In vitro and in vivo effect of eurycoma longifolia root extract on UDP-glucuronosyltransferase activity

The aim of this research was to evaluate the effects of Eurycoma longifolia root extract (ELE) on enzymes activity in the phase II drug metabolism on Sprague-Dawley (SD) rats, especially on uridine 5'-diphospho-glucuronosyltransferase (UGT) activity, in vivo and in vitro. The UGT assay was performed as follows: for the in vivo study, the male SD rats were treated with ELE at doses ranging from 5 to 1,000 mg/kg b.w. and 5, 25, and 50 mg/kg b.w for acute and sub-acute study, respectively. The ELE concentrations of 0.01 to 1,000 μg/ml were used for in vitro study. The p-nitrophenol (pNP) that consumed in the glucuronidation process reflected the UGT activity and was calculated using standard curve of pNP. UGT enzyme activity was inhibited significantly (p < 0.01) by ELE extract in the male rat for both acute and sub-acute experiments. ELE extract decreased the enzyme activity significantly (p < 0.01), at all the concentrations tested in the in vitro experiment when compared to the negative control group. ELE had a lower activity (the IC50 of 0.74 μg/ml) as compared to Na diclofenac (positive control) with an IC50 of 0.17 μg/ml. Eurycoma longifolia decreased the UGT enzyme activity significantly (p < 0.01), both for in vivo and in vitro study.