Oral hypoglycaemic activity of some medicinal plants of Sri Lanka

Journal of Ethnopharmacology, 11 (1984) Elsevier Scientific Publishers Ireland Ltd.

ORAL HYPOGLYCAEMIC OF SRI LANKA

E.H. KARUNANAYAKE, SINNADORAI

ACTIVITY

J. WELIHINDA.

Department of Biochemistry, Colombo 8 (Sri Lanka)

223

223-231

OF SOME MEDICINAL PLANTS

S.R. SIRIMANNE and GOWRI

Faculty of Medicine,

University of Colombo,

Kynsey

Road,

(Accepted May 2, 1984)

summary Investigations were carried out to evaluate the oral hypoglycaemic activity of some Sri Lankan medicinal plants. Approximately 40 plants available locally are reputed to have oral hypoglycaemic activity. Of these, the mostly widely used are (a) Sulacia reticulata (Celastraceae) (b) Aegle marmeh (Rutaceae) and (c) Momordica charantia (Cucurbitaceae). Aqueous decoctions of these plants were investigated for their ability to lower the fasting blood glucose level and improve the glucose tolerance in laboratory animals. The results indicate that the aqueous decoctions of all three plants possess significant hypoglycaemic effect. The magnitude of this effect showed time related variation with the three plants. The highest oral hypoglycaemic activity and the maximum improvement of the oral glucose tolerance were associated with the extract of Momordica charantia while the least but significant effects were shown by Salacia reticulata.

Introduction Aqueous decoctions of plants have been used in the treatment of disease since ancient times. Diabetes mellitus has been no exception and in several countries including Sri Lanka and India, aqueous extracts of several plants species are administered orally to control this disease (Attygalle, 1917; Bever and Zahnd, 1979; Chopra et al., 1958; Farnsworth and Segehnan, 1971; Said, 1969). Inspite 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 these preparations cannot be established without controlled clinical studies, any potential toxicity associated with these preparations cannot also be ruled out. 0378-8741/84/$03.00

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From an economic point of view, the government of Sri Lanka spends a considerable amount of foreign exchange to import orally active hypoglycaemic agents such as sulphonyl ureas and biguanides, in addition to the large stocks of insulin imported. These considerations, together with the possibility that a proper scientific evaluation of their efficacy may help in more rational use of these drugs of plant origin and also the fact that such studies may contribute towards the development of Ayurvedic system of medicine, led us to investigate the oral hypoglycaemic activity of plants used in Ayurvedic medicine in Sri Lanka. Approximately 40 plants available locally are reputed to have oral hypoglycaemic activity when administered in the form of aqueous decoctions (Attygalle, 1917). Of these, the most widely used are (a) Salacia reticulato Weight (Family, Celastraceae; Sinhala, Kothala himbutu; part used, roots). (b) Aegie marme~~s Linn. (Family, Rutaceae; Sinhala, Beli; part used, roots). (c) ~o~o~~~ c~aranti~ Linn. (Family, Cucurbitaceae; Sinhaia, Karawila; part used, fruits). The preliminary investigations carried out on the oral hypoglycaemic activity of these plants are reported here. Mate&Is and methods Experimental

animals

In all experiments male Sprague-Dawley rats of body weight 200 + 25 g, maintained on a standard laboratory diet were used. The animals were fasted overnight (14-16 h) before the commencement of all experiments. After collecting blood samples for the dete~inatio~ of fasting blood glucose levels, the animals were randomly divided into different groups as required. Frepamtion

of drugs

All drugs were prepared according to the method by which they are made for admin~~tion to diabetic patients (Attygalle, 1917). Salacia reticubta Dried and powered root bark (250 g) of the plant was boiled with distilled water (1000 ml) for 3 h and the final volume was reduced to 100 ml in vacua . Aegle marmelos Dried and powered root bark (250 g) was boiled with distilled water (1000 ml) for 3 h and the final volume was reduced to 100 ml in vacua.

Fresh fruits (250 g) were taken and seeds were removed. The fleshy part

225

was cut product at 5000 100 ml)

into small pieces and mascerated with a mortar and pestle. The was squeezed through a muslin cloth and the liquid centrifuged rev./min for 30 min under refrigeration. The supernatant (approx. was used in the investigation.

Dosage and administration

of drugs

In preliminary investigations, all drugs were administered via a stomach tube while the animal was under light diethyl ether anaesthesia. The dosage administered was 1 ml/100 g body wt. Determination

of blood glucose

Blood samples (0.1 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 (0.2 ml, 5% w/v). The precipitated proteins were removed by centrifugation and the supernatant was collected. The glucose content in the supematant was assayed by glucose-oxidase method (Hugget and Nixon, 1957). Effect

of drugs on fasting blood glucose

level

In these studies, animals (n = 24) were fasted overnight. After taking blood samples for the determination of fasting blood glucose level, animals were randomly divided into four groups of six each. Group one was given saline (1 ml/100 g body wt) and groups 2,3 and 4 were given the three preparations of the drugs, respectively. Blood samples were collected at l-h intervals post administration and assayed for glucose as previously described. Effect

of drugs on Glucose

Tolerance

Test (GTT)

Animals (n = 18) were fasted overnight. After collecting samples (0.1 ml) of blood, animals were randomly divided into three groups of six each. Group 1 was given saline (1 ml/100 g body wt) and groups 2 and 3 were given (1 ml/100 g body wt) the extracts of Aegle marmelos and Momordica charantia, respectively. Thirty minutes after the administration of drugs, all groups were given an oral dose of glucose (1 ml/100 g body wt, 50% w/v). Samples of blood were then collected at l-h intervals for 5 h and blood glucose content estimated. Dose-response

studies

In dose response studies, dosages used were 1 ml, 0.5 ml and 0.25 per 100 g body wt, respectively.

ml

226

Effect

of storage of extract

on biological

activity

The effect of storage on biological activity was carried out with the extract of Aegle marmelos. The drug prepared as described previously was stored at room temperature for 24 h, 48 h and 72 h and the hypoglycaemic activity was measured at each stage of storage. Results and discussion extracts of Aegle marmelos, Momordica charantia and showed significant hypoglycaemic activity when compared with the control group of animals receiving an equal dose of saline. With the extracts of Aegle marmelos and Salacia reticulata the maximum hypoglycaemic activity (44% and 30% reduction, respectively) was observed 3 h after the administration of the extracts (Fig. 1). In cpntrast, with Momordica charantia, the maximum effect (45% of reduction) was observed 4 h following the administration of the drug. The extracts of Aegle marmelos and The aqueous

Salacia reticulata

A

of Aegle marmelos, Momordica charantia and Salacia levels. Rats (n = 6) were orally administered 1 ml/ 100 g body wt of each of the extracts. Blood samples (0.1 ml) were taken at l-h intervals and assayed for glucose. The results are given as percentage increase/decrease of glucose/ 100 ml blood. The S.E.M. values are given by the bars. -0, control group; -3, Fig. 1. Effect

reticulato

of aqueous

extracts

on fasting blood glucose

Salacia reticulata;

-A,

Aegle marmelos;

o----o,

Momordica

charantia.

227

Momordica

charantia showed significant (42% and 38% of reduction, respectively) hypoglycaemic activity even at 5 h. Although we have not investigated beyond 5 h, the results may suggest that the effect of Aegle marmelos and Momordica charantia persist for a period longer than 5 h whereas with Salacia reticulata the response seems to be effective up to about 5 h only. The results of the effect of aqueous extracts on oral glucose tolerance are illustrated in Fig. 2. The results are given as percentage increase of fasting A

c I I

I 2

I 3 TIME IN HOURS

I

4

I 5

>

Fig. 2. Effect of aqueous extracts of Aegle marmelos and Momordica charantia on oral glucose tolerance test. Rats (n = 6) were administered 1 ml/100 g body wt of saline or drugs. Blood samples (0.1 ml) were taken at l-h intervals and assayed for glucose. The results are given as percentage increase/100 ml blood. The S.E.M. values are given by bars. -A, control -0, Aegle marmelos; -0, Momordica charantia.

228

blood glucose level. In the control group of animals receiving saline (1 ml/ 100 g body wt), followed 0.5 h later by an oral dose of glucose (1 ml/l00 g body wt), the peak increase in blood glucose concentration (110 ? 10) was observed after 1 h. The blood glucose concentration remained high over the next 3 h. In contrast, the groups receiving the extracts of either Angle marmelos or ~omordica charantia showed significant improvements in their ability to utilise the external glucose load. The group treated with the extract of Aegle marmelos showed only 70% increase in blood glucose concentration after 1 h. This value was 40% less than the peak value attained by the control group during the same period. The most remarkable effect on the glucose tolerance was, however, shown by the extract of Momordica chura~t~. This group registered only an increase of 10% after 1 h, which was 100% less than the peak value in the control group. The increase at ‘2 h was only 22%, a reduction of 78% from the control group. Over the next 3 h, the blood glucose concentration of this group remained fairly constant, showing only an average increase of 13% from the fasting value. Here again

TIME

IN HOURS

a___

_n_

-_---xl

Fig. 3. Effect of different dosages of the extract of Aegle marmelos and Momordica charantia on fasting blood glucose levels. Rats (n = 6) were given 0.25 ml, 0.5 ml and 1 ml/l00 g body wt of respective extracts. Blood samples (0.1 ml) were taken at l-h intervals and assayed for glucose. The results are given as percentage reduction/increase of glucose/100 ml of blood. The S.E.M. values are given by bars. o-----o, 0.25 ml/100 g s----s, 0.5 ml/100 g; +---a, Aegle marmelos; - - - - - Momordica 1.0 ml/100 g; charantia.

229

this slight increase was approximately 25% less than the average value of the control group. These data while confirming our previous results (Welihinda et al., 1981) are also in agreement with the beneficial effect of ~orn~r~ica charantia in diabetes mellitus (Leatherdale et al., 1981). The different responses obtained by varying dosages of aqueous extracts Aegle rn~~e~~ and ~omor~~a c~a~a~t~a are shown in Fig. 3. The results indicate that with both extracts, the maximum hypoglycaemic response though variable in time and magnitude, was associated with a dosage of 1 ml/100 g body wt. With the lowest dosage used (0.25 ml/100 g body wt) higher hypoglycaemic response was observed with the extract of ~o~ur~~cu charantiu. The activities associated with 0.5 ml and 1 ml/l00 g body wt were comparable with the two drugs. It is also noteworthy that the hypoglycaemic activity was not halved as a result of halving the dosages. The effect of storage at room temperature on the hypogly~aemic activity of aqueous extract of Aegle marmebs is illustrated in Fig. 4. The examination of these data indicates a gradual decline in biological activity with storage. After 72 h of storage, the rn~~~ h~~ly~aemic response was only 12% and this was a 66% reduction from the maximum response observed after 24 h of storage. This loss of biological activity may be due either to bacterial action or some other unknown mechanism. However, this

Fig. 4. Effect of storage of the aqueous extract of Aegle marmelos on hypoglycaemic activity. Rats (n = 6) were administered 1 ml/l00 g body wt of the extract of Aegle marmelos, 24 h, 48 h and 72 h after preparation. Blood samples were taken at l-h intervals and assayed for glucose. The results are given as percentage decrease of blood glucose/ 24 h; o-----J 48 h; -rr------0 72 h. 100 ml. The S.E.M. values are given by bars. -A

230

observation strongly supports the advice of Ayurvedic physicians, who insist on daily preparation of the decoctions for oral administration. Of the three extracts investigated, the juice obtained from the fruits of ~o~o~d~ca chara~tia showed the most profound effect both on the fasting blood glucose level and on the ability to tolerate an external glucose load. The fact that this extract was obtained directly from the fruits without the addition of water may account for this high activity. However, in the light of fact that the extracts of Aegle marmelos and Momordica charantia both exhibited comparable effects on fasting blood glucose level (Fig. I), while the effect of Momord~a ~h~ru~tiu on the glucose tolerance was sign~ic~tly higher than Aegle marmelos (Fig. 2), may suggest that Momordica charuntia is more effective in controlling the blood glucose level following a heavy carbohydrate diet. Alternatively, the extracts of Aegle marmelos and Salacia reticulata may be useful in controlling the blood glucose level in mild diabetes, while Momord~cu charantiu may be more useful in the treatment of severe diabetes. The overall results of the present studies are indicative of a highly potent hypoglycaemic activity associated with the aqueous extracts of the root bark of-Aegle marmelos, Salacia reticulata and the extracts of the fruits of Momordica charantia. Although in the present studies, the effect of these extracts have not been compared with a standard oral hypoglycaemic agent, the data provide strong evidence in support of an effective oral hypoglycaemic activity associated with each of the extracts investigated. The most pronounced ability of the extract of the fruits of Momordica charantia to improve the utilization of glucose following an external glucose load, may throw some light on the possible mechanism of hypoglycaemic activity of this drug. Thus, this extract while directly ~~ulat~g the B-cells of the Islets of Langerhans to secrete more insulin, may also facilitate peripheral utilization of glucose, either by direct stimulation of glucose uptake or via the mediation of enhanced insulin secretion. The latter effect may play a more significant role in the adipose tissue. The possibility of the extract interacting directly with the B cells of pancreas is further supported by recent in vitro studies (~el~inda et al., 1982). Acknowledgements This work was supported by Grant No. RG/77/31 from the Natural Resources, Energy & Science Authority of Sri Lanka and partly by Grant No. 531 from the Internation~ Foundation for Science, Sweden. The authors wish to thank Prof. K. Balasubramaniam for his constant interest in this work. References Attygalle, J. (1917) ~~nhalege Materia Medica, Apothecaries Press, Colombo, Sri Lanka. Oliver Bever, B. and Zahnd, G.R. (1979) Quarterly Journal of Crude Dmg Research 17.139-196.

231 Chopra, R.N., Chopra, I.C., Handa, K.L. and Kapur, L.D. (1958) Indigenous Drugs of India, U.N. Dhur & Sons pvt. Ltd., Calcutta, India. Farnsworth, N.R. and Segelman, B. (1971) Tile & Till 57, 52-55. Hugget, A. St. G. and Nixon, D.A. (1957) Lancet 2, 368-370. Leatherdale, B.A., Paneskar, R.K., Singh, G., Atkins, T.W.A., Bailey, C.J. and Bignell, A.H.G. (1981) British Medical Journal 282, 1823-1824. Said, M. (1969) Hamdard Pharmacopoeia of E&tern Medicine, 42pp. Hamdard National Foundation, Times Press, Karahchi, Pakistan. Welihinda, J., Karunanayake, E.H. and Balasubramaniam, K. (1981)Proceedings of the Institute of Chemistry (Sri Lanka) Part I, 16-M. Welihinda, J., Arvidson, G., Gulfe, E., Hellman, B. and Karlsson, E. (1982) Acta Biologica et Medico Germanica 1224-1240.