The methanolic extracts from branches (BEP) and leaves (LEP) of Eysenhardtia platycarpa significantly decreased the blood glucose levels in normal and streptozotocin (STZ)-induced diabetic rats. One new flavone, (1"R)-5,4',1"-trihydroxy-6,7-(3",3"-dimethylchroman)flavone (1), together with the known compounds 5,7-dihydroxy-6-methyl-8-prenylflavanone (3), 5,7-dihydroxy-8-methyl-6-prenylflavanone (4), 5,7-dihydroxy-6-prenylflavanone (5), 5,7-dihydroxy-8-prenylflavanone (6), 3-O-acetyloleanolic acid (7), oleanolic acid, 3beta-acetoxy-11alpha,12alpha-epoxy-oleanan-28,13beta-olide, lupeol, betulinic acid, beta-sitosterol, beta-sitosteryl beta-D-glucopyranoside, beta-sitosteryl palmitate, and 3-O-methyl-myo-inositol were isolated from BEP. Additionally, one new flavanone, (2S)-4'-O-methyl-6-methyl-8-prenylnaringenin (2), as well as the known compounds 3, 4, 6, 4'-O-methyl-8-prenylnaringenin (8), and 5-hydroxy-7-methoxy-8-prenylflavanone (9) were isolated from LEP. 3-O-Acetyloleanolic acid (7), identified as the major constituent of BEP, showed a significant decrease (31 mg/kg of body weight, P < 0.05) in the glucose level of STZ-induced diabetic rats. The obtained results correlate with the traditional use of this species.

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Recently, attention has been focused on the relationship between reactive oxygen species (ROS) and several disorders including aging, various inflammatory diseases, carcinogenesis, neurodegenerative diseases, and diabetes. 1) In fact, diabetes is usually accompanied by increased production of ROS 2) and impaired antioxidant defense, 3) indicating a central contribution of ROS to the onset, progression, and pathological consequences of diabetes. There is considerable evidence that chronic hyperglycemia is the proximate cause of retinopathy, kidney failure, neuropathies, and macrovascular diseases in diabetes.1) In addition, it has been demonstrated that b cells are particularly susceptible to oxidative damage. 4)Therefore, as hyperglycemia worsens, b cells steadily deteriorate, secrete less insulin, and participate in a downward spiral of loss of pancreatic functions.The current treatments of diabetes are based on a combination of diet, oral hypoglycemic agents, and insulin intake, which focus on decreasing the blood glucose level.5) Although some oral hypoglycemic agents have been associated with enhancement of the antioxidant system, 6) they do not prevent the gradual loss of b-cell functions, which is known to account for gradual deterioration of glucose homeostasis. Therefore, the treatment of micro-and macrovascular complications has required the combined use with several herbal preparations and dietary supplements.7) Many natural products 8,9) and medicinal plants 7) have been shown to significantly reduce oxidative stress and increase the antioxidant endogenous system, which represent a important property of plant medicines used for the treatment of several diseases including diabetes. In this sense, approximately 306 species from 235 genera and 93 families have been used empirically as hypoglycemic agents in Mexican traditional medicine. 10)Eysenhardtia platycarpa, E. subcoriacea, and E. punctata, known indiscriminately as 'palo dulce' (sweet wood), are traditionally used for the treatment of bladder infections and kidney diseases related to diabetes. 11) Eysenhardtia is a small genus that comprises 14 species indigenous to North and Central Mexico.12) Previous studies on Eysenhardtia species have highlighted the hypoglycemic activity of E. polystachya 13) and the antihyperglycemic activity of E. platycarpa, 14) as well as the isolation of cytotoxic flavonoids 15,16) and 3-O-acetyloleanolic acid [which displayed antihyperglycemic activity in streptozotocin (STZ)-induced diabetic rats 14) ]. As part of our screening of plants for the isolation of substances with antioxidant and antihyperglycemic potential, 14,17) this study was conducted to A) assess the antioxidant effects of extracts from E. platycarpa, E. punctata, and E. subcoriacea, as well as of compounds 1-8, natural constituents isolated from E. platycarpa (Chart 1), in a rat pancreas model and in a 1,1 diphenyl-2-picrylhydrazyl (DPPH) radical scavenger assay; B) synthesize 1, which displayed a protective effect against 2,2-azo-bis(2-amidinopropane...

Subcoriacin (1) is a 3-aryl-6-prenylcoumarin isolated from Eysenhardtia subcoriacea that has shown antioxidant activity in vitro, and has shown to scavenge free radicals and also to improve the reduced glutathione levels in pancreatic homogenates. The present investigation evaluates the protective effect of 1 against oxidative injury in normal and streptozotocin (STZ)-induced diabetic rats. The i.p. administration of 1 at a dose of 100 mg/kg body weight for 5 d, significantly decreased blood glucose levels and improved the endogenous antioxidant system. Also, a significant increase in the activities of the antioxidant enzymes glutathione peroxidase (GSHPx), superoxide dismutase (SOD) and catalase (CAT) occurred. Combined treatment of rats with 1 (100 mg/kg) and STZ significantly reduced the pancreatic levels of thiobarbituric acid reactive substances (TBARS) levels. Likewise, significant increases in the activities of the antioxidant enzymes together with a decrease in blood glucose levels in both treatments were observed. The results demonstrate and support the relationship between the hypoglycemic and antioxidant activities displayed by the natural compound 1.