Objective: To study the protective effects of Cassia obtusifolia extract（COE） on oxidative stress of lens in streptozotocin（STZ）-induced diabetic mice.Method: STZ（130 mg·kg-1） was intravenously injected from the tail vein to induce diabetes in mice

which were randomly divided into STZ model

metformin positive control（300 mg·kg-1）

and different dosages of COE（50

150

450 mg·kg-1）

with 10 mice in each group.Metformin and COE were given to mice once daily for 10 consecutive days by oral administration

while normal control and STZ model groups were given water only.Blood glucose level and parameters of oxidative stress oxygen radical absorbance capacity（ORAC）

malonaldehyde（MDA）

nitric oxide（NO）

L-glutathione（GSH）

total superoxide dismutase（T-SOD） and glutathione eroxidase（GSH-Px） were detected in mice lens.Result: STZ injection increased plasma glucose significantly and also induced oxidative stress in mice lens.Although COE was not effective on the elevated blood glucose level

it could significantly lower the contents of NO and MDA in lens（P<0.01）.At the same time

ORAC and GSH levels of lens were significantly increased（P<0.01）.The activity of T-SOD and GSH-Px was also increased（P<0.01）.Conclusion: COE could improve oxidative stress conditions in lens of STZ-induced diabetic mice.The mechanism should be related to the elimination of free radicals and inhibition of lipid peroxidation.