Objective To further investigate the neuroprotective effects of five isoflavonoids from Astragalus mongholicus on xanthine (XA)/xanthine oxidase(XO)-induced injury to PC12 cells.Methods PC12 cells were damaged bv XA/XO.The activities of antioxidant enzymes,MTT,LDH,and GSH assays were used to evaluate the protection of these five isoflavonoids Contents of Bcl-2 family proteins were determined with flow cytometry.Results Among the five isoflavonoids including formononetin,ononin,9,10-dimethoxypterocarpan-3-O-β-D-glucoside,calycosin and calycosin-7-O-glucoside,calycosin and calycosin-7-O-glucoside were found to inhibit XA/XO-induced injury to PC12 cells.Their EC(50) values of formononetin and calycosin were 0.05μg/mL.Moreovet,treatment with these three isoflavonoids prevented a decrease in the activities of antioxidant enzymes,superoxide dismutase(SOD)and glutathione peroxidase(GSH-Px),while formononetin and calycosin could prevent a significant deletion of GSH.In addition.only calycosin and calycosin-7-O-glucoside were shown to inhibit XO activity in cell-free system,with an approximate IC_(50) value of 10μg/mL and 50μg/mL.Formononetin and calycosin had no significant influence on Bcl-2 or Bax protein contents.Conclusion Neuroprotection of formononetin,calycosin and calycosin-7-O-glucoside may be mediated by increasing endogenous antioxidants,rather by inhibiting XO activities or by scavenging free radicals. Objective To further investigate the neuroprotective effects of five isoflavonoids from Astragalus mongholicus on xanthine (XA)/xanthine oxidase(XO)-induced injury to PC12 cells.Methods PC12 cells were damaged bv XA/XO.The activities of antioxidant enzymes,MTT,LDH ,and GSH assays were used to evaluate the protection of these five isoflavonoids Contents of Bcl-2 family proteins were determined with flow cytometry.Results Among the five isoflavonoids including formononetin,ononin,9,10-dimethoxypterocarpan-3-O-β-D -glucoside, calycosin and calycosin-7-O-glucoside, calycosin and calycosin-7-O-glucoside were found to inhibit XA/XO-induced injury to PC12 cells. The EC(50) values ​​of formononetin and calycosin were 0.05μg/ mL.Moreovet,treatment with these three isoflavonoids prevented a decrease in the activities of antioxidant enzymes,superoxide dismutase(SOD)and glutathione peroxidase(GSH-Px),while formononetin and calycosin could prevent a significant deletion of GSH.In addition.only calycosi n and calycosin-7-O-glucoside were shown to inhibit XO activity in cell-free system, with an approximate IC_(50) value of 10μg/mL and 50μg/mL.Formononetin and calycosin had no significant influence on Bcl-2 or Bax protein contents.Conclusion Neuroprotection of formononetin, calycosin and calycosin-7-O-glucoside may be mediated by increasing endogenous antioxidants, the by by inhibiting XO activities or by scavenging free radicals.