Gen. Pharmac. Vol. 21, No. 5, pp. 779-782, 1990 Printed in Great Britain. All rights reserved

0306-3623/90 $3.00 + 0.00 Copyright © 1990 Pergamon Press plc

HYPOGLYCAEMIC ACTIVITY OF SOME MEDICINAL PLANTS IN SRI-LANKA M. R. FERNANDO, M. I. THABREW* and E. H. KARUNANAYAKE 1 Department of Biochemistry, Faculty of Medicine, University of Ruhuna and )Department of Biochemistry, Faculty of Medicine, University of Colombo, Sri-Lanka

(Received 4 December 1989) Abstract--I. Investigations were carried out to determine whether aqueous extracts ofOsbeckia octandra, Artocarpus heterophyllus and Bambusa oulgaris truly possess oral hypoglycaemic activity. 2. All three plant extracts significantly lowered the fasting blood glucose level and markedly improved glucose tolerance in Sprague-Dawley rats. 3. A maximum hypoglycaemic activity was observed at +3 hr with O. octandra and B. vulgaris; with A. heterophyllus a maximum effect was not observed even at + 5 hr. 4. The hypoglycaemic activity of O. octandra was comparable with that of tolbutamide while that of A. heterophyllus or B. vulgaris was better than that of tolbutamide. 5. The magnitude of the hypoglycaemic effects varied with the dosage used and the time of storage (except with A. heterophyllus, whose activity did not change with storage even up to 3 days).

INTRODUCTION

MATERIAI~ AND METHODS

Diabetes mellitus is the most c o m m o n endocrine disorder and nearly 25 billion people in the world are affected by it. This clinical syndrome is characterized by hyperglycaemia due to the deficiency or diminished effectiveness of insulin. In Sri-Lanka and India aqueous extracts of several plant species are administered orally to control the blood sugar levels in diabetic patients (Attygale, 1952; Chopra et al., 1958; Said, 1969; Bever and Zahad, 1979; Jayaweera, 1982). Approximately 40 plants available locally are reputed to have oral hypoglycaemic activity. In spite of the fact that these claims have not been scientifically proven, boiled extracts of different parts of these plants, either as single drugs or compound preparations, are prescribed by Ayurvedic physicians in the treatment of diabetes. While the therapeutic efficacy of the these preparations cannot be established without controlled clinical studies, any potential toxicity associated with these preparations cannot also be ruled out. A controlled study of the oral hypoglycaemic activities of Artocarpus heterophyllus Lain. (family Moraceae), Osbeckia octandra D C (family Melastomaceae) and Bambusa vulgaris Linn. (family Graminae) was therefore initiated with a view to establishing scientifically the therapeutic efficacy as well as the most effective dosages of these plant preparations. It is hoped that such an investigation would also help in a more rational use of these plant extracts as drugs to control blood sugar levels. Results of the preliminary investigations carried out on the oral hypoglycaemic activity of these plants are reported here.

Experimental animals In all experiments, male Sprague-Dawley rats of body weight ranging from 125 to 175 g were used and maintained on a standard laboratory diet (natural diet obtained from Moosajee's Ltd, Sri-Lanka) and water ad libitum. The animals were fasted overnight (14-16hr) before the commencement of all experiments. After collecting blood samples for the determination of fasting blood glucose levels, the animals were randomly divided into different groups as required.

*To whom all correspondence should be addressed: Professor M. I. Thabrew, Department of Biochemistry, Faculty of Medicine, University of Ruhuna, P.O. Box 70, Galle, Sri-Lanka.

Dosage and administration of drugs All drugs were administered via a stomach tube. The dosage administered was l0 ml/kg in all instances. Control animals received 10 ml/kg orally of distilled water.

Preparation of drugs The plant extracts were prepared according to the methods normally used by Traditional Medical Practitioners for administration to diabetic patients. The methods quoted in medicinal plant books (Atygall¢, 1952; Jayawcera, 1982) were confirmed by discussions with several well regarded traditional medical practitioners in southern Sri-Lanka. Artocarpus heterophyllus. Fresh mature leaves (200g) were boiled with distilled water (I000 ml) for 3 hr and the final volume reduced to 200 ml. Bambusa vulgaris. Fresh tender leaves (200 g) were boiled with distilled water (1000 ml) for 3 hr and the final volume reduced to 200 ml. Osbeckia octandra. Fresh mature leaves (200g) were boiled with distilled water (1000 ml) for 3 hr and the final volume reduced to 200 ml. The biochemical identity of the plants were determined by using the descriptions of Jayaweera 0982) and confirmed by comparing the authentic samples from the Herbarium of the University of Peradeniya. The plants were collected from Galle in southern Sri-Lanka. Tolbutamide. Tolbutamide (Hoechst Pharmaceuticals Ltd., 500 mg tablet) was finely powdered and 150 mg dispersed in distilled water (100 ml). Before administration the suspension was thoroughly mixed to ensure homogeneity.

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Determination of blood glucose

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Blood samples (0. I ml) were drawn at regular intervals by tail puncture using a microcap (Drummond Scientific Company, U.S.A.) into distilled water (3.5 ml). The proteins were precipitated by adding barium hydroxide (0.2 ml, 10% w/v) and zinc sulphate (0.2mI, 5%w/v). The precipitated proteins were removed by centrifugation and supernatant was collected. The glucose content in the supernatant was assayed by the glucose oxidase method (Hugget and Dixon, 1957).

Effect of drug~" on .fasting blood glucose level Male Sprague Dawley rats (n = 50) were randomly divided into 5 groups of 10 each. Animals in each group were initially fasted overnight. After taking blood samples for the determination of fasting blood glucose, group I was given distilled water (10 ml/kg), group 2 was given A. heterophyllus extract (I0 ml/kg), group 3 was given B. vulgaris extract (10 ml/kg), group 4 was given O. octandra extract (10 ml/kg) and group 5 was given tolbutamide (10ml/kg). Blood samples were collected at I hr intervals post-administration and assayed for glucose.

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Effect o/ drug on glucose tolerance Male SpragueDawley rats (n =40) were randomly divided into 4 groups of 10 each. Each group was fasted overnight. After collecting samples (0.1 ml) of blood, to determine the fasting blood glucose level, group I was given distilled water (10 mg/kg), group 2 was given A. heterophyllus extract (10 mg/kg), group 3 was given B. vulgarL, extract (10ml/kg) and group 4 was given O. octandra extract (10mg/kg). 30min after the administration of drugs, all groups were given an oral dose of glucose (10ml/kg, 50% w/v). Samples of blood were then collected at I hr intervals for 5 hr and blood glucose content estimated as before.

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Time {hr) Fig. 2. The effect of aqueous extracts of Artocarpus hetero(f-l, 10 ml/kg; 10 g/kg), Bambusa vulgaris (O, l0 ml/kg; 10 g/kg) and Osbeckia octandra (A, 10 ml/kg; 10g/kg) on oral glucose tolerance relative to controls (0, 10 ml distilled water/kg). Blood samples were taken at 1 hr intervals. Results were expressed as the percentage increase in the blood glucose level. Each point is the mean of 10 determinations + SEM. When examined by the Student's t-test, significantly different from controls; * P < 0 . 0 5 ; **P < 0.001.

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Dose-resport~e studies o

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In dose-response studies, dosages of 20, 10 and 5 ml plant extract per kilogram body weight were administered to fasting rats (n = 6 in each group) and the variation of fasting blood glucose levels estimated.

Effect of extract storage on biological activity

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The effect of storage on biological activity was studied with the plant extracts prepared as described above. The extracts were stored at room temperature for 24, 48 and 72 hr and the biological activity measured at the end of each stage of storage. RESULTS

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Fig. I. The percent effect of aqueous extracts of Artocarpus heterophyllus ({S], 10ml/kg; 10g/kg); Bambusa vulgaris ( 1 , 10ml/kg; 10g/kg); Osbeckia octandra (A, 10ml/kg; 10g/kg) and tolbutamide (O, 10ml/kg; 15g/kg) on the fasting blood glucose level relative to controls (O, 10 ml/kg of distilled water). Blood samples were taken at 1 hr intervals. Each point is the mean of 10 determinations + SEM. When examined by the Student's t-test, significantly different from control; *P

Hypoglycaemic activity of some medicinal plants in Sri-Lanka.

1. Investigations were carried out to determine whether aqueous extracts of Osbeckia octandra, Artocarpus heterophyllus and Bambusa vulgaris truly pos...
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