ฤทธิ์และกลไกการออกฤทธิ์ของสารสกัดแห้ม ต่อระดับน้ำตาล ในเลือด ของหนูปกติและหนูเบาหวาน / วัลยา จิตตประสาทศีล = Effects and mechanism of action of Coscinium fenestratum extract on blood glucose level in normal and diabetic rats / Wanlaya Jittaprasatsin
Coscinium fenestratum (Gaertn.) Colebr. or "Hamm" has been widely used as a traditional medicine. The request to use this plant in diabetes is increasing. However, the scientific information in biological activities of C. fenestratum is limited, therefore, the study on pharmacological effects of this plant has been necessary. The objective of this study was to investigate 1) the effects of C. fenestratum extract (CFE) on blood glucose level in normal and diabetic rats 2) the stimulatory effects on insulin secretion from perfused rat pancreas and 3) the inhibitory effects of rat intestinal alpha-glucosidase, maltase and sucrase. The anti-hyperglycemic effects of CFE on plasma glucose levels were studied in both normal and streptozotocin-induced diabetic rats by performing OGTT with several kinds of sugar, glucose, maltose and sucrose. In normal rats, the CFE at concentrations of 250-1000 mg/kg inhibited increases of plasma glucose levels in all three kinds of sugar-loaded rats in a dose-dependent manner. In diabetic rats, CFE (500 mg/kg) significantly decreased plasma glucose levels in glucose and maltose loaded rats, while it did not demonstrated the statistical hypoglycemic effect in sucrose-loaded rats. We further investigated the stimulatory effect of CFE on insulin secretion from perfused rat pancrease and its inhibitory activity on rat intestinal alpha-glucosidase, maltase and sucrase. The result showed that CFE (10 microgram/ml) significantly increased insulin secretion in a biphasic pattern, a peak follow by sustained phase and berberine at the same concentration slightly and gradually stimulated insulin secretion in a monophasic pattern, indicating that the in vivo hypoglycemic effect of CFE was due to stimulation of insulin secretion from pancreatic beta-cells. In addition, CFE inhibited in vitro activities of maltase better than sucrase, which was similar to acarbose. Taken together, it is concluded that the crude ethanol extract of C. fenestratum had anti-hyperglycemic action in both normal and STZ-induced diabetic rats. The mechanisms underlying hypoglycemic activity of CFE were at least partly due to stimulation of insulin secretion and inhibition of intestinal alpha-glucosidase, maltase and sucrase. Thus, this compound is worth to be developed as a new drug for treating diabetes in the future.