Structure-effect study of quercetin and its Sugar-containing analogues as antioxidants in in vitro H2O2-induced cell injury model

Aim To determine effect of C-3 sugar group in molecule of flavonoids on their anti-free radical activity. Methods Three flavonoids: quercetin (Q) and its monoglycoside isoqurcetin (I), diglycoside rutin (R) were chosen as tool drugs and tested for their protective effects against H2O2-induced free-radical injury in in vitro incubated HEK293 cells. The cell survive rate (CSR) was measured by MTT method; TAC, SOD and LDH activities were determined by spectrophotometry. IC50 was calculated by means of linear regression equation of inhibitory rate (IR%) vs logarithmic drug concentration (logC) and used as an index to compare anti-free radical intensity among the 3 flavonoids. Results The pre-treatment of cells with Q, I, and R resulted in dose-dependently elevated CSR, SOD and TAC levels and lowered LDH level as compared with untreated cells with Q, I, and R. The IC50 values of 3 flavonoids were ranked as follows: IC50, Q I> R, indicating that increase in C-3 sugar group in molecule of flavonoids results in decreased anti-free radical activity and cyto-protective effect.