Inhibitory Effects of Some Flavonoids on Thioredoxin Reductase Purified from Chicken Liver

ABSTRACT Thioredoxin reductases (TrxRs) are selenocysteine-containing flavoenzymes that reduce Trxin NADPH-dependent manner. In the view of the direct vital role of TrxR in a wide range of biochemical and physiological processes, methods to inhibit this enzyme are clinically important. TrxR has recently emerged as a new candidate in anticancer drug investigations because of overexpression in tumorous cells. In this study, TrxR from chick liver was purified 94.6-fold with a yield of 4.86% and a specific activity of 0.19 EU/mg. KM and Vmax values of TrxR for DTNB were calculated as 0.9 mM and 0,03 EU/mL, respectively. Then, the effects of the flavonoids hesperidin, naringenin, chlorogenic acid, ferulic acid, naringin, 3,4-dihydoxybenzoic acid, and ellagic acid on the enzyme activity were evaluated under in-vitro conditions. Ellagic acid showed the strongest inhibitory activity on TrxR with a IC50 value of 18 µM, followed by naringenin and chlorogenic acid with IC50 values of 46.7 µM and 75.8 µM, respectively. Our results showed that flavonoids as natural products are potential inhibitors of TrxRs and the flavonoid content in animal diets may alter metabolic pathways by influencing TrxR activity.