Karakurt, SerdarSever, MelikeÇelebioğlu, Hasan UfukAdalı, Orhan2020-03-262020-03-2620150250-46851303-829Xhttps://dx.doi.org/10.1515/tjb-2015-0010https://hdl.handle.net/20.500.12395/31813Objective: Glutathione S-transferase (GST) and NAD(P)H:quinine oxidoreductase 1 (NQO1) are the enzymes important in cytoprotection and bioactivation of chemicals. This study has addressed effects of polyphenolic compounds; ellagic acid, quercetin, naringenin, resveratrol, rutin and hesperidin on rabbit liver GST and NQO1 enzyme activities. Methods: Cytosolic fractions were obtained from homogenized liver tissues of rabbit by differential centrifugation. After calculating IC50 values of individual enzymes for phenolic compounds, both Lineweaver-Burk and Dixon plots were drawn to determine the effect of phenolics on enzyme activity. Michaelis-Menten constant (K-m), maximum velocity (V-max), and inhibition constant (K-i) were calculated from Lineweaver-Burk and Dixon plots, respectively. Results: Resveratrol was found to be the most potent inhibitor for rabbit hepatic cytosolic GST activity with 75.9 +/- 2.06 mu M IC50 value while naringenin was the least potent one with IC50 value of 260 +/- 1.92 mu M. Hesperidin and quercetin were found to be the most and least potent inhibitors for NQO1 enzyme activity with IC50 values of 2.7 +/- 0.85 mu M and 13.8 +/- 0.91 mu M, respectively. Resveratrol and naringenin inhibited GST activity noncompetitively and mixed type with K-i of 6.2 mu M and 245 mu M, respectively; while both hesperidin with 0.64 mu M K-i value and quercetin with 3.5 mu M K-i value inhibited NQO1 activity in a competitive manner. Conclusion: These results indicate that phenolic compounds may modulate Phase II enzyme, GST and NQO1. Moreover, they can influence the metabolic activation of xenobiotic and toxic compounds metabolized by this enzyme.en10.1515/tjb-2015-0010info:eu-repo/semantics/closedAccessGSTNQO1polyphenolsinhibition kineticIC50Article403251257Q4WOS:000358306700008Q4