Antioxidant effect of astragalin isolated from the leaves of Morus alba L. against free radical-induced oxidative hemolysis of human red blood cells.

We evaluated the antioxidant properties of mulberry leaves extract (MLE) and flavonoids isolated from MLE. MLE was prepared by extraction with methanol. Flavonoids were analyzed by high-performance liquid chromatography. Oxidative hemolysis of normal human red blood cells (RBCs) was induced by the aqueous peroxyl radical [2,2'-Azobis (2-amidinopropane) dihydrochloride, AAPH]. MLE contained three flavonoids in the order quercetin (QC) > kaempferol (KF) > astragalin (AG). Oxidative hemolysis of RBCs induced by AAPH was suppressed by MLE, AG, KF, and QC in a time- and dose-dependent manner. MLE and these three flavonoids prevented the depletion of cystosolic antioxidant glutathione (GSH) in RBCs. AG had the greatest protective effect against AAPH-induced oxidative hemolysis and GSH depletion in RBCs.