title: Time-dependent inhibition of CYP3A4 by gallic acid in human liver microsomes and recombinant systems.
abstract: 1.Gallic acid is a main polyphenol in various fruits and plants. Inhibitory characteristics of gallic acid on CYP3A4 were still unclear. The objective of this work is hence to investigate inhibitory characteristics of gallic acid on CYP3A4 using testosterone as the probe substrate in human liver microsomes (HLMs) and recombinant CYP3A4 (rCYP3A4) systems. 2.Gallic acid caused concentration-dependent loss of CYP3A4 activity with IC50 values of 615.2 μM and 669.5 μM in HLM and rCYP3A4 systems, respectively. IC50-shift experiments showed that pre-incubation with gallic acid in the absence of NADPH contributed to 12- or 14-fold reduction of IC50 in HLM and rCYP3A4 systems, respectively, supporting a time-dependent inhibition. In HLM, time-dependent inactivation variables KI and Kinact were 485.8 μM and 0.05 min(-1), respectively. 3.Compared with the presence of NADPH, pre-incubation of gallic acid in the absence of NADPH markedly increased its inhibitory effects in HLM and rCYP3A4 systems. Those results indicate that CYP3A4 inactivation by gallic acid was independent on NADPH and was mainly mediated its oxidative products. 4.In conclusion, we showed that gallic acid weakly and time-dependently inactivated CYP3A4 via its oxidative products.
authors.affiliation: Institute of Life Science, Chongqing Medical University , Chongqing , P. R. China.
authors.forename: Qiang-Hong
authors.initials: QH
authors.lastname: Pu
authors.forename: Liang
authors.initials: L
authors.lastname: Shi
authors.forename: Chao
authors.initials: C
authors.lastname: Yu
mesh_terms: D051544:Cytochrome P-450 CYP3A / Q000378:metabolism*; D065607:Cytochrome P-450 Enzyme Inhibitors / Q000494:pharmacology*; D005707:Gallic Acid / Q000494:pharmacology*; D006801:Humans; D006900:Hydroxylation / Q000187:drug effects; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D009249:NADP / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism*; D013739:Testosterone / Q000378:metabolism; D013997:Time Factors
chemical_list: D065607:Cytochrome P-450 Enzyme Inhibitors; D011994:Recombinant Proteins; D013739:Testosterone; D009249:NADP; D005707:Gallic Acid; D051544:Cytochrome P-450 CYP3A
keywords: 6β-hydroxylase; CYP3A4; gallic acid; testosterone; time-dependent inhibition