A rapid HPLC method for the quantification of 3,5,4′-trimethoxy-trans-stilbene (TMS) in rat plasma and its application in pharmacokinetic study

Effect of resveratrol and curcumin and the potential synergism on hypertension: A mini-review of human and animal model studies

Resveratrol (RES) and curcumin (CUR) are two of the most extensively studied bioactive compounds in cardiovascular research from the past until today. These compounds have effectively lowered blood pressure by downregulating the renin-angiotensin system, exerting antioxidant effects, and exhibiting antiproliferative activities on blood vessels. This study aims to summarize the results of human and animal studies investigating the effects of CUR, RES, and their combination on hypertension and the molecular mechanisms involved. The published trials' results are controversial regarding blood pressure reduction with different doses of RES and CUR, highlighting the need to address this issue.

Phytostilbenes as agrochemicals: biosynthesis, bioactivity, metabolic engineering and biotechnology

Covering: 1976 to 2020. Although constituting a limited chemical family, phytostilbenes represent an emblematic group of molecules among natural compounds. Ever since their discovery as antifungal compounds in plants and their ascribed role in human health and disease, phytostilbenes have never ceased to arouse interest for researchers, leading to a huge development of the literature in this field. Owing to this, the number of references to this class of compounds has reached the tens of thousands. The objective of this article is thus to offer an overview of the different aspects of these compounds through a large bibliography analysis of more than 500 articles. All the aspects regarding phytostilbenes will be covered including their chemistry and biochemistry, regulation of their biosynthesis, biological activities in plants, molecular engineering of stilbene pathways in plants and microbes as well as their biotechnological production by plant cell systems.

Whole-cell biocatalytic, enzymatic and green chemistry methods for the production of resveratrol and its derivatives

Resveratrol and the biosynthetically related stilbenes are plant secondary metabolites with diverse pharmacological effects. The versatile functions of these compounds in plant defense mechanisms as phytoalexins on one hand, and in human health as potential pharmaceutical agents on the other, have attracted lots of interest in recent years to understand their biosynthetic pathways and their biological properties. Because of difficulties in obtaining resveratrol and its glucosylated derivatives as well as oligomeric forms in sufficient amounts for evaluation of their activity by plant sourcing or total synthesis, biotechnology may provide a competitive approach for the large-scale and low cost production of biologically active stilbenes. Additionally, one major limitation in the use of resveratrol and related aglycone derivatives as therapeutic agents is associated with their inherent poor aqueous solubility and low bioavailability. This article examines approaches for the synthesis of potential pharmacologically resveratrol derivatives in vivo by exploiting whole microorganisms, enzymatic and biocatalytic approaches allowing their full utilization for medicine, food and cosmetic applications. These methods also have the advantage of enabling the one-step production of stilbene compounds, compared to the time-consuming and environmentally unfriendly procedures used for their total synthesis or their extraction from plants. Increasing the desired products yield and biological activity through glucosylation (β-D-glucosides versus α-D-glucosides) and oligomerization methodologies of resveratrol including green chemistry methods in organic solvent-free media are discussed as well.

Resveratrol Directly Controls the Activity of Neuronal Ryanodine Receptors at the Single-Channel Level

Calcium ion dyshomeostasis contributes to the progression of many neurodegenerative diseases and represents a target for the development of neuroprotective therapies, as reported by Duncan et al. (Molecules 15(3):1168-95, 2010), LaFerla (Nat Rev Neurosci 3(11):862-72, 2002), and Niittykoshi et al. (Invest Ophthalmol Vis Sci 51(12):6387-93, 2010). Dysfunctional ryanodine receptors contribute to calcium ion dyshomeostasis and potentially to the pathogenesis of neurodegenerative diseases by generating abnormal calcium ion release from the endoplasmic reticulum, according to Bruno et al. (Neurobiol Aging 33(5):1001 e1-6, 2012) and Stutzmann et al. (J Neurosci 24(2):508-13, 2004). Since ryanodine receptors share functional and structural similarities with potassium channels, as reported by Lanner et al. (Cold Spring Harb Perspect Biol 2(11):a003996, 2010), and small molecules with anti-oxidant properties, such as resveratrol (3,5,4'-trihydroxy-trans-stilbene), directly control the activity of potassium channels, according to Wang et al. (J Biomed Sci 23(1):47, 2016), McCalley et al. (Molecules 19(6):7327-40, 2014), Novakovic et al. (Mol Hum Reprod 21(6):545-51, 2015), Li et al. (Cardiovasc Res 45(4):1035-45, 2000), Gopalakrishnan et al. (Br J Pharmacol 129(7):1323-32, 2000), and Hambrock et al. (J Biol Chem 282(5):3347-56, 2007), we hypothesized that trans-resveratrol can modulate intracellular calcium signaling through direct binding and functional regulation of ryanodine receptors. The goal of our study was to identify and measure the control of ryanodine receptor activity by trans-resveratrol. Mechanisms of calcium signaling mediated by the direct interaction between trans-resveratrol and ryanodine receptors were identified and measured with single-channel electrophysiology. Addition of trans-resveratrol to the cytoplasmic face of the ryanodine receptor increased single-channel activity at physiological and elevated pathophysiological cytoplasmic calcium ion concentrations. The open probability of the channel increases after interacting with the small molecule in a dose-dependent manner, but remains also dependent on the concentration of its physiological ligand, cytoplasmic-free calcium ions. This study provides the first evidence of a direct functional interaction between trans-resveratrol and ryanodine receptors. Such functional control of ryanodine receptors by trans-resveratrol as a novel mechanism of action could provide additional rationales for the development of novel therapeutic strategies to treat and prevent neurodegenerative diseases.

Evaluation of the effect of the new methoxy-stilbenes on expression of receptors and enzymes involved in estrogen synthesis in cancer breast cells

Our previous study showed that the new synthetic methoxy-stilbenes, 3,4,2'-trimethoxy-trans-stilbene (3MS), 3,4,2',4'-tetramethoxy-trans-stilbene (4MS), and 3,4,2',4',6'-pentamethoxy-trans-stilbene (5MS), modulate the constitutive expression of enzymes and receptors involved in estrogen metabolism in breast immortalized epithelial MCF10 cells. In this study, we evaluated the effect of 3MS, 4MS, and 5MS in comparison to resveratrol activity in MCF7 estrogen-dependent and MDA-MB-231 estrogen-independent breast cancer cell lines. 3MS similarly to resveratrol reduced the expression of estrogen receptor α in MCF7 cells. However, in these cells, 5MS reduced the most CYP19, the gene encoding aromatase, at mRNA transcript level. In contrast, in the MDA-MB-231 cells, the most efficient inhibitor of CYP19 expression was 3MS, reducing the level of its protein by ~ 25%. This stilbene also inhibited the aromatase activity in a recombinant protein system with IC₅₀ value ~ 85 µM. Treatment with the methoxy-stilbenes reduced the level of estradiol in culture medium. The most significant reduction was exerted by 3MS. None of the tested stilbenes including resveratrol changed significantly the expression of AhR, although CYP1A1 protein level was slightly reduced in MDA-MB-231 cells, while CYP1B1 expression was increased in these cells as a result of treatment with 3MS, but only at the transcript level. Overall, these results show weak or moderate effect of the new methoxy-stilbenes on the expression of key proteins involved in estrogens metabolism in cancer breast cells. However, the reduced CYP19 expression and activity upon 3MS treatment in metastatic MDA-MB-231 cells require the further studies.

Therapeutic Versatility of Resveratrol Derivatives

Resveratrol, a natural phytoalexin, exhibits a remarkable range of biological activities, such as anticancer, cardioprotective, neuroprotective and antioxidant properties. However, the therapeutic application of resveratrol was encumbered for its low bioavailability. Therefore, many researchers focused on designing and synthesizing the derivatives of resveratrol to enhance the bioavailability and the pharmacological activity of resveratrol. During the past decades, a large number of natural and synthetic resveratrol derivatives were extensively studied, and the methoxylated, hydroxylated and halogenated derivatives of resveratrol received particular more attention for their beneficial bioactivity. So, in this review, we will summarize the chemical structure and the therapeutic versatility of resveratrol derivatives, and thus provide the related structure activity relationship reference for their practical applications.

The effect of resveratrol, its naturally occurring derivatives and tannic acid on the induction of cell cycle arrest and apoptosis in rat C6 and human T98G glioma cell lines

Resveratrol (3,5,4'-trihydroxy-trans-stilbene) is a potent chemopreventive and potentially cancer therapeutic agent. Since rapid metabolism limits resveratrol bioavailability, derivatives less prone to metabolic transformation are being sought and tested. We evaluated the effect of resveratrol, and its analogs (pterostilbene and 3,5,4'-trimethoxystilbene) along with tannic acid, on cell cycle and apoptosis in rat C6 and human T98G glioma cells. At concentration ranges both lower and higher than IC₅₀ calculated based on MTT assay, all these polyphenols affected the cell cycle distribution. However, resveratrol and pterostilbene increased the percentage of the cells in S phase, while trimethoxystilbene (TMS) caused a massive accumulation of cells at the G2/M phase of the cell cycle. Tannic acid had no effect on cell cycle distribution in C6 cells, but increased the number of dead cells in both glioma cell lines. The ability to induce apoptosis by tannic acid and stilbenes was confirmed by phosphatidylserine externalization, the loss of mitochondrial membrane potential and the level of cleaved caspase-3. The apoptosis rate was most significantly increased by TMS and this was related to p53 induction. These results indicate that methoxylated stilbenes are efficient inhibitors of glioma cell proliferation and apoptosis inducers and might be considered adjuvants in glioma therapy.

Anticancer Activity of Stilbene-Based Derivatives

Stilbene is an abundant structural scaffold in nature, and stilbene-based compounds have been widely reported for their biological activity. Notably, (E)-resveratrol and its natural stilbene-containing derivatives have been extensively investigated as cardioprotective, potent antioxidant, anti-inflammatory, and anticancer agents. Starting from its potent chemotherapeutic activity against a wide variety of cancers, the stilbene scaffold has been subject to synthetic manipulations with the aim of obtaining new analogues with improved anticancer activity and better bioavailability. Within the last decade, the majority of new synthetic stilbene derivatives have demonstrated significant anticancer activity against a large number of cancer cell lines, depending on the type and position of substituents on the stilbene skeleton. This review focuses on the structure-activity relationship of the key compounds containing a stilbene scaffold and describes how the structural modifications affect their anticancer activity.

Biological actions and molecular effects of resveratrol, pterostilbene, and 3'-hydroxypterostilbene

Stilbenes are a class of polyphenolic compounds, naturally found in a wide variety of dietary sources such as grapes, berries, peanuts, red wine, and some medicinal plants. There are several well-known stilbenes including trans-resveratrol, pterostilbene, and 3′-hydroxypterostilbene. The core chemical structure of stilbene compounds is 1,2-diphenylethylene. Recently, stilbenes have attracted extensive attention and interest due to their wide range of health-beneficial effects such as anti-inflammation, -carcinogenic, -diabetes, and -dyslipidemia activities. Moreover, accumulating in vitro and in vivo studies have reported that stilbene compounds act as inducers of multiple cell-death pathways such as apoptosis, cell cycle arrest, and autophagy for chemopreventive and chemotherapeutic agents in several types of cancer cells. The aim of this review is to highlight recent molecular findings and biological actions of trans-resveratrol, pterostilbene, and 3′-hydroxypterostilbene.

Pharmacokinetics, bioavailability, metabolism and excretion of δ-viniferin in rats

A highly rapid and sensitive liquid chromatographic-electrospray ionization tandem mass spectrometric (LC-ESI-MS/MS) method was developed and validated for the determination of trans-δ-viniferin (Rs-1) in rat plasma, urine and feces. All biological samples were prepared by liquid-liquid extraction and hesperetin was included as an internal standard (IS). Chromatographic separation was achieved on a shim-pack XR-ODS column using a gradient mobile phase. MS/MS detection was performed by negative ion electrospray ionization. The method was sensitive with a lower limit of quantification of 1.42 ng/mL and linear over the range of 1.42-2172 ng/mL in all matrices. The method was applied to study the pharmacokinetics, bioavailability, metabolism, and excretion of Rs-1 in rats following a single oral or intravenous dose. Two metabolites, Rs-1 glucuronide and Rs-1 sulfate, were detected in plasma and in urine after administration of Rs-1. The absolute oral bioavailability of Rs-1 was 2.3%, and the total absorption rose to 31.5% with addition of its glucuronide and sulfate metabolites. Only 0.09% of the gavaged dose, including Rs-1 and metabolites, was excreted in the urine, while 60.3% was found in the feces in unchanged form. The results indicate that both poor absorption and extensive metabolism were the important factors that led to the poor bioavailability of Rs-1, which can provide a basis for further studies on structural modification and dosage form design.

Synthesis and cytotoxic activities of E-resveratrol derivatives

The present study was designed to synthesize derivatives of E-resveratrol and evaluate their cytotoxic activity in vitro. Different functional groups were conjugated with the phenolic hydroxyl group of E-resveratrol, and the double bond of E-resveratrol was reduced. The in vitro cytotoxicity of the synthetic derivatives was evaluated against three tumor cell lines (A549, LAC, and HeLa) using the MTT assay. Twenty-six E-resveratrol derivatives were synthesized and their structures were confirmed by (1)H NMR, MS, IR, and elemental analyses. Compounds 1-6, 12, 15-21, and 23-26 were reported for the first time. Among them, Compounds 1, 2, 4, 5, and 9-11, showed significant cytotoxicity against tumor cells; especially, Compound 1 showed an IC50 value of 4.38 μmol · L(-1) in the A549 cells which was 15-fold more active than E-resveratrol; Compound 9 showed an IC50 value of 1.41 μmol · L(-1) in the HeLa cell line which was 90-fold more active than E-resveratrol, and close to adriamycin. The structure-activity relationships were also investigated. Compounds 1, 2 and 9-11 may serve as potential lead compounds for the discovery of new anticancer drugs.

Resveratrol-Related Polymethoxystilbene Glycosides: Synthesis, Antiproliferative Activity, and Glycosidase Inhibition

A small library of polymethoxystilbene glycosides (20-25) related to the natural polyphenol resveratrol have been synthesized and subjected, together with their aglycones 17-19, to an antiproliferative activity bioassay toward Caco-2 and SH-SY5Y cancer cells. Six of the compounds exhibit antiproliferative activity against at least one cell line. In particular, compounds 17 and 18 proved highly active on at least one of the two cell cultures. Compound 18 showed a GI50 value of 3 μM against Caco-2 cells, a value comparable to that of the anticancer drug 5-fluorouracil. The closely related compound 19 proved inactive, and its conjugates 22 and 25 showed weak cell growth inhibition. The results indicate that minimal differences in the structure of both polymethoxystilbenes and their glycosides can substantially affect the antiproliferative activity. The possible hydrolytic release of the aglycones 17-19 by β-glucosidase or β-galactosidase was also evaluated. Compounds 20-25 were also tested as potential β-glucosidase, β-galactosidase, and α-glucosidase inhibitors. A promising inhibitory activity toward α-glucosidase was observed for 21 (IC50 = 78 μM) and 25 (IC50 = 70 μM), which might be indicative of their potential as lead compounds for development of antidiabetic or antiobesity agents.

Pterostilbene, an Active Constituent of Blueberries, Stimulates Nitric Oxide Production via Activation of Endothelial Nitric Oxide Synthase in Human Umbilical Vein Endothelial Cells

Endothelial dysfunction, a key process in development of cardiovascular diseases, is largely due to reduced nitric oxide (NO) derived from endothelial NO synthase (eNOS). Resveratrol has been reported to stimulate NO production via estrogen receptor α (ERα) activation in endothelial cells. Here, we investigated whether two natural methylated analogs of resveratrol, pterostilbene (Pts) and trans-3,5,4'-trimethoxystilbene (TMS), similarly to resveratrol, could influence endothelial NO release in human umbilical vein endothelial cells (HUVECs). In HUVECs exposed to Pts or TMS, NO production and phosphorylation of eNOS, protein kinase B (Akt), and ERα were measured by using a fluorimetric NO assay kit and Western blot analysis, respectively. Dimethylated Pts, but not trimethylated TMS, stimulated dose-dependent NO production via eNOS phosphorylation. Pts also stimulated dose-dependent phosphorylation of Akt, but not of ERα. NO production and eNOS phosphorylation in response to Pts were significantly abolished by the phosphoinositide 3-kinase (PI3K)/Akt inhibitor LY294002, but not by the ERα antagonist ICI182780. Our results suggest that Pts, but not TMS, is capable of inducing eNOS phosphorylation and the subsequent NO release, presumably, by activating PI3K/Akt pathway. The potential efficacy of Pts, an active constituent of blueberries, may aid in the prevention of cardiovascular diseases characterized by endothelial dysfunction.

Epigenetic potential of resveratrol and analogs in preclinical models of prostate cancer

Lifestyle, particularly diet, is a risk factor for prostate cancer. Dietary polyphenols such as resveratrol possess anticancer properties and therefore have chemopreventive and therapeutic potential. Resveratrol has pleiotropic effects, exerting its biological activity through multiple pathways and targets, including those associated with cancer. Numerous studies have demonstrated the anticancer effects of resveratrol and, to a lesser extent, its analogs, in tissue culture, while in vivo observations are limited. Here, we provide a concise summary of our results on epigenetic mechanisms of resveratrol and analogs mediated through regulation of chromatin modifier metastasis-associated protein 1 (MTA1) and microRNAs (miRNAs), and highlight the anticancer effects of these compounds in preclinical models of prostate cancer. We suggest that the identified stilbene responsive mechanism-based biomarkers, such as MTA1 and oncogenic miRNAs, may become indicative of treatment efficacy in prostate cancer. Resveratrol analogs with better bioavailability, conferring superior pharmacological potencies and greater anticancer effects, may become stronger candidates for clinical development.

Neuroprotective effects of resveratrol in Alzheimer disease pathology

Alzheimer's disease is a chronic neurodegenerative disorder characterized by a progressive loss of cognitive and behavioral abilities. Extracellular senile plaques and intracellular neurofibrillary tangles are hallmarks of AD. Researchers aim to analyze the molecular mechanisms underlying AD pathogenesis; however, the therapeutic options available to treat this disease are inadequate. In the past few years, several studies have reported interesting insights about the neuroprotective properties of the polyphenolic compound resveratrol (3, 5, 4'-trihydroxy-trans-stilbene) when used with in vitro and in vivo models of AD. The aim of this review is to focus on the neuroprotective and antioxidant effects of resveratrol on AD and its multiple potential mechanisms of action. In addition, because the naturally occurring forms of resveratrol have a very limited half-life in plasma, a description of potential analogs aimed at increasing the bioavailability in plasma is also discussed.

Inhibition of CYP17A1 activity by resveratrol, piceatannol, and synthetic resveratrol analogs

BACKGROUND

Resveratrol (RSV) and resveratrol analogs have a potential use in prostate cancer chemoprevention due to effects on for example, cell growth, apoptosis, angiogenesis, and metastasis. However, inhibition of CYP17A1, a key enzyme in the androgen biosynthesis and a target for prostate cancer therapy, has not been explored as a possible mechanism behind the effects on prostate cancer.

METHODS

Human adrenocortical carcinoma cells, H295R, were treated with RSV, piceatannol (PIC), 3,5,4'-triacetylresveratrol (RSVTA), 3,5-diacetylresveratrol (RSVDA), and 3,5,4'-trimethylresveratrol (RSVTM) for 24 hr at concentrations of 1, 5, 10, 25, and 50 µM. Steroid secretion, enzyme activities, and gene expression of key steps in steroidogenesis were investigated.

RESULTS

Secretion of dihydroepiandrosterone (DHEA), testosterone, and cortisol were drastically decreased by all test compounds at concentrations that did not affect cell viability. Progesterone and aldosterone secretion were increased. This steroid secretion pattern can be explained by the demonstrated inhibition of CYP17A1 enzyme activity. The most efficient CYP17A1 inhibitors were the synthetic analogs RSVTA, RSVDA, and RSVTM. Inhibition by RSVTM was more selective on the 17,20-lyase activity than hydroxylase activity of CYP17A1. Treatment of cells with all compounds, except RSVTM, caused increased estradiol levels, which could be explained by the demonstrated inhibition of estrogen sulfate conjugation, catalyzed by SULT1E1.

CONCLUSIONS

Our results on CYP17A1 inhibition of RSV and RSV analogs suggest a novel mechanism for chemoprevention of prostate cancer by resveratrol and the analogs. Especially RSVTM, which has a preferential inhibition on the 17,20-lyase activity of CYP17A1, may be a promising candidate for prostate cancer chemoprevention.

Differential effects of resveratrol and its natural analogs, piceatannol and 3,5,4'-trans-trimethoxystilbene, on anti-inflammatory heme oxigenase-1 expression in RAW264.7 macrophages

Resveratrol (Res) and its two natural analogs that are also related to Res metabolism, piceatannol (Pic) and 3,5,4'-trans-trimethoxystilbene (TMS), were compared in their ability to suppress lipopolysaccharide (LPS)-induced production of proinflammatory tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) and to induce anti-inflammatory heme oxygenase-1 (HO-1) expression in RAW264.7 macrophages. At non-cytotoxic concentrations, they differentially suppressed LPS-induced production of TNF-α and IL-1β; the relative potency for suppression of TNF-α and IL-1β production was Pic > Res > TMS. Res and Pic differentially induced HO-1 expression; Pic, which possesses four hydroxyl groups, was more active in inducing HO-1 expression than Res that contains three hydroxyl groups. TMS, which has none of hydroxyl groups, failed to induce HO-1 expression. These findings suggest that the hydroxyl groups of Res analogs are important for suppression of TNF-α and IL-1β production and HO-1 expression. Interestingly, protoporphyrin-IX, a competitive inhibitor of HO-1 activity, partly attenuated the inhibitory effects of Res and Pic (but not TMS) on TNF-α and IL-1β production, suggesting that suppression of TNF-α and IL-1β production correlates at least in part with HO-1 expression. Overall, the ability of Res analogs to induce HO-1 expression may provide one of possible mechanisms of their anti-inflammatory action.

Trimethoxy-resveratrol and piceatannol administered orally suppress and inhibit tumor formation and growth in prostate cancer xenografts

BACKGROUND

Resveratrol (Res) is recognized as a promising cancer chemoprevention dietary polyphenol with antioxidative, anti-inflammatory, and anticancer properties. However, the role of its analogues in prostate cancer (PCa) chemoprevention is unknown.

METHODS

We synthesized several natural and synthetic analogues of Res and characterized their effects on PCa cells in vitro using a cell proliferation assay. A colony formation assay and in vitro validation of luciferase (Luc) activity was done for LNCaP-Luc cells that were consequently used for in vivo studies. The efficacy of Res, trimethoxy-resveratrol (3M-Res) and piceatannol (PIC) was studied in a subcutaneous (s.c.) model of PCa using oral gavage. Tumor progression was monitored by traditional caliper and bioluminescent imaging. The levels of cytokines in serum were examined by ELISA, and the levels of compounds in serum and tumor tissues were determined by gas chromatography-mass spectrometry.

RESULTS

We examined the anti-proliferative activities of Res/analogues in three PCa cell lines. We further compared the chemopreventive effects of oral Res, 3M-Res, and PIC in LNCaP-Luc-xenografts. We found that 2 weeks pretreatment with the compounds diminished cell colonization, reduced tumor volume, and decreased tumor growth in the xenografts. Both 3M-Res and PIC demonstrated higher potency in inhibiting tumor progression compared to Res. Notably, 3M-Res was the most active in inhibiting cell proliferation and suppressing colony formation, and its accumulation in both serum and tumor tissues was the highest.

CONCLUSIONS

Our findings offer strong pre-clinical evidence for the utilization of dietary stilbenes, particularly 3M-Res, as novel, potent, effective chemopreventive agents in PCa.

Design, synthesis and structure-activity relationships of some novel, highly potent anti-invasive (E)- and (Z)-stilbenes

In our ongoing exploration of the structure-activity landscape of anti-invasive chalcones, we have prepared and evaluated a number of structurally related (E)- and (Z)-stilbenes. These molecules exhibited an extraordinary high in vitro potency in the chick heart invasion assay, being active up to 10nmolL(-1), a concentration level a 100-fold lower than the lowest effective doses that have been reported for natural analogues. Furthermore, they possess an interesting pharmacological profile in silico.

Quantification of trans-2,6-difluoro-4'-N,N-dimethylaminostilbene in rat plasma: application to a pharmacokinetic study

trans-2,6-Difluoro-4'-N,N-dimethylaminostilbene (DFS), a synthetic stilbene, displayed potent pre-clinical anti-cancer activities exceeding that observed for naturally occurring resveratrol. In this study, a simple and sensitive HPLC method was developed and validated to quantify DFS in rat plasma. The lower limit of quantification (LLOQ) was 5 ng/ml. The intra- and inter-day variation in terms of relative standard deviation (RSD) was all less than 10%. The bias rate ranged from -11.5% to 6.2% while the absolute recovery ranged from 94.1 ± 2.3 to 97.3 ± 4.4%. The pharmacokinetic profiles of DFS were examined in Sprague-Dawley rats after intravenous administration (2 mg/kg). DFS displayed moderate clearance (Cl=61.5 ± 17.7 ml/min/kg) and a relatively prolonged terminal elimination half-life (t(1/2 λz)) of 351 ± 180 min. Aqueous solubility played a crucial role in the oral absorption of DFS. When DFS was given as a suspension (6 mg/kg), the absolute oral bioavailability (F) was almost negligible. However, when DFS was given in a solution prepared with hydroxypropyl-β-cyclodextrin (6 mg/kg), the F was 12.4 ± 10.7%. Dose-escalation to 15 mg/kg resulted in much higher systemic exposure (F=40.2 ± 10.0%). As DFS is orally available after formulation with hydroxypropyl-β-cyclodextrin and pharmacologically active systemic concentrations could be achieved after a single oral dose, the use of DFS as a cancer chemopreventive/chemotherapeutic agent is possible.

Enhanced bioavailability after oral and pulmonary administration of baicalein nanocrystal

The aim of the study was to investigate the potential of oral and pulmonary nanocrystal to enhance the bioavailability of baicalein, a bioactive flavonoid isolated from the root of Scutellaria baicalensis Georgi. So far, the nano-sized delivery system of baicalein and its pulmonary delivery have received no exploration. In the present investigation, the baicalein nanocrystal was prepared by anti-solvent recrystallization followed by high pressure homogenization. In vitro characterization was performed including particle size and distribution, Zeta potential, dissolution, scanning electron microscopy, differential scanning calorimetry and X-ray powder diffractometry. It was indicated that no crystalline change was observed after nanocrystal preparation. The baicalein nanocrystal containing only trace of stabilizer exhibited a significantly enhanced dissolution of baicalein. In vivo test was also carried out in rats and pharmacokinetic parameters of the baicalein crystal and the baicalein nanocrystal after gavage and pulmonary administration were compared, based on the simultaneous determination of baicalein and baicalin by high performance liquid chromatography. The mean relative bioavailability of oral baicalein nanocrystal was 1.67-fold that of oral baicalein crystal. The pulmonary baicalein nanocrystal had rapid and extensive absorption and had almost identical pharmacokinetic parameters to intravenous baicalein injection.

Quantification of α- and β-amyrin in rat plasma by gas chromatography-mass spectrometry: application to preclinical pharmacokinetic study

α- and β-Amyrins are naturally occurring triterpenes with a wide range of biological activities. In this study, a reliable GC-MS method was developed and validated for the quantification of α- and β-amyrins in rat plasma. The calibration curves were linear (R(2) > 0.996) with a limit of quantification of 1.0 ng ml(-1) for both α- and β-amyrins. The precision and repeatability of this method was good as the relative standard deviation were 12% or less. The absolute recovery ranged from 71% to 89%, while the analytical recovery ranged from 95% to 99%. The pharmacokinetic profiles of α- and β-amyrins in rats were subsequently investigated in Sprague-Dawley rats. β-Amyrin was administered intravenously and also orally in two forms, namely, as a suspension of the pure compound and the crude plant extract. α-Amyrin was administered orally as a suspension of the crude plant extract. β-Amyrin had a very long terminal elimination half-life (t(1/2λz) = 610 ± 179 min) and extremely slow clearance (Cl = 2.04 ± 0.24 ml min(-1) kg(-1)). The absolute oral bioavailability of β-amyrin in the crude plant extract was about fourfold higher than that in the suspension of pure form (3.83% vs 0.86%). When given in crude plant extract, both α- and β-amyrins had a similar dose normalized C(max). This reliable GC-MS method will enable further pharmacokinetic investigations of α- and β-amyrins.

Preclinical pharmacokinetic evaluation of resveratrol trimethyl ether in sprague-dawley rats: the impacts of aqueous solubility, dose escalation, food and repeated dosing on oral bioavailability

Resveratrol trimethyl ether (trans-3,5,4'-trimethoxystilbene, RTE) is a naturally occurring and pharmacologically active resveratrol derivative. To evaluate its suitability as a drug candidate, a pharmacokinetic study was carried out in Sprague-Dawley rats with the emphasis to identify the impact of aqueous solubility, dose escalation, food, and repeated dosing on its oral bioavailability. Upon single intravenous administration (5 mg/kg), RTE displayed moderate clearance (35.5 ± 5.3 mL/min/kg) and a fairly long terminal elimination half-life (511 ± 136 min); dose escalation (5-20 mg/kg) did not cause nonlinear pharmacokinetics. When given orally in suspension (60 mg/kg), RTE was poorly absorbed with negligible bioavailability (< 1.5%), fasting further decreased its bioavailability (<1%). However, when administered in a solution formulated with randomly methylated-β-cyclodextrin (15 mg/kg), RTE was rapidly absorbed with good bioavailability (46.5 ± 4.8%). Dose escalation resulted in increased bioavailability (64.6 ± 8.0%) at the dose of 60 mg/kg. Repeated RTE dosing (7 daily oral doses) did not alter the clearance, terminal elimination half-life and bioavailability. In summary, the aqueous solubility of RTE was a barrier to oral absorption; repeated RTE administrations did not alter its pharmacokinetic profiles; as RTE possessed appropriate pharmacokinetic profiles, further investigation on RTE as a drug candidate is warranted.

Bioavailability of resveratrol

This paper reviews our current understanding of the absorption, bioavailability, and metabolism of resveratrol, with an emphasis on humans. The oral absorption of resveratrol in humans is about 75% and is thought to occur mainly by transepithelial diffusion. Extensive metabolism in the intestine and liver results in an oral bioavailability considerably less than 1%. Dose escalation and repeated dose administration of resveratrol does not appear to alter this significantly. Metabolic studies, both in plasma and in urine, have revealed major metabolites to be glucuronides and sulfates of resveratrol. However, reduced dihydroresveratrol conjugates, in addition to highly polar unknown products, may account for as much as 50% of an oral resveratrol dose. Although major sites of metabolism include the intestine and liver (as expected), colonic bacterial metabolism may be more important than previously thought. Deconjugation enzymes such as β-glucuronidase and sulfatase, as well as specific tissue accumulation of resveratrol, may enhance resveratrol efficacy at target sites. Resveratrol analogs, such as methylated derivatives with improved bioavailability, may be important in future research.

Quantification of trans-3,4,5,4'-Tetramethoxystilbene in rat plasma by HPLC: application to pharmacokinetic study

A simple HPLC method was established to quantify trans-3,4,5,4'-tetramethoxystilbene (MR-4 or DMU-212) in rat plasma. Chromatographic separation was obtained with a reversed-phase HPLC column through an 11 min gradient delivery of a mixture of acetonitrile and water at a flow rate of 1.5 mL/min at 50 °C. The limit of quantification was 15 ng/mL. The intra- and interday precisions in terms of relative standard deviation were <9% at all concentrations. Similarly, the accuracy was good, and the bias rates ranged within ±7%. The pharmacokinetic profiles of MR-4 were subsequently assessed in rats using 2-hydroxypropyl-β-cyclodextrin as a dosing vehicle. Upon intravenous administration, MR-4 displayed moderate clearance (46.5 ± 7.6 mL/min/kg) and terminal elimination half-life (154 ± 80 min). However, the absolute oral bioavailability of MR-4 was low (6.31 ± 3.30%). Future investigation on MR-4 as a chemotherapeutic agent should be focused on colorectal cancers.

Determination of Z-3,5,4'-trimethoxystilbene in rat plasma by a simple HPLC method: application in a pre-clinical pharmacokinetic study

A simple HPLC method had been developed and validated to quantify Z-3,5,4'-trimethoxystilbene (Z-TMS), a phyto-stilbene with potent anti-cancer activities in rat plasma. Chromatographic separation was achieved on a reversed phase-HPLC column, which was protected by a guard column through a 13.5-min gradient delivery of a mixture of acetonitrile and water at a flow rate of 1.5 ml/min at 50 degrees C. The UV absorbance at 300 nm was recorded. Z-TMS and E-stilbene (internal standard) eluted at 8.8 and 9.3 min, respectively. The calibration curve was linear within the range of 33-2500 ng/ml (R(2)>0.9995) and 10 ng/ml was the lower limit of detection. The intra- and inter-day precisions were good and the relative standard deviation was all lower than 10%. The analytical recovery of Z-TMS in plasma ranged from 94.6+/-9.1% to 97.0+/-2.1%. This HPLC method was successfully applied to assess the pharmacokinetic profile of Z-TMS in Sprague-Dawley rats using hydroxypropyl-beta-cyclodextrin (HP-beta-CyD) as a dosing vehicle. Although Z-TMS displayed negligible oral bioavailability, it had a fairly long terminal elimination half-life, abundant plasma drug exposure and limited clearance following intravenous administration. As Z-TMS had favorable intravenous pharmacokinetic profile, further investigation on its potential as a cancer chemotherapeutic agent is warranted.

A simple and sensitive HPLC-UV method for the quantification of piceatannol analog trans-3,5,3',4'-tetramethoxystilbene in rat plasma and its application for a pre-clinical pharmacokinetic study

A simple and sensitive HPLC-UV method was developed and validated for the quantification of piceatannol analog trans-3,5,3',4'-tetramethoxystilbene (M-PIC) in rat plasma. Following protein precipitation with three volumes of acetonitrile, the analytes were separated on a RP-HPLC column, which was protected by a guard column through gradient delivery of a mixture of acetonitrile-water at 40 degrees C. The UV absorbance at 325nm was recorded to quantify M-PIC. The retention time of M-PIC and trans-3,5-dimethoxystilbene (internal standard) was 7.4 and 8.4min, respectively. The calibration curves were linear (R(2)>0.9989) with a lower limit of quantification of 15ng/ml. The intra- and inter-day precisions, in terms of RSD, were all lower than 7.5%. The average analytical recovery ranged from 97.0 to 104.3% while the average absolute recovery ranged from 101.8 to 105.0%. This reliable HPLC method was subsequently applied to assess the pharmacokinetic profile of M-PIC in Sprague-Dawley rats using 2-hydroxypropyl-beta-cyclodextrin as a dosing vehicle. The terminal elimination half-life (t(1/2lambdaz)) and clearance (Cl) of M-PIC were 313+/-20min and 33.1+/-3.9ml/min/kg, respectively; and its absolute oral bioavailability was as high as 50.7+/-15.0%. M-PIC appeared to have a favorable pharmacokinetic profile and further pharmacological investigation on this phyto-stilbene was warranted.