinal lumen), (3) increasing absorption from the gastrointestinal tract (e.g., derivatives imitating the natural substrates of endogenous transporters), and (4) hindering phase II metabolism (e.g., temporarily blocking the hydroxyls), all contributing to (5) increasing bioavailability. The chemical bonds that have been tested for functionalization include carboxyester, acetal, and carbamate groups. A second approach, which can be combined with the first, seeks to reinforce or modify the biochemical activities of resveratrol by concentrating the compound at specific subcellular sites. An example is provided by mitochondria-targeted derivatives. These proved to be pro-oxidant and cytotoxic in vitro, selectively killing fast-growing and tumor cells when supplied in the low micromolar range. This suggests the possibility of anticancer applications.

Synthesis and Reactivity of 5-Substituted Furfuryl Carbamates via Oxanorbornadienes

Furfuryl carbamates are labile and require care to be accessed by activating furfuryl alcohols. An alternative oxanorbornadiene (OND)-based strategy is presented for the preparation of 5-R-substituted furfuryl carbamates via the reactions of amines with intermediate OND carbonates. The resulting OND carbamates, which are stable for several months, undergo thiol mediated retro-Diels-Alder reaction to deliver the desired furfuryl carbamates in a single flask. Conditions for the selective hydrolysis of furfuryl carbamates in the presence of tert-butyloxycarbonyl (Boc) groups were identified, and it was shown that furfuryl carbamates can be used as a prodrug handle.

New natural amino acid-bearing prodrugs boost pterostilbene's oral pharmacokinetic and distribution profile

The biomedical effects of the natural phenol pterostilbene are of great interest but its bioavailability is negatively affected by the phenolic group in position 4' which is an ideal target for the conjugative enzymes of phase II metabolism. We report the synthesis and characterization of prodrugs in which the hydroxyl moiety is reversibly protected as a carbamate ester linked to the N-terminus of a natural amino acid. Prodrugs comprising amino acids with hydrophobic side chains were readily absorbed after intragastric administration to rats. The Area Under the Curve for pterostilbene in blood was optimal when prodrugs with isoleucine or β-alanine were used. The prodrug incorporating isoleucine was used for further studies to map distribution into major organs. When compared to pterostilbene itself, administration of the isoleucine prodrug afforded increased absorption, reduced metabolism and higher concentrations of pterostilbene, sustained for several hours, in most of the organs examined. Experiments using Caco-2 cells as an in vitro model for human intestinal absorption suggest that the prodrug could have promising absorption profiles also in humans; its uptake is partly due to passive diffusion, and partly mediated by H⁺-dependent transporters expressed on the apical membrane of enterocytes, such as PepT1 and OATP.

Resveratrol: How Much Wine Do You Have to Drink to Stay Healthy?

Resveratrol is a naturally occurring stilbene endowed with multiple health-promoting effects. It is produced by certain plants including several dietary sources such as grapes, apples, raspberries, blueberries, plums, peanuts, and products derived therefrom (e.g., wine). Resveratrol can be isolated and purified from these biological sources or synthesized in a few steps with an overall high yield. This compound and its glucoside, the trans-polydatin piceid, have received worldwide attention for their beneficial effects on cardiovascular, inflammatory, neurodegenerative, metabolic, and age-related diseases. These health-promoting effects are particularly attractive given the prevalence of resveratrol-based nutraceuticals and the paradoxical epidemiologic observation that wine consumption is inversely correlated to the incidence of coronary heart disease. However, the notion of resveratrol as a "magic bullet" was recently challenged by clinical trials showing that this polyphenol does not have a substantial influence on health status and mortality risk. In the present review, we discuss the proposed therapeutic attributes and the mode of molecular actions of resveratrol. We also cover recent pharmacologic efforts to improve the poor bioavailability of resveratrol and influence the transition between body systems in humans. We conclude with some thoughts about future research directions that might be meaningful for resolving controversies surrounding resveratrol.

Real-time self-tracking of an anticancer small molecule nanodrug based on colorful fluorescence variations

A self-tracking drug delivery system was constructed using two anticancer drugs, resulting in colorful fluorescence variations during drug delivery.