In vitro UDP-Glucuronosyltransferase and Cytochrome P450 Enzymes Activities of Clinacanthus nutans Leaf Juice and Aqueous Extract

Aim: The objective of the present study was to evaluate the in vitro effect of aqueous extract of Clinacanthus nutans leaves and the juice on the activity of UDP-glucuronosyltransferase (UGT), cytochrome P (CYP) 3A4, and CYP2E1 in human liver microsomes (HLMs). Materials and Methods: The herb-drug interactions of the leaf extracts and juice were determined by a specific enzyme activity of CYP isoforms with specific probe substrate using spectrophotometry. CYP3A4 activity was measured for aminopyrine-specific metabolite (formaldehyde) at 415 nm. CYP2E1 activity was determined using p-nitrophenol-specific metabolite (p-nitrocatechol) at 535 nm. UGT activity was quantified through the consumption of p-nitrophenol by UGT at 405 nm. Results: Results obtained showed that the juice and aqueous extract of C. nutans leaves exhibited significant inhibition (P < 0.05) in CYP3A4 and CYP2E1 activity in HLMs. The aqueous extract of C. nutans showed statistically significant (P < 0.05) activation on UGT activity at the concentration of 1000 ng/mL as compared to the negative control. Conclusion: There is a possibility that herb-drug interaction could occur with C. nutans through inhibitory effects on CYP3A4 and CYP2E1. The leaf preparation also activated UGT catalyzed metabolism which may result in a reduction of the potency of the drug metabolized by UGT pathway.