Journal of Ethnophannacology, 22 (1988) 45-49 Elsevier Scientific Publishers Ireland Ltd.

45

EFFECT OF TRIGolVE~I,A FOENUM GRACEUM ON BLOOD GLUCOSE LEVELS IN NORMAL AND ALLOXAN-DIABETIC MICE

MOHAMMAD AL1 AJABNOORa and ABDUL KARIM TILMISANYb

aDepartment of Clinical Biochemistry and bDepartment of Pharmacology, Faculty of Medicine & Allied Sciences, King Abdulaziz University, P.O. Box 9029, Jeddah-21413 (Saudi Arabiu/

(Accepted September 4,1987)

Summary

The hypoglycemic effects of a decoction and an ethanol extract of Trigeno& foenum graceum seeds on the serum glucose levels of normal and alloxan diabetic mice were studied. A single 0.5 ml oral dose of 40-80% decoctions to normal as well as alloxanized mice was followed by hypoglycemia developed over a 6-h period. Reduction in blood glucose concentration was highly significant, was maximum at 6 h and was dose- dependent. The hypoglycemia caused by the ethanol extract (200-400 mg/ kg) in alloxanized mice was also dose-dependent and 200 mg/kg was comparable in effect to 200 mg/kg tolbutamide.

Introduction

Trigoneh foenum graceum L. (Leguminosae) or “fenugreek” (in Arabic, Hulabaha) is a herbal medicine used in many parts of the world. Its leaves are used for their cooling properties and its seeds for their carminative, tonic and aphrodisiac effects Khopra et al., 1982). The curative gastric anti- ulcer action of the seed has been investigated in albino rats by Al-Meshal et al. (1985) in Saudi Arabia, and Sharma (1984) in India has documented the hypocholesterolemic effect on rats. Defatted seeds have been noted to prevent orally induced hyperglycemia and to decrease hyperglycemia and glycosuria in diabetic dogs (Ribes et al., 1986).

The present study investigates the hypoglycemic effects of a decoction and an ethanol extract of the seeds in normal and alloxan-treated diabetic male albino mice.

037%3741/88/$02.10 0 1988 Elsevier Scientific Publishers Ireland Ltd. Published and Printed in Ireland

46

Materials and methods

Preparation of extracts

A deco&ion was prepared by pouring 1 kg of whole fenugreek seeds, obtained from a local market and authenticated by the taxonomist at King Fahd Medical Research Centre (KFMRC), into 6 1 of boiling water and heating for 10 min. The liquid was cooled and filtered. This decoction (100%) was then diluted with normal saline to obtain 40%, 60% and 80% decoctions. After lyophilization, 10 ml of the 100% decoction was shown to contain 0.588 g of extractive.

An ethanol extract was prepared by extracting powdered fenugreek seeds in a soxhlet apparatus with 95% ethanol at 80°C for 24 h, after which the ethanol was evaporated by rotatory evaporator and all traces of ethanol eliminated by leaving the extract under vacuum overnight. The yield was 4.7% (w/w) in terms of the starting material.

Animals

Male albino mice, weighing 20-30 g, obtained from a random-bred colony of MFI strain mice, maintained on Formula No. 648 diet (Grain Silos and Flour Mills Organization, P.O. Box 5529, Jeddah, Saudi Arabia1 in the animal house of KFMRC, were divided into 11 groups of 5 animals each. Seven of these groups were rendered diabetic by injecting through the tail vein a single dose of 70 mg/kg alloxan monohydrate (BDH, U.K.1 in not more than 0.5 ml 0.9% saline (Lundquist and Rerup, 19671. The animals were tested for the development of hyperglycemia 48 h after alloxan administration. The animals of all the groups were fasted overnight (water allowed ad libituml prior to administration of either the decoction or the extract or the reference drug, tolbutamide.

Blood samples

All blood samples (50 ~11 for plasma glucose determination were collected in heparinized microhematocrit capillary tubes using the orbital sinus puncture technique described by Riley (19601 and then centrifuged for 2 min (microhematocrit centrifuge) within 60 min after obtaining the sample to prevent in vitro autoglycolysis by leukocytes (Goodenow and Malarkey, 19771.

Glucose de termination

Blood plasma glucose was estimated by the glucose oxidase method (Tietz, 19761 using a Beckman Glucose Analyzer 2 (Beckman Instrument, Inc., Fullerton, CA 929341.

47

Protocols

The overnight-fasted normal mice, after collecting a fasting blood sample, were orally administered 0.5 ml of one of the 40%, 60% or 80% decoctions. Control mice received 0.5 ml of 0.9% saline. Similarly, alloxanized mice were orally administered 0.5 ml of either the 40%, 60% or 80% decoctions, 200 or 400 mg/kg of the ethanol extract in 0.5 ml saline, 200 mg/kg tolbutamide in 0.5 ml saline (Ajabnoor et al., 19841 or drug-free 0.5 ml saline (diabetic control). Blood samples were collected 2,4,6,8 and 24 h after administration.

Results and discussions

The blood glucose of mice treated with a single oral dose of either deco&ion or ethanol extract decreased significantly as compared to the corresponding controls (Tables 1,21 and reached its maximum 6 h P < 0.00051 after administration. The maximum decreases in blood glucose of normal mice after administration of 40%, 60% or 80% decoction were 25%, 26% and 33%, respectively (Table 11, and in alloxanized mice were 26%, 29% and 38%, respectively (Table 21. It was observed that the greater the concentration of the extract administered, the larger was the decrease in glucose level. Moreover, the effect was accentuated when the initial glucose level was high (Table 21. Similar effects were obtained with 200 mg/kg and 400 mg/kg of the ethanol extract (Table 21 where the decreases in blood glucose were 31% and 43%, respectively. The effect of 200 mg/kg tolbutamide was a 29% decrease in blood glucose (Table 21 with the maximum effect apparent at 4 h.

The findings of the present investigation clearly indicate that the seeds of T. foenum graceum possess potential antidiabetic activity. This confirms the earlier findings of Ribes et al. (19681 in dogs. Since extracts were used instead of the whole seed and since the experiment was conducted on fasting mice, the effect could not be due to the gastrointestinal action of fibre. Tolbutamide significantly decreased P < 0.00051 the blood glucose level in alloxanized mice (Table 21 which indicated only partial destruction of the beta-cells by alloxan as tolbutamide is not effective in the total absence of secretory cells (Lebovitz and Feinglos, 19781. This suggests that the mechanism of antidiabetic action of the seeds may be similar to that of tolbutamide although other mechanisms are possible.

The chemical nature of the active compound(s) responsible for hypoglycemia is unknown. However, phytochemical screening has revealed the presence of alkaloids, sterols (Shani et al., 19741, saponin monohydroxysapogenins (Ehjoba and Hardman, 19851 and diosgenin (Anis and Aminuddin, 19851 in fenugreek seeds. Moreover, a hypoglycemic betain (trigonelline) has been isolated from T. foenum graceum (Nadkarni, 1954; Bever, 1980). However, Shani et al. (19741 concluded that coumarin and nicotinic acid were the main hypoglycaemic constituents in fenugreek seeds.

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49

One or more of these compounds may be responsible for the antidiabetic activity of fenugreek seed; therefore, more work is needed to determine the exact nature of the active principle(s) and the mechanism(s) of action.

References

Ajabnoor, M.A., Al-Yahya, M.A., Tariq, M. and Jayyab, A.A. (19841 Antidiabetic activity of Teucrium oliveriunum. Fitoterapiu 55, 227-230.

Al-Meshal, I.A., Parmar, N.S., Tariq, M. and Aqeel, A.M. (19851 Gastric anti-ulcer activity in rats of Trigonella foenum graceum (Hu-Lu-Pal. Fitoterapia 56, 232-235.

Anis, M. and Aminuddin (1985) Estimation of diosgenin in seeds of induced autoploid Trigonella foenum graceum. Fitoterapia 56, 51- 52.

Bever, B.O. (19801 Oral hypoglycaemic plants in West Africa. Journal of Ethnopharmacology 2, 119- 127.

Chopra, R.N., Chopra, I.C., Honda, K.L. and Kapur, L.D. (19821 Choprab Indigenous Drugs of

India, Academic Publishers, Calcutta, New Delhi, India, pp. 582. Ehjoba, A.A. and Hardman, R. (1985) Fermentation of powdered fenugreek seeds for increased

sapogenin yields. Fitoterapiu 56, 368-370.

Goodenow, T. and Malarkey, W. (1977) Leukocytosis and artifactual hypoglycemia. Journal of the America1 Medical Association 237, 1961- 1962.

Lebovitz, H.E. and Feinglos, M.N. (19781 Sulfonylurea drugs: mechanism of action and therapeutic usefulness. Diabetes Care 1, 189.

Lundquist, I. and Rerup, C. (19671 On the development of alloxan diabetes in mice. European

Journal of Pharmacology 2,35-41.

Nadkarni, K.M. (1954) Indian Materiu Medica, Popular Book Depot, Bombay, India, pp. 1240- 1243.

Ribes, G., Sauvarire, Y., Jean, C., Valette, G., Chendon, D., Trible, E.R., Loubatieres, M. and Madelience, M. (19841 Effect of fenugreek seeds on endocrine pancreatic secretion in dogs. Annals of Nutrition and Metabolism 28,37 - 43.

Riley, V. (1960) Adaptation of orbital sinus bleeding technique to rapid serial blood studies. Proceedings of the Society for Experimental Biology and Medicine 104, 751-754.

Shani, J., Goldschmied, A., Joseph, B., Ahronson, Z. and Sulman, F.G. (19741 Hypoglycaemic effect of Trigonella foenum graceum and Lurpinus termink (Leguminosael seeds and their major alkaloids in alloxan diabetic and normal rats. Archives internationales de

Pharmacodynamie et de Therapie 210,27.

Sharma, R.D. (19841 Hypocholesteronic activity of fenugreek. Nutrition Reports International 30, 221-231.

Tietz, N.W. (1976) Carbohydrates In: Fundamentals of Clinical Chemistry, W.B. Saunders Company, Philadelphia, London, Toronto, pp. 245-247.