Trigonella foenum-graecum (fenugreek) seeds have been documented as a traditional plant treatment for diabetes. In the present study, the antidiabetic properties of a soluble dietary fibre (SDF) fraction of T. foenum-graecum were evaluated. Administration of SDF fraction (0·5 g/kg body weight) to normal, type 1 or type 2 diabetic rats significantly improved oral glucose tolerance. Total remaining unabsorbed sucrose in the gastrointestinal tract of non-diabetic and type 2 diabetic rats, following oral sucrose loading (2·5 g/kg body weight) was significantly increased by T. foenum-graecum (0·5 g/kg body weight). The SDF fraction suppressed the elevation of blood glucose after oral sucrose ingestion in both non-diabetic and type 2 diabetic rats. Intestinal disaccharidase activity and glucose absorption were decreased and gastrointestinal motility increased by the SDF fraction. Daily oral administration of SDF to type 2 diabetic rats for 28 d decreased serum glucose, increased liver glycogen content and enhanced total antioxidant status. Serum insulin and insulin secretion were not affected by the SDF fraction. Glucose transport in 3T3-L1 adipocytes and insulin action were increased by T. foenum-graecum. The present findings indicate that the SDF fraction of T. foenum-graecum seeds exerts antidiabetic effects mediated through inhibition of carbohydrate digestion and absorption, and enhancement of peripheral insulin action.

Extracts of Momordica charantia fruit pulp, seed, and whole plant were tested for their hypoglycemic effects on normal and diabetic rat models. The results show that during the oral glucose tolerance test the peak blood glucose values in rats are obtained much earlier (15-45 min) than in human subjects (around 60 min). Pulp juice of M. charantia lowered fasting blood glucose levels in normal rats (p < 0.05 at 120 min); the effect was more pronounced with the saponin-free methanol extract of the pulp juice (p < 0.05 at 60 min and p < 0.01 at 120 min). The pulp juice also had a significant hypoglycemic effect in the glucose-fed normal rats when the extract was fed 45 minutes before the oral glucose load [percentage increments over basal value (M +/- SE): 85 +/- 10 in the control group vs. 54 +/- 7 in the pulp juice group, p < 0.01]. In the IDDM model rats the pulp juice had no significant effect on blood glucose levels either in fasting or postprandial states. In the NIDDM model rats the saponin-free methanol extract of juice produced a significant hypoglycemic effect both in fasting (p < 0.05 at 120 min) and in postprandial states (sum of percentage increments over basal value: 140 +/- 26 in the control vs. 71 +/- 7 in the pulp juice group, p < 0.05). Methanol extracts of seed and of whole plant, and saponin-free methanol extract of whole plant produced no hypoglycemic effects in normal or IDDM model rats either in fasting or in postprandial states.(ABSTRACT TRUNCATED AT 250 WORDS)

Ocimum sanctum leaves have previously been reported to reduce blood glucose when administered to rats and humans with diabetes. In the present study, the effects of ethanol extract and five partition fractions of O. sanctum leaves were studied on insulin secretion together with an evaluation of their mechanisms of action. The ethanol extract and each of the aqueous, butanol and ethylacetate fractions stimulated insulin secretion from perfused rat pancreas, isolated rat islets and a clonal rat -cell line in a concentration-dependent manner. The stimulatory effects of ethanol extract and each of these partition fractions were potentiated by glucose, isobutylmethylxanthine, tolbutamide and a depolarizing concentration of KCl.Inhibition of the secretory effect was observed with diazoxide, verapamil and Ca 2+ removal. In contrast, the stimulatory effects of the chloroform and hexane partition fractions were associated with decreased cell viability and were unaltered by diazoxide and verapamil. The ethanol extract and the five fractions increased intracellular Ca 2+ in clonal BRIN-BD11 cells, being partly attenuated by the addition of verapamil. These findings indicated that constituents of O. sanctum leaf extracts have stimulatory effects on physiological pathways of insulin secretion which may underlie its reported antidiabetic action.

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