title: The hypoglycemic activity of Lithocarpus polystachyus Rehd. leaves in the experimental hyperglycemic rats.
abstract: BACKGROUND
  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.
  
  
  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<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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: School of Chinese Pharmaceutical Science, Guangzhou University of Chinese Medicine, University Town, Guangzhou 510006, China.
authors.forename: Shao-Zhen
authors.initials: SZ
authors.lastname: Hou
authors.forename: Shu-Xian
authors.initials: SX
authors.lastname: Chen
authors.forename: Song
authors.initials: S
authors.lastname: Huang
authors.forename: Dong-Xu
authors.initials: DX
authors.lastname: Jiang
authors.forename: Cai-Jie
authors.initials: CJ
authors.lastname: Zhou
authors.forename: Chang-Qing
authors.initials: CQ
authors.lastname: Chen
authors.forename: Ying-Min
authors.initials: YM
authors.lastname: Liang
authors.forename: Xiao-Ping
authors.initials: XP
authors.lastname: Lai
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001798:Blood Proteins / Q000378:metabolism; D002097:C-Reactive Protein / Q000378:metabolism; D002784:Cholesterol / Q000097:blood; D003404:Creatinine / Q000097:blood; D003921:Diabetes Mellitus, Experimental / Q000097:blood / Q000188:drug therapy* / Q000473:pathology; D029962:Fagaceae / Q000737:chemistry*; D005419:Flavonoids / Q000494:pharmacology / Q000627:therapeutic use*; D006023:Glycoproteins / Q000378:metabolism; D006943:Hyperglycemia / Q000097:blood / Q000188:drug therapy / Q000473:pathology; D007004:Hypoglycemic Agents / Q000494:pharmacology / Q000627:therapeutic use*; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D008099:Liver / Q000187:drug effects / Q000473:pathology; D008297:Male; D008315:Malondialdehyde / Q000097:blood; D009584:Nitrogen / Q000097:blood; D008517:Phytotherapy; D010936:Plant Extracts / Q000494:pharmacology / Q000627:therapeutic use; D018515:Plant Leaves; D051381:Rats; D017207:Rats, Sprague-Dawley; D013482:Superoxide Dismutase / Q000097:blood; D014280:Triglycerides / Q000097:blood; D014508:Urea / Q000097:blood; D000093422:Glycated Serum Proteins
chemical_list: D001786:Blood Glucose; D001798:Blood Proteins; D005419:Flavonoids; D006023:Glycoproteins; D007004:Hypoglycemic Agents; D007328:Insulin; D010936:Plant Extracts; D014280:Triglycerides; D008315:Malondialdehyde; D014508:Urea; D002097:C-Reactive Protein; D002784:Cholesterol; D003404:Creatinine; D013482:Superoxide Dismutase; D009584:Nitrogen; D000093422:Glycated Serum Proteins