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Iridal, a triterpenoidic compound extracted from Iris germanica L., was previously shown to have an interesting activity on two cultured human tumor cell lines (A2780 and K562). In the present work, this same product was tested in vitro on Plasmodium falciparum chloroquine-resistant and -sensitive strains, in vivo on P. vinckei, and on some Candida albicans and C. parapsilosis strains too. The IC(50) obtained in vitro on human malaria strain ranged from 1.8 to 26.0 microg/ml and the ED(50) in vivo is about 85 mg/kg/day by intraperitoneal route. The minimal inhibitory concentrations were higher than to 50 microg/ml, whatever the strain of yeast tested. This product presents an antiplasmodial activity similar to that obtained with extracts from the plant Azadirachta indica classically taken as reference in malaria phytomedicine. Conversely iridal shows no important antifungal activity. The specific activity of iridal on human malaria parasite and on tumor cell lines is discussed.

Spirostanol saponin permeabilization of Candida albicans cells resulted in phosphate (Pi) leakage from these cells. Pre-incubation of C. albicans suspension cultures with ergosterol or cycloiridals inhibited Pi leakage when cells were subjected to saponins. Saponins were shown to precipitate ergosterol but not cycloiridals. Inhibition of Pi leakage in the presence of cycloiridals could thus be due to their incorporation into cell membranes. Cycloiridals, which were previously shown to modify fluidity parameters in artificial phospholipid bilayers, seem in vivo to have a protective effect on membranes against surfactant (saponin) injury.

A study was made of the enzyme in fenugreek implicated in the biosynthesis of 4-hydroxyisoleucine, which is an unusual amino acid known for its insulin stimulating effect. 4-Hydroxyisoleucine was detected by HPLC following isoleucine incubation with a cell-free extract from etiolated 6-day-old fenugreek seedlings in the presence of various cofactors. The reaction showed that 4-hydroxyisoleucine formation is dependent on the presence of Fe2+, 2-oxoglutarate, ascorbate and oxygen. This suggests that a 2-oxoacid dependent dioxygenase plays a key role in this biosynthetic pathway.

The seeds of fenugreek (Trigonella foenum graecum L.) are traditionally assumed to have restorative properties. We have recently shown that a fenugreek seed extract containing steroid saponins increased food consumption and induced hypocholesterolemia in rats. This study aims to investigate the specific role of purified steroid saponins in these properties. For this purpose, an original technique for extraction and purification of steroid saponins was carried out. Thereafter, the effects of these steroid saponins were investigated on feeding behavior and metabolic endocrine changes in normal and diabetic rats. All the steroid saponins (furostanol type) were extracted from the seeds and separated from all other constituents of the entire extract by using several purification procedures to give an extract containing at least 90% of steroid saponins. Pharmcological experiments were performed in vivo in normal and streptozotocin diabetic rats: steroid saponins were administered chronically mixed with food (12.5 mg/day per 300 g body weight). Our data show that the treatment with steroid saponins significantly increased food intake and the motivation to eat in normal rats, while modifying the circadian rhythm of feeding behavior; it also stabilized the food consumption in diabetic rats, which resulted in a progressive weight gain in these animals, in contrast to untreated diabetic controls. Both in normal and diabetic rats, steroid saponins decreased total plasma cholesterol without any change in triglycerides. In conclusion, the present work reports a clear methodology to obtain all the steroid saponins and demonstrates that these saponins enhance food consumption and motivation to eat, and reduce plasma cholesterol levels in rats.

Fenugreek seeds (Trigonella foenum graecum L.) are assumed to have restorative and nutritive properties. The present work was designed to investigate the effects of a fenugreek seed extract on feeding behaviour. Experiments were performed to determine food consumption and motivation to eat as well as metabolic-endocrine changes in chronically treated animals. Male Wistar rats were given the seed extract orally (10 and 100 mg/day per 300 g body weight), mixed together with food, and control animals were monitored in parallel. The results show that chronic oral administration of the fenugreek extract significantly increases food intake and the motivation to eat. The treatment, however, does not prevent the anorexia nor the decreased motivation to eat induced by d-fenfluramine (2 mg/kg, IP). An increase in plasma insulin and a decrease in total cholesterol and very low-density lipoprotein (VLDL)-low-density lipoprotein (LDL) total cholesterol were also observed. In conclusion, chronic administration of a fenugreek seed extract enhances food consumption and motivation to eat in rats and also induces hyperinsulinemia as well as hypocholesterolemia.

Fractions of fenugreek seed were added to the diet of normal or diabetic hypercholesterolaemic dogs for 8 days. The effects on levels of blood glucose, plasma glucagon and plasma cholesterol were investigated. The lipid extract had no effect. The defatted fraction which is rich in fibres (53.9%) and contains 4.8% of steroid saponins significantly lowered basal blood glucose (P less than 0.02), plasma glucagon (P less than 0.01) and plasma cholesterol (P less than 0.02) levels in normal dogs. The addition of this fraction to the food of diabetic hypercholesterolaemic dogs caused a decrease of cholesterolaemia (P less than 0.02) and reduced hyperglycaemia. In conclusion, the defatted portion of fenugreek seed induces a hypocholesterolaemic effect.