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The transformation of fenugreek subfractions, rich in steroid saponins, was studied upon their passage through the digestive tract to determine the contribution of saponins and/or diosgenin and other steroid sapogenins to the hypocholesterolemic effect of fenugreek seeds. Feces of alloxan diabetic dogs fed fenugreek subfractions were analyzed, and diosgenin, smilagenin and gitogenin were identified and measured using capillary gas chromatography/mass spectrometry. Our results show that saponins are, in part (about 57%), hydrolyzed into sapogenins in the digestive tract. It appears that saponins may be implicated, alone or together with diosgenin, in the observed hypocholesterolemic effect of fenugreek seeds in diabetic dogs.

The components of fenugreek seeds were separated and analyzed to determine which fraction of the seed had hypoglycemic activity. These fractions were administered orally to normal or diabetic dogs for 8 days. The effect on blood glucose and pancreatic hormones was studied in normal dogs. The lipid extract had no effect; the defatted fraction (50.2% fibers: gum 17.7%, hemicellulose 22%, cellulose 8.3%, lignin 2.2%) lowered basal blood glucose level, plasma glucagon and somatostatin levels and reduced the orally induced hyperglycemia. The addition of this fraction to the insulin treatment resulted in a decrease of hyperglycemia and glycosuria in diabetic dogs. The results indicate that the defatted part is responsible for the antidiabetic action. However, the present study does not permit one to know whether the effects are caused by an unknown pharmacological compound or by the gastrointestinal action of fibers.

We have previously shown that the antidiabetic property of fenugreek seeds (Trigonella foenum graecum L.) is associated with the defatted seed material which is rich in fibers, saponins, and proteins. In the present work this defatted preparation was divided into two subfractions: subfraction "a" which contains the testa and endosperm and is rich in fibers (79.6%); and subfraction "b" which contains the cotyledons and axes and is rich in saponins (7.2%) and proteins (52.8%). We investigated the effects of each subfraction on hyperglycemia and the levels of pancreatic hormones when chronically administered to alloxan-diabetic dogs. Each subfraction was studied separately and was given to the dogs per os (mixed with the two daily meals), in addition to the insulin treatment (which was kept the same throughout the experiment) for a period of 21 days. The addition of subfraction "a" to insulin treatment resulted in a clear decrease of hyperglycemia and glycosuria accompanied by a reduction of the high plasma glucagon and somatostatin levels in diabetic dogs. The treatment also decreased the hyperglycemic response to the oral glucose tolerance test. In contrast the chronic administration of subfraction "b" had no effect on hyperglycemia or on the levels of pancreatic hormones in diabetic dogs. Our results show that the antidiabetic properties of fenugreek seeds are contained in the testa and endosperm. Although this subfraction is rich in fibers (high viscosity; 115 cP), it is not possible to exclude the existence of one or more unknown active pharmacological compounds in this subfraction of the seed.