In vitro Inhibitory Effects of Andrographis paniculata, Gynura procumbens, Ficus deltoidea, and Curcuma xanthorrhiza Extracts and Constituents on Human Liver Glucuronidation Activity

BACKGROUND Andrographis paniculata, Gynura procumbens, Ficus deltoidea and Curcuma xanthorrhiza are commonly consumed as herbal medicines. However their effects on human liver glucuronidation activity are not yet evaluated. OBJECTIVE In this study, we evaluate the inhibitory Effects of Andrographis paniculata, Gynura procumbens, Ficus deltoidea and Curcuma xanthorrhiza extracts and their constituents on human liver glucuronidation activity. MATERIALS AND METHODS Herbal extracts (aqueous, methanolic and ethanolic extracts) and their constituents were incubated with human liver microsomes with the addition of UDPGA to initiate the reaction. Working concentrations of herbal extracts and their constituents ranged from 10 μg/mL to 1000 μg/mL and 10 μM to 300 μM respectively. IC50 was determined by monitoring the decrement of glucuronidation activity with the increment of herbal extracts or phytochemical constituent's concentrations. RESULTS All herbal extracts inhibited human liver glucuronidation activity in range of 34.69 μg/mL to 398.10 μg/mL whereas for the constituents, only xanthorrhizol and curcumin (constituents of Curcuma xanthorrhiza) inhibited human liver glucuronidation activity with IC50 of 538.50 and 32.26 μM respectively. CONCLUSION In the present study, we have proved the capabilities of Andrographis paniculata, Gynura procumbens, Ficus deltoidea and Curcuma xanthorrhiza to interfere with in vitro glucuronidation process in human liver microsomes. SUMMARY This study documented the capabilities of Andrographis paniculata, Gynura procumbens, Ficus deltoidea and Curcuma xanthorrhiza to inhibit human liver glucuronidation activity which may affect the metabolism of therapeutic drugs or hazardous toxicants that follow the same glucuronidation pathway. Abbreviations used: UGT: Uridine 5'-diphospho-glucuronosyltransferase; 4-MU: 4-methylumbelliferone; IC50: Half Maximal Inhibitory Concentration; Km: Michaelis constant; Vmax: Maximum velocity.