Resveratrol Pretreatment Affects CYP2E1 Activity of Chlorzoxazone in Healthy Human Volunteers Satish Kumar Bedada and Prasad Neerati * Drug Metabolism and Clinical Pharmacokinetics Division, University College of Pharmaceutical Sciences, Kakatiya University, Warangal 506009, Telangana State, India The purpose of the present study was to investigate the effect of resveratrol (RSV) pretreatment on CYP2E1 enzyme activity and pharmacokinetics of chlorzoxazone (CHZ) in healthy human volunteers. The open-label, two period, sequential study was conducted in 12 healthy human volunteers. A single dose of RSV 500 mg was administered once daily for 10 days during treatment phase. A single dose of CHZ 250 mg was administered during control and after treatment phases under fasting conditions. The blood samples were collected after CHZ dosing at predetermined time intervals and analyzed by HPLC. RSV pretreatment significantly enhanced the maximum plasma concentration (C max ), area under the curve (AUC) and half life (T 1/2 ) and significantly decreased elimination rate constant (K el ), apparent oral clearance (CL/F) and apparent volume of distribution (Vd/F) of CHZ as compared to that of control. In addition, RSV pretreatment significantly decreased the metabolite to parent (6-OHCHZ/CHZ) ratios of C max , AUC and T 1/2 and significantly increased the K el ratio of 6-OHCHZ/ CHZ, which indicated the reduced formation of CHZ to 6-OHCHZ. The results suggest that the altered CYP2E1 enzyme activity and pharmacokinetics of CHZ might be attributed to RSV mediated inhibition of CYP2E1 enzyme. Thus, there is a potential pharmacokinetic interaction between RSV and CHZ. The inhibition of CYP2E1 by RSV may provide a novel approach for minimizing the hepatotoxicity of ethanol. Copyright © 2015 John Wiley & Sons, Ltd. Keywords: chlorzoxazone; resveratrol; CYP2E1 enzyme; pharmacokinetics; hepatotoxicity. INTRODUCTION Resveratrol (RSV) (3, 4′, 5-trihydroxystilbene) is a nat- urally occurring polyphenolic phytoalexin naturally present in fruits, vegetables, grape skins and especially in red wine. RSV possesses diverse biochemical and physiological properties including antiinflammatory, im- mune modulatory activities as well as wide range of health benefits ranging from chemoprevention to cardio protection (Kalantari and Das, 2010; Brisdelli et al., 2009). It is produced by these plants in response to stress, injury, ultraviolet irradiation and fungal infection as part of their defense mechanism, and it is synthesized by grapes in response to fungal infections and is found, therefore, in red wine at levels between 1 and 10 μM (Soleas et al., 1997). RSV modulates the synthesis of he- patic apolipoprotein and lipids and inhibits platelet ag- gregation and eicosanoid production in human platelets and neutrophils (Bertelli et al., 1996). More- over, RSV inhibits events associated with tumor initia- tion, promotion and progression (Jang et al., 1997). RSV has recently been shown to exert genoprotective, cytotoxic, antiproliferative and proapoptotic actions in different tumoural cell lines (Romano et al., 2013). It has been reported that RSV inhibited the activity of CYP2E1 enzyme in vitro in human liver microsomes (Piver et al., 2001). In addition, trans-resveratrol has been shown to inhibit CYP2E1 activity in vitro in mouse liver microsomes (Mikstacka et al., 2002). Further, it has been reported that pterostilbene (a natural analogue of trans-resveratrol) (Mikstacka et al., 2006) and epsilon- viniferin (a dimer of RSV) (Piver et al., 2003) were known to inhibit CYP2E1 activity in vitro. Previously it has been reported that RSV reduced the pyrogallol in- duced CYP2E1 activity in mice (Upadhyay et al., 2008). Furthermore, recently it has been suggested that RSV reduced the chemically induced hepatocarcinogenesis and the associated CYP2E1 activity in rats (Wu et al., 2013). Because RSV is a CYP2E1 inhibitor and may potentially inhibit CYP2E1 mediated metabolism which is responsible for the poor bioavailability of CYP2E1 substrates. Thus, the effect of RSV pretreatment on the pharmacokinetics of known CYP2E1 substrate, chlorzoxazone (CHZ), in healthy human volunteers is the subject of current investigation. CHZ is used as skeletal muscle relaxant to relieve muscular spasticity, a condition characterized by exag- gerated resting tone of a muscle. It is a centrally acting muscle relaxant and is a probe for CYP2E1 (Peter et al., 1990; Lucas et al., 1999). CHZ is almost exclusively metabolized by CYP2E1 to a single major metabolite, 6- hydroxychlorzoxazone (6-OHCHZ), which is rapidly glucuronidated and eliminated by the kidney (Desiraju et al., 1983). The CYP superfamilies of hemoproteins play a critical role in the metabolism of endogenous and exogenous compounds of diverse chemical struc- ture. In recent years, particular interest has been fo- cused on CYP2E1 because of its involvement in the * Correspondence to: Prasad Neerati, Drug Metabolism and Clinical Pharmacokinetics Division, University College of Pharmaceutical Sciences, Kakatiya University, Warangal 506009, Telangana State, India. E-mail: prasadneerati@outlook.com PHYTOTHERAPY RESEARCH Phytother. Res. 30: 463–468 (2016) Published online 17 December 2015 in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/ptr.5549 Copyright © 2015 John Wiley & Sons, Ltd. Received 24 June 2015 Revised 13 October 2015 Accepted 24 November 2015