In-vitro inhibitory effect of Tualang honey on cytochrome P450 2C8 activity.

To investigate the effect of Tualang honey on cytochrome P450 2C8 (CYP2C8) activity in vitro using an amodiaquine N-desethylase assay. CYP2C8 and NADPH cytochrome P450 reductase was cotransformed, expressed and harvested. The incubation assay contained expressed proteins, MgCl(2), NADP, glucose 6-phosphate, glucose-6-phosphate dehydrogenase, potassium phosphate buffer, and amodiaquine. The rate of conversion of amodiaquine to desethylamodiaquine, the metabolite, was determined using a high performance liquid chromatography (HPLC) method. The inhibition parameters, IC50 (concentration of inhibitor causing 50% inhibition of original enzyme activity) and apparent inhibition constant (K(i) ) values were determined. The recombinant proteins were successfully expressed and used to investigate the effect of Tualang honey on CYP2C8 activity. The activity was measured by the rate of metabolism of amodiaquine to desethylamodiaquine determined using a successfully developed HPLC method. Kinetic parameters as determined by nonlinear least-squares regression and evaluated with Aikeike's goodness of fit criteria revealed that Tualang honey competitively inhibited CYP2C8 activity in a dose-dependent manner. Maximum inhibition of 80% occurred at 0.01% honey. The IC50 and K(i) values were (10.0 ± 3.0) × 10(-3) % and (5.1 ± 0.5) × 10(-3) % w/v, respectively. This study has provided evidence for the in vitro inhibition of CYP2C8-mediated amodiaquine N-desethylase activity by Tualang honey. It revealed that honey, through this inhibition, may have the potential to cause in-vivo drug-food interaction with drugs metabolized by CYP2C8.