Alpha-Glucosidase activity of Smallanthus Sonchifolius (Yacon) roots

HABIB N.; HONORÉ S.M.; GENTA S.B.; SANCHEZ S.S.

Córdoba

Congreso; I Reunion Internacional de Ciencias Farmaceuticas; 2010

RICiFa

Introduction: Alpha-glucosidase in the small intestine plays a physiologically important role for the digestion process of dietary carbohydrate. The inhibitors of this enzyme, in consequence, are known to reduce the postprandial hyperglycemia and may contribute to the optimal glycemic control in the management of obesity and diabetes. Smallanthus sonchifolius [Poepp. &Endl.] H.Robinson or yacon is a native specie of South America belonging to the Asteraceae family. In recent work we have demonstrated that the administration of syrup obtained from yacon roots produced beneficial health effects on obese women with insulin resistance (1). In the present study we have investigated the effect of yacon root flour to control the postprandial hyperglycemia and also determinated its possible mechanism of action through studies in Wistar rats and in vitro alpha-glucosidase inhibition assay. Materials and Methods: Tolerance Glucose and Sucrose Tests: adult male Wistar rats weighting 200-220g were selected for all experiments. The animals were divided as follow: a) treated daily with yacon roots (0,95g dw/Kg bw and 10,5g dw/Kg bw), before eating, during a 30 days period, b) animals without treatment. Oral Tolerance Glucose and Sucrose were carried out in all animal groups.  In vitro Inhibition assay for the alpha-glucosidase activity: experiment was carried out by the method described by Li et al., 2004 (2). Acarbose was used as positive control. Released glucose was quantified with a commercial glucose oxidase-based assay (SigmaR) and was read at 540nm. Inhibitory activity was reported as mg of free glucose.  Maceration, decoction, infusion and syrup (4, 16, 64ug/ml) was obtained from yacon roots and used for inhibitory alpha-glucosidase assay. Statistical analysis: The statistical significance was assayed using analysis of variance (ANOVA). A p value ¡Ü0,05 was considered statistically significant. Results: Oral Glucose Tolerance Test: The oral administration of yacon roots caused a rapid decreased in the hyperglycemic peak after glucose loading in both animal groups (with and without treatment). Oral Sucrose Tolerance Test: Animals underwent sucrose tolerance curves 15 min after water, acarbose or yacon roots. After 30 min, yacon roots decreased the glycemic peak, compared with the control. This effect was dose-dependent being 10,5g dw/Kg bw the most effective dose. The rats treated with yacon roots during 30 days showed a better response to oral sucrose. Inhibition of alpha-glucosidase activity: Maceration, decoction, infusion and syrup obtained from yacon roots inhibited alpha-glucosidase activity. This inhibition was significant in relation with negative control and was even lower than with acarbose, a therapeutic drug used as positive control. Discussion: Our results indicate that the control of post-prandial glucose level showed by yacon roots might involve an anti-hyperglycemic effect, mediated by the inhibition of carbohydrate digestion. This could be possible by retarding the postprandial glucose level by inhibition of intestinal alpha-glucosidase as shown by Shim et al. (3). References (1) Genta SB, Cabrera W, Habib NC, Pons J, et al. Clinical Nutrition 28:182-187 (2009). (2)Li Y, Peng G et al. Life Science 75, 1735-46 (2004). (3) Shim YJ, Doo HK, Ahn SY, Kim YS, et al. J Ethnopharmacol 85:283-287 (2003).