Vol 11, Issue 9, 2018 Online - 2455-3891 Print - 0974-2441 EVALUATION OF THE CYTOCHROME P450 INHIBITORY EFFECT OF THYME OLEORESIN FROM THYMUS VULGARIS L. - AN IN VITRO STUDY ROY ANITHA*,ADELINE PERSIA R, THANGAVELU LAKSHMI Department of Pharmacology, Saveetha Dental College, Saveetha Institute of Medical and Technical Sciences, Saveetha University, Chennai, Tamil Nadu, India. Email: anitharoy2015@gmail.com Received: 18 April 2018, Revised and Accepted: 17 May 2018 ABSTRACT Objective: The objective of this study was to evaluate the effect of thyme oleoresin on cytochrome P450 (CYP3A4) enzyme. Materials and Methods: The different concentrations of thyme oleoresin (5–100 µg/ml) were examined for its inhibitory property toward cytochrome P450 isoform (CYP3A4). Thyme oleoresin, potassium phosphate buffer, CYP450 reagent, and substrate 7-Benzyloxy-4-trifluoromethylcoumarin were added to a 96-well plate. The mixtures were preincubated for 20 min at room temperature. The fluorescent intensities of the products were measured by PerkinElmer Enspire fluorescence reader using an excitation and emission wavelength of 405 nm and 460 nm, respectively. Values were expressed as mean ± standard error mean (n=3). IC 50 was calculated by plotting concentrations of thyme against the corresponding percent inhibition. Results: All the tested concentrations of thyme showed inhibitory effect against CYP3A4 in a dose-dependent manner. At 5 µg/ml, it showed a percentage inhibition of 1.82±0.61, whereas 100 µg/ml showed 66.05±0.16. The IC 50 value of thyme for CYP3A4 inhibitory activity was found to be 39.14 µg/ml. Conclusion: This study prove the inhibitory effect of thyme oleoresin on cytochrome P450. The inhibitory effect of thyme oleoresin indicates the possibilities of herb-drug interaction if this extract is co-administered with prescribed drugs that are metabolized by CYP3A4. Keywords: Thyme oleoresin, Cytochrome P450, Inhibitory assay, Thymus vulgaris. INTRODUCTION Plants are extensively explored to evaluate their antibacterial activity, antioxidant activity as well as their effect in various metabolic diseases and cancer. [1-4]. Oleoresins are composed of resins and essential oils obtained from herbs [5,6] and are rich in antioxidants [7-9]. They are extensively used in pharmaceutical and food industries [10-13]. In this study, thyme oleoresin from Thymus vulgaris L. was used for evaluating its effect on cytochrome P450 (CYP3A4). Cytochrome P450 is an important determinant in drug metabolism as well as in the occurrence of several drug interactions. These drug interactions can result in therapeutic failure, adverse drug reactions, and drug toxicities. Clinically, significant interactions can be prevented by identifying the drug involved as an enzyme substrate, inducer, or inhibitor and avoiding the coadministration of such drugs to get optimum response for the drugs [14]. Cytochrome P450 enzymes are primarily found in liver cells but are also located in cells throughout the body. Cytochrome P450 enzymes are located in endoplasmic reticulum and mitochondria. The enzymes found in mitochondria are generally involved in the synthesis and metabolism of internal substances, while enzymes in the endoplasmic reticulum usually metabolize external substances, primarily medications, and environmental pollutants. CYP3A4 isozymes are responsible for the extensive first-pass metabolism and inactivation of some drugs which are administered orally [15,16]. It is reported that, among the six isozymes of P450 such as CYP1A2, CYP2C19, CYP2C9, CYP2D6, CYP2E1, and CYP3A4, several clinically significant drug-drug interactions have resulted from CYP3A4 isozyme [17,18]. MATERIALS AND METHODS Plant material The thyme oleoresin from marigold flowers was obtained from Synthite Industries Private Limited, Kerala, as a gift sample. Chemicals CYP450 reagent, 7-Benzyloxy-4-trifluoromethylcoumarin (BFC), tris- HCl buffer and potassium phosphate buffer. All the chemicals used were of analytical grade. Inhibitory effect of cytochrome P450 enzyme activity (CYP3A4) About 5–100 µg/ml of the thyme oleoresin was used to evaluate the cytochrome P450 isoform CYP3A4 inhibitory effect. The various concentrations of thyme oleoresin, potassium phosphate buffer, CYP450 reagent, and substrate BFC were added to a 96-well plate. The mixtures were preincubated for 20 min at room temperature. The reaction was started by a mixture of free constituted substrate and NADP + and incubated at room temperature for 30–60 min. The reaction was stopped by tris-HCl buffer, pH 10.5. The fluorescent intensities of the products were measured by PerkinElmer Enspire fluorescence reader using an excitation and emission wavelength of 405 nm and 460 nm, respectively. IC 50 was calculated by plotting concentrations of thyme from 5 to 100 µg/ml against the corresponding percentage inhibition. [19]. RESULTS In this study, all the tested concentrations of thyme showed inhibitory effect against CYP3A4 in a dose-dependent manner. At 5 μg/ml, it showed a percentage inhibition of 1.82±0.61, whereas 100 μg/ml showed 66.05±0.16. The IC50 value for CYP3A4 inhibitory activity was found to be 39.14 μg/ml (Table 1). © 2018 The Authors. Published by Innovare Academic Sciences Pvt Ltd. This is an open access article under the CC BY license (http://creativecommons. org/licenses/by/4. 0/) DOI: http://dx.doi.org/10.22159/ajpcr.2018.v11i9.26759 Research Article