Hi Hemlata

Several antidiabetic plants have  high level of polyphenols,such as; garlic (17.38mg/g) , onion (22.32 mg/g) and fenugreek (19.8 mg/g)!. Polyphenol has also improved insulin–dependent glucose uptake in muscle cells and adipocytes by translocation of glucose transporter, GLUT4, to plasma membrane mainly through induction of the AMP-activated protein kinase (AMPK) pathway.Polyphenols also inhibit α-glucosidase and α-amylase, the enzymes responsible for digestion of dietary carbohydrate to glucose.Plant-food polyphenols have been shown to attenuate hepatic gluconeogenesis via decreasing the activity of glucose-6-phosphatase and phosphoendolpyruvate carboxykinase (PEPCK) and down regulation of liver glucokinase expression .Several studies have shown that polyphenol compounds protect β-cells from oxidative-induced damages by enhancing the natural antioxidant system, inhibition of lipid peroxidation and stimulation on the β-cells .These suggest that the possible mechanisms for antidiabetic action of fenugreek may be due to stimulation of peripheral glucose uptake in tissues, modulation of carbohydrate metabolism and attenuation of intestinal absorption for dietary carbohydrate. Also it may act by increasing the insulin secretion from the existing pancreatic β cells.

therefore, anti-diabetic activity of fenugreek may be due to presence high level polyphenol compounds .

From the available data, it seems that the galactomannan-rich soluble fiber fraction of fenugreek would be responsible for the antidiabetic action of the seeds. In addition, insulinotrophic and antidiabetic properties have been related to the amino acid 4-hydroxyisoleucine that occurs in fenugreek at a concentration about 0.55%. In vitro studies have reported that this amino acid causes direct pancreatic β-cell stimulation. Inhibition of glucose transport also has been suggested as a possible mechanism. But, in my opinion, more consistent evidences are needed for a definitive response.

One has the remember the amount of fenugreek that will needed for daily consumption on the basis of contents of some of the known anti-diabetc compounds in it to elicit a measurable decrease in blood glucose levels. 

Fenugreek is bitter and not very appetizing. If one has to consume 50gm per day, I suspect that the bad taste will serve as a good motivator for not wanting to eat much and metabolic syndrome will get in better control (due to a precipitous drop in overeating)!  ;)