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The immediate and delayed metabolic changes in rats treated with valproate (VPA), a drug used for the treatment of epilepsy, were profiled. An established approach using dried blood spots (DBS) as sample matrices for gas chromatography/mass spectrometry-based metabolomics profiling was modified using double solvents in the extraction of analytes. With the modified method, some of the previously undetectable metabolites were recovered and subtle differences in the metabolic changes upon exposure to a single dose of VPA between males and female rats were identified. In male rats, changes in 2-hydroxybutyric acid, pipecolic acid, tetratriacontane and stearic acid were found between the control and treatment groups at various time points from 2.5 h up to 24 h. In contrast, such differences were not observed in female rats, which could be caused by the vast inter-individual variations in metabolite levels within the female group. Based on the measured DBS drug concentrations, clearance and apparent volume of distribution of VPA were estimated and the values were found to be comparable to those estimated previously from full blood drug concentrations. The current study indicated that DBS is a powerful tool to monitor drug levels and metabolic changes in response to drug treatment.

Schizandrol A (SZA) and schizandrol B (SZB) are two active ingredients of Wuzhi capsule (WZC), a Chinese proprietary medicine commonly prescribed to alleviate tacrolimus (FK-506)-induced hepatoxicity in China. Due to their inhibitory effects on cytochrome P450 (CYP) 3A enzymes, SZA/SZB may display drug–drug interaction (DDI) with tacrolimus. To identify the extent of this DDI, the enzymes’ inhibitory profiles, including a 50% inhibitory concentration (IC50) shift, reversible inhibition (RI) and time-dependent inhibition (TDI) were examined with pooled human-liver microsomes (HLMs) and CYP3A5-genotyped HLMs. Subsequently, the acquired parameters were integrated into a physiologically based pharmacokinetic (PBPK) model to quantify the interactions between the SZA/SZB and the tacrolimus. The metabolic studies indicated that the SZB displayed both RI and TDI on CYP3A4 and CYP3A5, while the SZA only exhibited TDI on CYP3A4 to a limited extent. Moreover, our PBPK model predicted that multiple doses of SZB would increase tacrolimus exposure by 26% and 57% in CYP3A5 expressers and non-expressers, respectively. Clearly, PBPK modeling has emerged as a powerful approach to examine herb-involved DDI, and special attention should be paid to the combined use of WZC and tacrolimus in clinical practice.

Propylthiouracil (PTU) is commonly prescribed for the management of hyperthyroidism and thyrotoxicosis. Although the exact mechanism of action is not fully understood, PTU is associated with hepatoxicity in pediatric population. Glucuronidation mediated by uridine 5′-diphospho-glucuronosyltransferases (UGTs), which possess age-dependent expression, has been proposed as an important metabolic pathway of PTU. To further examine the metabolism of PTU, a reliable HPLC-MS/MS method for the simultaneous quantification of PTU and its N-β-D glucuronide (PTU-GLU) was developed and validated. The chromatographic separation was achieved on a ZORBAX Extend-C18 column (2.1 × 50 mm, 1.8 μm) through gradient delivery of a mixture of formic acid, methanol and acetonitrile. The electrospray ionization (ESI) was operated in its negative ion mode while PTU and PTU-GLU were detected by multiple reaction monitoring (MRM). This analytical method displayed excellent linearity, sensitivity, accuracy, precision, recovery and stability while its matrix effect and carry-over were insignificant. Subsequently, the in vitro metabolism of PTU was assessed and UGT1A9 was identified as an important UGT isoform responsible for the glucuronidation of PTU. The information obtained from this study will facilitate future mechanistic investigation on the hepatoxicity of PTU and may optimize its clinical application.

Methimazole (MMI), the first-line anti-thyroid agent used in clinical practice is known to induce hepatotoxicity in patients with Grave's disease (GD), although its exact mechanism remains largely unclear. This cohort study aimed to examine the mechanism of MMI-induced hepatotoxicity using metabolomic approach. A total of 40 GD patients with MMI-induced hepatotoxicity (responders) and 80 GD patients without MMI-induced hepatotoxicity (non-responders) were included in this study and their plasma metabolomics was profiled with targeted gas chromatography-tandem mass spectrometry (GC-MS/MS). The plasma levels of 42 metabolites, including glucuronic acid, some amino acids, fatty acids, ethanolamine and octopamine were found to be significantly different between responders and non-responders. In agreement with our previous genotyping data, the genetic polymorphism of uridine 5'-diphospho-glucuronosyltransferase (UGT)1A1*6, which affects the glucuronidation activity and circulating glucuronic acid level was identified as one of the determinants of MMI-induced hepatotoxicity. Plasma level of ethanolamine has a significant correlation with aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities. The pathway analyses further revealed that monoamine oxidase (MAO) inhibition, reactive oxygen species (ROS) production, mitochondria dysfunction, and DNA disruption might contribute to MMI-induced hepatotoxicity. Interestingly, the metabolomic data further suggested the responders had a higher risk of developing osteoporosis and fatty liver disease in comparison to the non-responders. This mechanistic study sheds light on the pathogenesis of MMI-induced hepatotoxicity and prompts personalized prescription of MMI based on UGT1A1*6 genotype in the management of GD.

Periodontitis is a common chronic inflammatory disease driven by the interaction between a dysbiotic oral microbiome and the dysregulated host immune-inflammatory response. Naturally derived nutraceuticals, such as resveratrol and its analogs, are potential adjunctive therapies in periodontal treatment due to their antimicrobial and anti-inflammatory properties. Furthermore, different analogs of resveratrol and the choice of solvents used may lead to varying effects on therapeutic properties. This review presents the current findings and gaps in our understanding on the potential utility of resveratrol and its analogs in periodontal treatment.

The application of physiologically based pharmacokinetic models to nanoparticles is still very restricted and challenging, owing to the complicated in vivo transport mechanisms involving nanoparticles, including phagocytosis, enhanced permeability and retention effects, cellular recognition, and internalisation, enzymatic degradation, lymphatic transport, and changes in physical properties. In our study, five nanoparticle formulations were synthesised using polycaprolactone as a framework material and methoxy poly (ethylene glycol)-poly(ε-caprolactone) as a long-circulating decorating material, as well as types of environmentally responsive near-infrared aza-boron-dipyrromethene dyes. According to quantification data and direct visualisation involving specific organs, a phagocytosis physiologically based pharmacokinetic model was developed to describe the dynamics of nanoparticles within and between organs in mice, considering cellular mechanisms involving phagocytosis and enhanced permeability and retention effects. Our results offer a better understanding of the in vivo fate of polymeric nanoparticles.

Artemether, an artemisinin derivative, is used in the management of life-threatening severe malaria. This study aimed to develop an intravenous dosage form of artemether using nanotechnology. Artemether-loaded zein nanoparticles were prepared by modified antisolvent precipitation using sodium caseinate as a stabilizer. Subsequently, the physicochemical properties of the nanoparticles were characterized, the in vitro hemolytic property was examined with red blood cells, while the pharmacokinetic profile was evaluated in Sprague&ndash, Dawley rats after intravenous administration. The artemether-loaded zein nanoparticles were found to display good encapsulation efficiency, excellent physical stability and offer an in vitro extended-release property. Interestingly, encapsulation of artemether into zein nanoparticles substantially suppressed hemolysis, a common clinical phenomenon occurring after artemisinin-based antimalarial therapy. Upon intravenous administration, artemether-loaded zein nanoparticles extended the mean residence time of artemether by ~80% in comparison to the free artemether formulation (82.9 &plusmn, 15.2 versus 45.6 &plusmn, 16.4 min, p &lt, 0.01), suggesting that the nanoparticles may prolong the therapeutic duration and reduce the dosing frequency in a clinical setting. In conclusion, intravenous delivery of artemether by artemether-loaded zein nanoparticles appears to be a promising therapeutic option for severe malaria.

The risk of drug-induced liver injury (DILI) poses a major challenge for development of natural products derived from traditional Chinese medicines (NP-TCMs). It is urgent to find a new method for the safety assessment of the NP-TCMs. Recent study has reported an in vitro/in silico method to estimate the acceptable daily intake of hepatotoxic compounds using support vector machine (SVM) classifier and physiologically based pharmacokinetic (PBPK) modeling. However, this method is not suitable for estimating the dosing schedule of compounds which are administered in multiple daily doses. Thus, in this study, the method mentioned above was in particular optimized, and used to estimate the hepatotoxic plasma concentrations of 17 NP-TCMs. Additionally, the oral dosing schedules of the triptolide, emodin, matrine and oxymatrine were also predicted by the SVM classifier and PBPK modeling. The optimization included that: (1) in vitro cytotoxicity data of 28 training set compounds was optimized using benchmark concentrations (BMC) modeling; (2) AUC of the training set compound was used as the in vivo metric instead of Cmax to better reflect the total daily exposure of compounds which are administered in multiple daily doses; (3) using the mean AUC in plasma as in vivo metric and BMC value as in vitro metric could achieve the better toxicity separation index (0.962 vs. 0.938); (4) The TSI for Cmax and BMC values was 0.985 calculated in this study, and the results indicated that BMC modeling improved the separation performance. This optimized in vitro-in vivo extrapolation (IVIVE) workflow could extrapolate in vitro BMC to blood concentrations and the oral dosing schedule which are corresponding to certain risk of hepatotoxicity. The estimated safe dosing schedule of oxymatrine by this optimized method was close to the clinical recommended dosing regimen. The results indicate that the optimized method could be used to predict the dosing schedule of compounds administered in multiple daily doses, and our optimized workflow could be helpful for the safety assessment as well as the research and development on NP-TCMs.

Resveratrol (RES) is a natural polyphenol with potential as an adjunctive therapeutic modality for periodontitis. However, its inferior pharmacokinetics and toxicity concerns about its commonly used solvent dimethyl sulfoxide (DMSO) hinder translation to clinical applicability. Our study aimed to investigate the comparative antimicrobial properties of RES and its analogues (pterostilbene [PTS], oxyresveratrol [OXY] and piceatannol [PIC]), utilizing 2-hydroxypropyl-β-cyclodextrin (HPβCD) as a solubiliser, which has a well-documented safety profile and FDA approval. These properties were investigated against Fusobacterium nucleatum, a key periodontal pathogen. PTS demonstrated the most potent antibacterial effects in HPβCD, with MIC > 60-fold lower than that of RES, OXY and PIC. In addition, PTS inhibited F. nucleatum biofilm formation. PTS exerted antimicrobial effects by eliciting leakage of cellular contents, leading to loss of bacterial cell viability. PTS also conferred immunomodulatory effects on F. nucleatum-challenged macrophages via upregulation of antioxidant pathways and inhibition of NF-κB activation. Given the superior antimicrobial potency of PTS against F. nucleatum compared to RES and other analogues, and coupled with its immunomodulatory properties, PTS complexed with HPβCD holds promise as a candidate nutraceutical for the adjunctive treatment of periodontitis.

Severe malaria is potentially life-threatening and requires the parenteral administration of the artemisinin-based formulation for short duration of action. Intravenous artemether formulation has shown potentially better therapeutic efficacy but its poor aqueous dissolution constitutes a challenge. This work produced human serum albumin (HSA)-bound artemether nanoparticles by emulsification and desolvation approach using nanoparticle albumin bound (nab) technology for intravenous (IV) administration. The prepared nanoparticles had a size below 50 nm. It was observed that higher HSA concentration; lower drug concentration and longer ultrasonication time (up to 60 s) favoured the production of smaller particles. Comparatively, the emulsification method allowed for higher drug entrapment per the same concentration of HSA and required less organic solvent, less water and less energy and is therefore the preferred method. HSA-bound artemether nanoparticles displayed significantly enhanced dissolution properties over raw artemether. In-vitro haemolysis studies demonstrated a significant decrease in haemolysis caused by artemether from 101% to 7% in the emulsification product and to 4% by the desolvation product.

Apigenin trimethyl ether (5,7,4'-trimethoxyflavone, ATE) is a naturally occurring polymethoxyflavone with a wide range of health-promoting activities. In this study, a sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantification of ATE in rat plasma. Protein precipitation was applied as plasma clean-up procedure; the electrospray ionization was operated in its positive ion mode while ATE and formononetin (internal standard) were measured by multiple reactions monitoring (ATE: m/z 313.1→298.1; formononetin: 269.2→213.3). This LC-MS/MS method displayed good selectivity, sensitivity (lower limit of quantification=2.5ng/ml), accuracy (both intra- and inter-day analytical recovery within 100±10%) and precision (both intra- and inter-day RSD

Background and Purpose Chronic obstructive pulmonary disease (COPD) is a corticosteroid-resistant airway inflammatory condition. Resveratrol exhibits anti-inflammatory activities in COPD but has weak potency and poor pharmacokinetics. This study aimed to evaluate the potential of isorhapontigenin, another dietary polyphenol, as a novel anti-inflammatory agent for COPD by examining its effects in vitro and pharmacokinetics in vivo. Experimental Approach Primary human airway epithelial cells derived from healthy and COPD subjects, and A549 epithelial cells were incubated with isorhapontigenin or resveratrol and stimulated with IL-1β in the presence or absence of cigarette smoke extract. Effects of isorhapontigenin and resveratrol on the release of IL-6 and chemokine (C-X-C motif) ligand 8 (CXCL8), and the activation of NF-κB, activator protein-1 (AP-1), MAPKs and PI3K/Akt/FoxO3A pathways were determined and compared with those of dexamethasone. The pharmacokinetic profiles of isorhapontigenin, after i.v. or oral administration, were assessed in Sprague–Dawley rats. Key Results Isorhapontigenin concentration-dependently inhibited IL-6 and CXCL8 release, with IC50 values at least twofold lower than those of resveratrol. These were associated with reduced activation of NF-κB and AP-1 and, notably, the PI3K/Akt/FoxO3A pathway, that was relatively insensitive to dexamethasone. In vivo, isorhapontigenin was rapidly absorbed with abundant plasma levels after oral dosing. Its oral bioavailability was approximately 50% higher than resveratrol. Conclusions and Implications Isorhapontigenin, an orally bioavailable dietary polyphenol, displayed superior anti-inflammatory effects compared with resveratrol. Furthermore, it suppressed the PI3K/Akt pathway that is insensitive to corticosteroids. These favourable efficacy and pharmacokinetic properties support its further development as a novel anti-inflammatory agent for COPD.

Scope To evaluate the health-promoting potentials of piceatannol (PIC), a dietary resveratrol derivative, its biotransformation is examined. Methods and results The biotransformation is tested in human/rat hepatic microsomes and cytosols; its pharmacokinetic profiles are assessed in rats. Although limited phase I metabolism exists in microsomes, PIC is rapidly converted to two pharmacologically active metabolites, namely rhapontigenin (RHA) and isorhapontigenin (ISO) in cytosols. Such biotransformation is completely blocked by entacapone, a well-known catechol-O-methyltransferase (COMT) inhibitor, demonstrating that the O-methylation is mediated by COMT. Moreover, PIC is identified as a substrate inhibitor of COMT, suggesting its potential benefits in Alzheimer's disease. Due to extensive phase II metabolism including glucuronidation, sulfation, and O-methylation, PIC displays rapid clearance and at least 4.02% ± 0.61% and 17.70% ± 0.91% of PIC is converted to RHA and ISO, respectively, in rats after intravenous administration. Similarly, PIC serves as an effective precursor of ISO upon oral administration. Conclusion Since PIC and its metabolites possess pleiotropic health-promoting activities, it has emerged as a promising nutraceutical candidate for further development. This study also reinforces the importance of in vivo testing in nutritional researches as the active metabolite(s) may be absent from the in vitro system.

Methimazole (MMI) has been used in the therapy of Grave's disease (GD) since 1954, and drug-induced liver injury (DILI) is one of the most deleterious side effects. Genetic polymorphisms of drug-metabolizing enzymes and drug transporters have been associated with drug-induced hepatotoxicity in many cases. The aim of this study was to investigate genetic susceptibility of the drug-metabolizing enzymes and drug transporters to the MMI-DILI. A total of 44 GD patients with MMI-DILI and 118 GD patients without MMI-DILI development were included in the study. Thirty-three single nucleotide polymorphisms (SNPs) in twenty candidate genes were genotyped. We found that rs12422149 of SLCO2B1, rs2032582_AT of ABCB1, rs2306283 of SLCO1B1 and rs4148323 of UGT1A1 exhibited a significant association with MMI-DILI; however, no significant difference existed after Bonferroni correction. Haplotype analysis showed that the frequency of SLCO1B1*1a (388A521T) was significantly higher in MMI-DILI cases than that in the control group (OR = 2.21, 95% CI = 1.11-4.39, P = 0.023), while the frequency of SLCO1B1*1b (388G521T) was significantly higher in the control group (OR = 0.52, 95% CI = 0.29-0.93, P = 0.028). These results suggested that genetic polymorphisms of SLCO1B1 were associated with susceptibility to MMI-DILI. The genetic polymorphism of SLCO1B1 may be important predisposing factors for MMI-induced hepatotoxicity.

Wuzhi capsule (WZC) is commonly prescribed with tacrolimus in China to ease drug-induced hepatotoxicity. Two abundant active ingredients, schisantherin A (STA) and schisandrin A (SIA) are known to inhibit CYP3A enzymes and increase tacrolimus’s exposure. Our previous study has quantitatively demonstrated the contribution of STA and SIA to tacrolimus pharmacokinetics based on physiologically-based pharmacokinetic (PBPK) modeling. In the current work, we performed reversible inhibition (RI) and time-dependent inhibition (TDI) assays with CYP3A5 genotyped human liver microsomes (HLMs), and further integrated the acquired parameters into the PBPK model to predict the drug–drug interaction (DDI) in patients with different CYP3A5 alleles. The results indicated STA was a time-dependent and reversible inhibitor of CYP3A4 while only a reversible inhibitor of CYP3A5, SIA inhibited CYP3A4 and 3A5 in a time-dependent manner but also reversibly inhibited CYP3A5. The predicted fold-increases of tacrolimus exposure were 2.70 and 2.41, respectively, after the multidose simulations of STA. SIA also increased tacrolimus’s exposure but to a smaller extent compared to STA. An optimized physiologically-based pharmacokinetic (PBPK) model integrated with CYP3A5 polymorphism was successfully established, providing more insights regarding the long-term DDI between tacrolimus and Wuzhi capsules in patients with different CYP3A5 genotypes.

To evaluate the potential of oxyresveratrol (OXY), a dietary polyphenol with various health-promoting activities as a nutraceutical/functional food ingredient, its absolute oral bioavailability ( F ) was examined in Sprague-Dawley rats. Upon single intravenous administration (15 µmol/kg), rapid clearance ( Cl ) and short mean transit time ( MTT ) was observed. Dose-escalation to 90 µmol/kg did not alter its Cl and MTT significantly. After single oral administration (100 µmol/kg), although its F was only ~10%, OXY was absorbed rapidly and displayed long residence in systemic circulation. Dose-escalation to 400 µmol/kg brought ~60% and 100% increase in F and dose-normalized maximal plasma concentration ( C max ), respectively. One-week daily dosing (100 µmol/kg) did not cause substantial change in F and C max . Although OXY possessed slower Cl , its oral plasma exposure was comparable to RES. As OXY was orally bioavailable, further development of OXY as a nutraceutical/functional food ingredient is warranted.

Pinostilbene (3-methoxyresveratrol or trans-3,4'-dihydroxy-5-methoxystilbene) is a naturally occurring monomethylether analogue of resveratrol (trans-3,5,4'-trihydroxystilbene) that exhibits various pharmacological activities. To further examine its medicinal potential, a sensitive LC-MS/MS method was developed and validated for the determination of pinostilbene in rat plasma. Heavy Isotope labelled resveratrol was used as an internal standard. The ESI was operated in its negative ion mode while pinostilbene and resveratrol were measured by multiple reaction monitoring (MRM) using precursor-to-product ion transitions of m/z 241→181 and m/z 233→191, respectively. This LC-MS/MS method had excellent selectivity, sensitivity (LLOQ=1ng/ml), accuracy (both intra- and interday analytical recovery within 100±15%) and precision (both intra- and interday RSD < 15%). The matrix effect was insignificant. The pharmacokinetics of pinostilbene was subsequently profiled in Sprague-Dawley rats. Upon intravenous administration (5 or 10mg/kg), pinostilbene displayed rapid clearance (Cl=129±42 or 107±31ml/min/kg) and extremely short mean transit time (MTT=6.24±0.41 or 8.52±1.38min). After oral dosing (50mg/kg), the bioavailability of pinostilbene was limited but highly erratic (F=1.87±2.67%). Pharmacokinetic comparison among pinostilbene, resveratrol and some resveratrol analogues suggested that stilbenes with meta-hydroxyl group(s) may be associated with metabolic instability and subsequently suffer from rapid clearance and low oral bioavailability. The information obtained from this study will facilitate further exploration on pinostilbene as well as other resveratrol analogues.

Plasma protein binding (PPB) is a key player of drug ADME (absorption, distribution, metabolism, elimination) behaviors, enabling PPB to have significant impact on drug efficacy and toxicity. As drug discovery enters the era of rational drug design, it is desirable to use in silico model to predict PPB so as to achieve rapid initial screening for potential candidate compounds prior to further time-consuming and costly in vitro and in vivo experimental assay. In this study, a global quantitative structure-activity relationship (QSAR) model of PPB was built on the basis of a large training set comprising more than 5000 compounds to represent large structural diversity. The uneven distribution of PPB was often rectified by two mathematical transformations of PPB but this led to a decrease in prediction accuracy at the lower binding level. To resolve this problem, we proposed a novel strategy to build models for different binding levels. The best model yielded much lower mean absolute error (MAE) of 0.076 on the test set than published models and the MAE was further reduced to 0.041 ​at the high level of binding (0.8–1). The models also performed excellent in the validation set containing some compounds from traditional Chinese medicine. In addition, the applicability domain was determined to identify new compounds which are appropriate for prediction using our built models. In conclusion, this study developed a novel strategy to construct robust QSAR model for PPB prediction which could be used by chemists to predict the PPB of candidate compounds efficiently and make structural modification in the early stage of drug development.

Apigenin trimethyl ether (5,7,4′-trimethoxyflavone, ATE), one of the key polymethoxyflavones present in black ginger (rhizome of Kaempferia parviflora) possesses various health-promoting activities. To optimize its medicinal application, the pharmacokinetics of ATE was assessed in Sprague-Dawley rats with emphases to identify the impacts from dose and repeated dosing on its major pharmacokinetic parameters. Plasma ATE levels were monitored by liquid chromatography–tandem mass spectrometry (LC–MS/MS) method. Upon single intravenous administration (2 mg/kg), plasma levels of ATE declined through an apparent first-order process while dose-escalation to 4 and 8 mg/kg led to its non-linear disposition, which could be described by the Michaelis-Menten model. Similarly, dose-dependent oral pharmacokinetics was confirmed and when the dose was escalated from 5 to 15 and 45 mg/kg, much longer mean residence time (MRT0→last), higher dose-normalized maximal plasma concentration (Cmax/Dose) and exposure (AUC/Dose) were observed at 15 and/or 45 mg/kg. One-week daily oral administration of ATE at 15 mg/kg caused its accelerated elimination and the plasma exposure (AUC) after intravenous (2 mg/kg) and oral administration (15 mg/kg) dropped ~40 and 60%, respectively. As ATE displayed both dose- and time-dependent pharmacokinetics, caution is needed in the medicinal applications of ATE and/or black ginger.

The metabolism of a promising antineoplastic agent, trans-2,6-difluoro-4′-(N,N-dimethylamino)stilbene (DFS), was studied in mouse, rat, and human liver microsomes using liquid chromatography-tandem mass spectrometry (LC-MS/MS) with the multiple reaction monitoring-information-dependent acquisition-enhanced product ion scan (MRM-IDA-EPI) method. Ten putative metabolites were identified and the structures of four metabolites were confirmed using authentic standards. Since trans-2,6-difluoro-4′-(N-methylamino)stilbene (DMDFS, M1) was present in all species as metabolite and displayed in vitro growth inhibition superior to DFS, its pharmacokinetic profiles were examined in Sprague–Dawley rats using DFS as a comparator. A reliable LC-MS/MS multiple reaction monitoring (MRM) method was subsequently developed and validated for the simultaneous quantification of both DFS and DMDFS in rat plasma for this purpose. Upon intravenous administration (4 mg/kg), DFS had a moderate clearance (Cl = 62.7 ± 23.2 mL/min/kg), terminal elimination half-life (t 1/2 λZ = 299 ± 73 min), and mean transit time (MTT = 123 ± 14 min) with demethylation metabolism accounting for about 10 % of its total clearance. DMDFS possessed an intravenous pharmacokinetic profile similar to DFS. During oral dosing (10 mg/kg) where both DFS and DMDFS were absorbed rapidly, the oral bioavailability of DFS was approximately 2-fold greater than that of DMDFS (DFS: F = 42.1 ± 12.8 %; DMDFS: F = 18.7 ± 3.9 %). Interestingly, the DMDFS exposure after oral dosing of DFS (10 mg/kg) was comparable to that after oral administration of DMDFS (10 mg/kg) alone. As DFS displayed potent anticancer activities and excellent pharmacokinetic profiles, it appears to be a favorable candidate for further pharmaceutical development.

Desoxyrhapontigenin (DRG, 4-methoxyresveratrol or trans-3,5-dihydroxy-4'-methoxystilbene) is a naturally occurring resveratrol (RES) derivative with a variety of biological activities. To facilitate its further medicinal exploration, a reliable LC-MS/MS method was developed and validated for the quantification of DRG in rat plasma using heavy isotope labelled RES as an internal standard. The ESI was operated in its negative ion mode while DRG and RES were determined by multiple reaction monitoring (MRM) using precursor-to-product ion transitions of m/z 241.1 → 180.8 and m/z 233.0 → 191.0, respectively. This LC-MS/MS method displayed excellent selectivity, sensitivity (LLOQ = 2.5 ng/ml), accuracy (both intra- and interday mean analytical recovery within 100 ± 15%) and precision (both intra- and interday CV 15%). The mean matrix factors were all within 1.000 ± 0.150 with CV 15%. The pharmacokinetic profiles of DRG were subsequently examined in Sprague-Dawley rats. Upon intravenous administration (4 or 10 mg/kg), DRG displayed very rapid clearance (Cl = 338 ± 66 or 275 ± 30 ml/min/kg) and short mean residence time (MRT = 12.9 ± 4.7 or 10.4 ± 0.5 min). After oral administration of DRG fully solubilized by 2-hydroxypropyl-β-cyclodextrin (HP-β-CD), the plasma profiles of DRG were highly erratic with a low absolute bioavailability (F 9.83 ± 5.31%). When DRG was given at a higher dose (50 mg/kg) in suspension form, the F was increased to 24.1 ± 5.6%. The pharmacokinetic comparison among DRG, RES and some of its hydroxyl analogues stilbenes was performed. The information obtained from this study will facilitate further exploration on DRG as well as other RES derivatives.

Schisantherin A and schisandrin A, the most abundant active ingredients of Wuzhi capsule, are known to inhibit tacrolimus metabolism by inhibiting CYP3A4/5. We aimed to predict the contribution of schisantherin A and schisandrin A to drug-drug interaction (DDI) between Wuzhi capsule and tacrolimus using physiologically-based pharmacokinetic (PBPK) modelling. Firstly, the inhibition mechanism of schisantherin A and schisandrin A on CYP3A4/5 was investigated. Thereafter, PBPK models of schisantherin A, schisandrin A and tacrolimus were established. Finally, tacrolimus pharmacokinetics were evaluated after the combined use with schisantherin A or schisandrin A. The blood area under the curve (AUC) of tacrolimus increased 1.77- and 2.61-fold after a single dose and multiple doses of schisantherin A, respectively. Meanwhile, schisandrin A inhibited tacrolimus metabolism to a smaller extent. Also, it showed that mechanism-based inhibition (MBI) played a more important role in DDI than reversible inhibition after long-term administration, while reversible inhibition was comparable to MBI after single-dose administration. In conclusion, we utilized PBPK modelling to quantify the contribution of schisantherin A and schisandrin A to DDI between tacrolimus and Wuzhi capsule. This may provide more insights for the rational use of this drug combination.

This study aimed to evaluate the suitability of pterostilbene for anti-inflammatory application. The in vitro anti-inflammatory activities of pterostilbene were assessed using resveratrol, piceatannol and resveratrol trimethyl ether as comparators while its pharmacokinetics was examined in rats. All tested compounds displayed concentration-dependent anti-proliferative effect in E11 human rheumatoid arthritic synovial fibroblasts. They also suppressed LPS-induced NF-κB p65 nuclear translocation, down-regulated the secretions of IL-6, IL-18, VEGF, nitric oxide, MMP-2 and MMP-9 in E11 cells and attenuated E11-driven migration of THP-1 and U937 monocytes. Similarly, they inhibited LPS-induced pro-inflammatory cytokines in THP-1 cells. Interestingly, pterostilbene usually displayed in vitro anti-inflammatory potencies stronger than resveratrol. In vivo studies revealed that pterostilbene was extensively distributed to major drug target organs like liver, kidney, heart, lung as well as brain and repeated oral dosing did not significantly alter its pharmacokinetics. In conclusion, pterostilbene appears to be a promising candidate for further development.

Atorvastatin and its lactone form metabolite are reported to be associated with statin-induced myopathy (SIM) such as myalgia and life-threatening rhabdomyolysis. Though the statin-induced rhabdomyolysis is not common during statin therapy, its incidence will significantly increase due to pharmacokinetic drug-drug interactions (DDIs) with inhibitor drugs which inhibit atorvastatin’s and its lactone’s metabolism and hepatic uptake. Thus, the quantitative analysis of DDIs of atorvastatin and its lactone with cytochrome P450 3A4 (CYP3A4) and organic anion-transporting polypeptide (OATP) inhibitors is of great importance. This study aimed to predict pharmacokinetic DDIs possibly causing atorvastatin-induced rhabdomyolysis using Physiologically Based Pharmacokinetic (PBPK) Modelling. Firstly, we refined the PBPK models of atorvastatin and atorvastatin lactone for predicting the DDIs with CYP3A4 and OATP inhibitors. Thereafter, we predicted the exposure changes of atorvastatin and atorvastatin lactone originating from the case reports of atorvastatin-induced rhabdomyolysis using the refined models. The simulation results show that pharmacokinetic DDIs of atorvastatin and its lactone with fluconazole, palbociclib diltiazem and cyclosporine are significant. Consequently, clinicians should be aware of necessary dose adjustment of atorvastatin being used with these four inhibitor drugs.

Pinosylvin (trans-3,5-dihydroxystilbene), a naturally occurring analogue of resveratrol (trans-3,5,4'-trihydoxystilbene), exhibited various beneficial pharmacological activities in pre-clinical studies. To further probe its potential medicinal application, a sensitive liquid chromatography-tandem mass spectrometry method (LC-MS/MS) was developed and validated for the quantification of pinosylvin in rat plasma. A simple protein precipitation procedure was used for plasma cleanup before analysis by LC-MS/MS with electrospray ionisation and multiple reaction monitoring in its negative ion mode. This LC-MS/MS method demonstrated good selectivity, accuracy (intra- and inter-day analytical recovery within 100±7.7%), precision (intra- and inter-day coefficient of variation12.0%) and sensitivity (lower limit of detection=1.0ng/mL), with excellent linearity (R(2)0.99) over the range of 1-1000ng/mL. The pharmacokinetic profiles of pinosylvin were subsequently assessed in Sprague-Dawley rats. Following intravenous administration (5 or 10mg/kg), plasma levels of pinosylvin declined rapidly with a short half-life (t1/210min). Upon oral administration at 15mg/kg, pinosylvin could not be quantified in plasma (1ng/mL) while dose-escalation to 50mg/kg led to a low and erratic plasma exposure with very poor estimated oral bioavailability (F1%). The short half-life and limited systemic exposure of pinosylvin prompt caution in its therapeutic application and it warrants exploration in developing pinosylvin pro-drug.

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.

Chronic obstructive pulmonary disease (COPD) is a corticosteroid-resistant airway inflammatory condition. Resveratrol exhibits anti-inflammatory activities in COPD but has weak potency and poor pharmacokinetics. This study aimed to evaluate the potential of isorhapontigenin, another dietary polyphenol, as a novel anti-inflammatory agent for COPD by examining its effects in vitro and pharmacokinetics in vivo.Primary human airway epithelial cells derived from healthy and COPD subjects, and A549 epithelial cells were incubated with isorhapontigenin or resveratrol and stimulated with IL-1β in the presence or absence of cigarette smoke extract. Effects of isorhapontigenin and resveratrol on the release of IL-6 and chemokine (C-X-C motif) ligand 8 (CXCL8), and the activation of NF-κB, activator protein-1 (AP-1), MAPKs and PI3K/Akt/FoxO3A pathways were determined and compared with those of dexamethasone. The pharmacokinetic profiles of isorhapontigenin, after i.v. or oral administration, were assessed in Sprague-Dawley rats.Isorhapontigenin concentration-dependently inhibited IL-6 and CXCL8 release, with ICIsorhapontigenin, an orally bioavailable dietary polyphenol, displayed superior anti-inflammatory effects compared with resveratrol. Furthermore, it suppressed the PI3K/Akt pathway that is insensitive to corticosteroids. These favourable efficacy and pharmacokinetic properties support its further development as a novel anti-inflammatory agent for COPD.

Ginsenoside Rh4 (Rh4) and ginsenoside Rk3 (Rk3) are two active substances isolated from the processed Panax species. To further explore their potential medicinal application, a reliable liquid chromatography-tandem mass spectrometry method (LC/MS/MS) was developed and validated for the quantification of Rh4 and Rk3 in rat plasma. Multiple ion monitoring and multiple reaction monitoring experiments were performed in negative ionization mode. This LC/MS/MS method had good selectivity, sensitivity (lower limit of quantification = 10 ng/mL), precision (intra- and inter-day relative standard deviation ≤ 10.1) and accuracy (analytical recovery within 100 ± 10%). The pharmacokinetic profiles of Rh4 and Rk3 were subsequently assessed in Sprague-Dawley rats. Similar to many other ginsenosides, the oral bioavailability of Rh4 and Rk3 was unfavorable, and Rh4 and Rk3 did not have any measurable plasma exposure after oral administration (20 mg/kg). Fortunately, upon intravenous administration (5 mg/kg), both Rh4 and Rk3 possessed abundant plasma exposure, moderate clearance (Cl = 50.2 ± 7.7 and 23.8 ± 1.4 mL·min(-1)·kg(-1), respectively) and terminal elimination half-life (t(1/2 λZ) = 157.2 ± 65.2 and 99.5 ± 37.8 min, respectively). As Rh4 and Rk3 displayed favorable intravenous pharmacokinetic profiles, further exploration on their medicinal application is warranted.

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.

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

Summary Background: Vorinostat (suberoylanilide hydroxamic acid) is the first histone deacetylase inhibitor approved by US FDA for use in oncology. However, as a hydrophobic acid, its limited aqueous solubility poses a problem for parenteral delivery. Such limited solubility may also affect its oral bioavailability. Objective: The aim of this study was to evaluate whether cyclodextrins (CDs), common excipients used in pharmaceutical industry, could increase the aqueous solubility of vorinostat. Methods: The actual aqueous solubility of vorinostat was investigated by phase-solubility method. Molecular simulation was employed to predict the interaction energy and preferred orientation of vorinostat in CD cavities. Results: Phase-solubility studies indicated that the solubility of vorinostat (7·24 × 10−1 mm) was substantially increased when complexed with various CDs, in the following order: randomly methylated-β-cyclodextrin (RM-β-CD) > hydroxypropyl-β-cyclodextrin (HP-β-CD) > α-cyclodextrin > hydroxypropyl-α-cyclodextrin > Hydroxypropyl-γ-cyclodextrin > γ-cyclodextrin. RM-β-CD 300 mm increased vorinostat solubility to 70·8 mm, almost two orders of magnitude higher than the baseline solubility. Such findings were in good agreement with the results obtained from molecular simulation. Conclusion: CDs, particularly RM-β-CD and HP-β-CD, increased vorinostat’s solubility. Future studies could be focused on the application of HP-β-CD in parenteral delivery of vorinostat or using RM-β-CD as an oral absorption enhancer. Molecular simulation appeared to be a useful tool for the selection of appropriate CD as excipient for drug delivery.

A simple LC method has been developed and validated to determine trans-3,5,3′,4′,5′-pentamethoxystilbene (PMS) in rat plasma. Chromatographic separation was achieved through gradient delivery of acetonitrile and water (1.5 mL min−1) at 50 °C. PMS was quantified using UV detection at 320 nm. The standard curve ranged from 15 to 1,500 ng mL−1. The intra- and inter-day precisions, in terms of CV, were all less than 10% while the inter-day and intra-day bias ranged from −6.8 to 8.3%. The plasma PMS levels were monitored in Sprague-Dawley rats after drug administration. This simple LC method appears to be useful in the pharmacokinetic investigation of PMS.

Objectives. MS-275 and suberoylanilide hydroxamic acid (SAHA) are histone deacetylase (HDAC) inhibitors currently tested in oncology trials. They have also been found to display potent anti-rheumatic activities in rodent models for RA. However, the anti-rheumatic mechanisms of action remain unknown. The study was carried out with the intent of determining the anti-inflammatory and anti-rheumatic mechanisms of the HDAC inhibitors. Methods. In this study, the anti-rheumatic mechanisms of MS-275 and SAHA were investigated in several cell culture models. Results. MS-275 and SAHA inhibited human RA synovial fibroblastic E11 cell proliferation in a noncytotoxic manner. The anti-proliferative activities were associated with G0/G1 phase arrest and induction of cyclin-dependent kinase inhibitor p21. In addition, MS-275 and SAHA suppressed lipopolysaccharide (LPS)-induced NF-kB p65 nuclear accumulation, IL-6, IL-18 and nitric oxide (NO) secretion as well as down-regulated pro-angiogenic VEGF and MMP-2 and MMP-9 production in E11 cells at sub-micromolar levels. At similar concentrations, MS-275 and SAHA suppressed LPS-induced NF-kB p65 nuclear accumulation and IL-1b, IL-6, IL-18 and TNF-a secretion in THP-1 monocytic cells. Moreover, NO secretion in RAW264.7 macrophage cells was also inhibited. Conclusions. In summary, MS-275 and SAHA exhibited their anti-rheumatic activities by growth arrest in RA synovial fibroblasts, inhibition of pro-inflammatory cytokines and NO, as well as down-regulation in angiogenesis and MMPs. Their anti-rheumatic activities may be mediated through induction of p21 and suppression of NF-kB nuclear accumulation.

A rapid HPLC-UV method had been developed and validated to quantify 3,5,4'-trimethoxy-trans-stilbene (TMS), a naturally occurring and pharmacologically active analog of resveratrol in rat plasma. The samples were mixed with three volumes of acetonitrile to precipitate protein. Chromatographic separation was achieved on a RP-HPLC column (Agilent ZORBAX Eclipse Plus C18: 250 mm x 4.6mm i.d., 5microm), which was protected by a guard column (Agilent ZORBAX Eclipse Plus C18: 12.5 mm x 4.6mm i.d., 5microm) through isocratic delivery of a mobile phase of acetonitrile: water (75:25, v/v) at a flow rate of 1.2ml/min. The assay was executed at 30 degrees C and the UV absorbance at 320nm was monitored. The retention time of TMS and trans-stilbene (internal standard) was 6.5 and 8.3min, respectively. The calibration curve was linear within the range of 15-1000ng/ml (R(2)>0.998) and 15ng/ml was the lower LOQ. The intra- and inter-day precisions were good and the RSD was all lower than 7.3%. The mean absolute recovery of TMS in plasma ranged from 99.2 to 104.1%. This HPLC method had been successfully applied to study the pharmacokinetics of TMS, which was fully dissolved with hydroxypropyl-beta-cyclodextrin (HP-beta-CyD). In comparison with resveratrol, TMS had greater plasma exposure, longer elimination half-life and lower clearance. As TMS had superior pharmacokinetic characteristics, its potential as a preventive or therapeutic agent in resveratrol-effective conditions or diseases should be considered.

13- cis -Retinoic acid (13- cis -RA), also known as isotretinoin, is commonly used in the management of severe acne. Its clinical efficacy in oncology has also been documented. As a vitamin A derivative, it is not soluble in water. This solubility barrier not only affects its oral absorption but also makes parenteral delivery difficult. Recently, water-soluble formulations of 13- cis -RA have been attempted with 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) and randomly methylated-β-cyclodextrin (RM-β-CD). In this study, the pharmacokinetic profiles of these two formulations were assessed in Sprague–Dawley rats after single intravenous or oral administration. We found that 13- cis -RA was eliminated from the body through a dose-independent process after intravenous injection of either sodium salt or the HP-β-CD formulation within the tested dosage range (2.0–7.5 mg/kg). Furthermore, HP-β-CD did not alter the kinetic profile of 13- cis -RA after intravenous administration in comparison with 13- cis -RA sodium salt. We also found that RM-β-CD dramatically enhanced the oral absorption of 13- cis -RA. At 10.0 mg/kg, the bioavailability of 13- cis -RA formulated with RM-β-CD was about three-fold higher than that of the control (13- cis -RA suspended in 0.5% carboxymethylcellulose (CMC)). Similarly, the oral absorption of 13- cis -RA was not saturated within our tested range (2.5–10.0 mg/kg) and the bioavailability remained unchanged. These results demonstrated that HP-β-CD and RM-β-CD were suitable excipients for the delivery of 13- cis -RA.

Evaluation of: Huber LC, Brock M, Hemmatazad H et al.: Histone deacetylase/acetylase activity in total synovial tissue derived from rheumatoid arthritis and osteoarthritis patients. Arthritis Rheum. 56(4), 1087–1093 (2007). Reduced activity of histone deacetylase (HDAC) was observed in both rheumatoid arthritis (RA) and osteoarthritis (OA). This was the first study that disclosed aberrant epigenetics in RA and OA. However, with limited sample size, such interesting findings need to be confirmed in a larger cohort of patients. HDAC inhibitors appear to be a therapeutic strategy for RA although they may not alter the disease progression of OA. Therefore, reduced HDAC activity might not contribute to the pathogenesis of RA and OA. As HDAC inhibitors were originally designed for oncological indications, they might not be well tolerated in long-term RA therapy. Thus, it is important to discover the molecular therapeutic mechanisms of HDAC inhibitors in RA. This is in the hope that, with a better understanding ...

Background and purpose: Rheumatoid arthritis (RA) is a chronic inflammatory disease. Histone deacetylase inhibitors (HDACi), a new class of anti-cancer agents, have recently been reported to exhibit potent anti-inflammatory activities. A proof of concept study was carried out with suberoylanilide hydroxamic acid (SAHA) and MS-275, two HDACi currently undergoing clinical investigations for various oncological indications.

trans-4,4′-Dihydroxystilbene (DHS) is a naturally occurring resveratrol analog that displayed promising anti-cancer activities in pre-clinical studies. To further probe its therapeutic potential, a sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the measurement of DHS in rat plasma using electrospray ionization and multiple reaction monitoring in its negative ion mode. This analytical method demonstrated excellent linearity (R 2 > 0.99), selectivity, sensitivity (with a lower limit of quantification of 2.0 ng/mL), accuracy (both intra- and inter-day analytical recovery within 100 ± 15 %) and precision (both intra- and inter-day relative standard deviation within 10 %). The pharmacokinetic profiles of DHS were subsequently assessed in Sprague–Dawley rats. Following intravenous injection (4 mg/kg), DHS had a moderate apparent volume of distribution of the central compartment (V c = 887 ± 297 mL/kg), clearance (Cl = 44.7 ± 5.1 mL/min/kg) and a relatively short mean transit time (MTT = 24.1 ± 8.8 min). When it was given as an oral suspension (10 mg/kg), DHS was absorbed slowly (t max 180 or 300 min) with very limited plasma exposure and absolute oral bioavailability (F = 2.22 ± 0.72 %). On the other hand, when DHS was fully solubilized by hydroxypropyl-β-cyclodextrin, it was absorbed rapidly (t max 30 or 45 min) with more than 15-fold increase in maximal plasma concentration (C max), plasma exposure (AUC 0→last) and bioavailability (F = 36.3 ± 4.8 %). Statistical comparison provided clear evidence that DHS was better than resveratrol from the perspective of pharmacokinetics. In conclusion, further explorations of DHS as an anti-cancer agent are warranted.

The natural mineral orpiment (As2S3) has long been used in traditional medicines for various diseases, although it is poorly soluble and has resulting low bioavailability. In this study, orpiment quantum dots (QDs) belonging to rare V–VI binary QDs were first synthesised through top-down and bottom-up routes, in which a mixture of ethanolamine and triethanolamine was used as a coordinating solvent. The as-synthesised orpiment QDs have a narrow size distribution, superior solubility, strong blue photoluminescence emission, and good stability. Preliminary in vitro cytotoxicity studies show that orpiment QDs are less cytotoxic for human normal dermal fibroblast cells but more potent against murine melanoma B16 cells through induction of apoptosis. Moreover, self-assemblies of orpiment QDs were fabricated through destroying the protective surface ligand layer surrounding the inner orpiment cores by addition of an acid. The underlying driving force is probably competitive reactions between the surface amine ligand and the introduced acid, leading to the exposure of the bare inner orpiment cores with high surface energy.

trans-2,3-Dimethoxystilbene (2,3-DMS) and trans-3,4-dimethoxystilbene (3,4-DMS) are two synthetic resveratrol (trans-3,5,4'-trihydroxystilbene) analogs. In this study, a simple HPLC method was developed and validated to determine 2,3-DMS and 3,4-DMS in rat plasma. Chromatographic separation was obtained with a reversed-phase HPLC column through a 12.5-min gradient delivery of a mixture of acetonitrile and water at the flow rate of 1.5 mL/min at 50 °C. The lower limit of quantification was 10 ng/mL. After successful validation, the pharmacokinetic profiles of 2,3-DMS and 3,4-DMS were subsequently studied in Sprague-Dawley rats. Upon single intravenous administration (4 mg/kg), 2,3-DMS had a medium volume of distribution of the central compartment (Vc = 2.71 ± 0.51 L/kg), quite rapid clearance (Cl = 52.0 ± 7.0 mL/min/kg), moderate mean transit time (MTT0→last = 131.0 ± 4.5 min) but a fairly long terminal elimination half-life (t1/2 λZ = 288.9 ± 92.9 min). Interestingly, 3,4-DMS displayed a pharmacokinetic profile apparently distinct from 2,3-DMS and it had more extensive distribution (Vc = 5.58 ± 1.73 L/kg), faster clearance (Cl = 143.4 ± 40.5 mL/min/kg) and shorter residence (MTT0→last = 61.4 ± 27.1 min). Following single oral administration (10 mg/kg), 2,3-DMS had low and erratic plasma exposure (Cmax = 37.5 ± 23.7 ng/mL) and poor oral bioavailability (2.22% ± 2.13%) while the oral bioavailability of 3,4-DMS was even poorer than 2,3-DMS. Clearly, the location of the methoxy groups had a significant impact on the pharmacokinetics of resveratrol analogs. This study provided useful information for the design of resveratrol derivatives in future study.