The hypoglycemic activity of Lithocarpus polystachyus Rehd. leaves in the experimental hyperglycemic rats

Abstract Ethnopharmacological relevance Leaves of Lithocarpus polystachyus Rehd. are used for the treatment of disorders such as diabetes, hypertension, and epilepsy in folk medicine of South China. The possible antidiabetic effects of the leaves were investigated in experimental type 2 and type 1 diabetic rats. Materials and methods Type 2 diabetic rats received orally three different extracts of Lithocarpus polystachyus Rehd. leaves for 4 weeks (aqueous extract [ST-1], ethanol extract [ST-2], flavonoid-rich fraction [ST-3]). At the end of the experiment biochemical parameters were tested and livers and pancreases were excised for histological study. After the comparison of the pharmacological test results of the three extracts, the one which showed the best bioactivity was further studied to confirm its antidiabetes effect on both type 2 and type 1 diabetic rats. Results Compared to ST-1 and ST-2, ST-3 had better effects on regulation of blood glucose, glycosylated serum protein, cholesterol, triglyceride, malondialdehyde, superoxide dismutase and attenuation of liver injury in type 2 diabetic rats ( p p p p p Conclusion The flavonoid-rich fraction of Lithocarpus polystachyus Rehd. leaves (ST-3) had better beneficial effect than that of the ethanol or aqueous extract in experimental diabetic rats, which means that the bioactivity of the herbal leaves is probably due to the presence of flavonoids. The results also strongly suggest that the antidiabetic effect of ST-3 was possibly through multiple mechanisms of action including blood lipid and antioxidant mediation. The results indicated that the aqueous flavonoid-rich fraction of Lithocarpus polystachyus Rehd. leaves possessed significant protective activity in type 2 and type 1 diabetes.