School of Chinese Pharmaceutical Science, Guangzhou University of Chinese Medicine, University Town, Guangzhou 510006, China.
J Ethnopharmacol. 2011 Oct 31;138(1):142-9. doi: 10.1016/j.jep.2011.08.067. Epub 2011 Sep 8.
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.
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.
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<0.01 or p<0.05). ST-3 administration for four weeks also significantly reduced the fasting serum insulin and C-peptide level and improved the insulin tolerance (p<0.05). In type 1 diabetic rats, ST-3 supplement for three weeks caused significant reduction in fasting blood glucose, total cholesterol, triglyceride, urea nitrogen, creatinine and liver mass, along with significantly inhibiting the decline of insulin level compared to diabetic control (p<0.05 or p<0.01).
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.
石栎的叶子在华南民间医学中被用于治疗糖尿病、高血压和癫痫等疾病。本研究旨在探讨石栎叶子的潜在抗糖尿病作用。
2 型糖尿病大鼠连续口服石栎叶子的三种不同提取物 4 周（水提物[ST-1]、醇提物[ST-2]、富含黄酮类化合物的馏分[ST-3]）。实验结束时，检测生化参数，并切除肝脏和胰腺进行组织学研究。比较三种提取物的药理试验结果后，选择生物活性最好的提取物进一步研究其对 2 型和 1 型糖尿病大鼠的抗糖尿病作用。
与 ST-1 和 ST-2 相比，ST-3 对 2 型糖尿病大鼠血糖、糖化血清蛋白、胆固醇、甘油三酯、丙二醛、超氧化物歧化酶的调节以及肝损伤的减轻作用更好（p<0.01 或 p<0.05）。ST-3 连续给药 4 周还显著降低了空腹血清胰岛素和 C 肽水平，改善了胰岛素耐量（p<0.05）。在 1 型糖尿病大鼠中，ST-3 补充 3 周可显著降低空腹血糖、总胆固醇、甘油三酯、尿素氮、肌酐和肝质量，同时显著抑制与糖尿病对照组相比胰岛素水平的下降（p<0.05 或 p<0.01）。
石栎叶富含黄酮类化合物的馏分（ST-3）在实验性糖尿病大鼠中的有益作用优于乙醇或水提取物，这意味着草药叶的生物活性可能归因于黄酮类化合物的存在。结果还强烈表明，ST-3 的抗糖尿病作用可能是通过多种作用机制，包括血脂和抗氧化调节来实现的。结果表明，石栎富含黄酮类化合物的水馏分在 2 型和 1 型糖尿病中具有显著的保护活性。
