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.