In vitroeffects of rosmarinic acid on glutathione reductase and glucose 6-phosphate dehydrogenase

CONTEXT: Glutathione reductase (GR, NADPH:oxidized glutathione oxidoreductase, E.C 1.6.4.2) is a flavoprotein that catalyzes the NADPH-dependent reduction of oxidized glutathione (GSSG). GR is a crucial enzyme in the antioxidant system by maintaining reduced glutathione (GSH). Glucose 6-phosphate dehydrogenase (G6PD, glucose 6-phosphate (G6P):NADP(+) oxidoreductase, EC 1.1.1.49) is the key regulatory enzyme of the pentose phosphate pathway and maintains NADPH for reductive reactions. OBJECTIVE: Rosmarinic acid (RA; α-O-caffeoyl-3,4-dihydroxyphenyl lactic acid) is an ester of caffeic acid (CA) and 3,4-dihydroxyphenyllactic acid. It has a number of interesting biological activities. The inhibiting activities of the RA on GR and G6PD are investigated here for the first time. MATERIALS AND METHODS: GR and G6PD were purified from tissues, then the effects of RA are investigated. RESULTS: This study reports that RA, which was isolated from Echium vulgare L. (Boraginaceae), inhibits purified GR and G6PD in a concentration-dependent manner. Kinetic characterizations and inhibition constants are investigated. DISCUSSION AND CONCLUSION: Because of their importance in the antioxidative defense system, investigation of the inhibitors of these enzymes is important for drug development.