Studies on some pharmacologic and toxic properties of Peddiae Volkensii Gilg and Scutia Myrtina

Abstract

Peddlae volkensil dig and Scutla myrtina (Burin.f.) Kurz have been used medicinally as laxatives, and have also been said to be toxic. One aim of the research reported in this thesis was to test whether methanol extracts of the dried leaves from the two plants had stimulatory effects on the smooth muscles of the rabbit duodenum and the effects of the various drugs that would block the stimulatory effect if present. The second aim was to test the effects of the above named extracts on the blood pressure in an anaesthetised dog and the effects of drugs that block the observed effects. The third aim was to observe the toxicity and clinicopathologic signs in rats fed rations containing ground dried leaves of the two plants for 90 days. The last aim was to determine the median lethal dose (LD_^) of the freeze dried extracts of the leaves in mice injected intraperitoneally. The clinical signs observed in 40 rate fed P. volkensil dig and 36 rats fed 3. myrtina (Burm.f.) Kurz, included rough hair coats diarrhoea in all rats and weight loss in many. For rats fed P. volkensil dig, the liver weight* body weight ratio was less compared to the control group. This was an indication of liver cell damage, a fact shown histologically. The rats fed P. volkensil Gilg had marked hydroperitoneum hydrothorax and frothy trachea. There were no significant gross findings in rats fed S. myrtina (Burm.f.) Kurz. Microscopically, both plants produced pulmonary haemorrhages and severe alveolar thickening, P. volkensli Gilg also caused renal proximal convoluted cellular degeneration, hepatic and adrenal cortical haemorrhages, marked splenic hemosiderosis signifying increased red blood cell destruction. Methanol extract of P. volkensil Gilg leaves caused a piece of rabbit duodenum to decrease in rate of rhythmic contractions, but increase in the tone and force of contractions. Pretreatment of the preparation with atropine had no effect on the activity of the extract. This suggests that the mechanism of stimulation was not cholinergic since atropine is a blocker of the muscarinic receptors of acetylcholine. Pretreatment of the preparation with mepyramine maleate blocked the stimulatory effects of the extract which suggests histamine-like properties since mepyramine maleate is a blocker of histamine receptors. Methanol extract of 3. myrtina (Burm.f.) Kurz produced increased force but decreased rate and tone of rabbit duodenum. Pretreatment with mepyramine maleate produced no change in the effects of the extract except that there was no increased force of contractions. This was possibly clue to the anticholinergic properties of mepyramine maleate. Pretreatment with 1 mg atropine sulphate completely abolished the stimulatory effect of the extract,' This suggests that the stimulatory effect was cholinergic in nature, P. volkensii Gilg methanol extract caused a decrease in the blood pressure in the dog. The systolic, diastolic and the pulse pressures were decreased. The heart rate was also increased possibly by baroreceptor mechanism, Pretrea- tment with propranalol, mepyramine maleate and atropine was inconclusive. In case of myrtina (Burm.f.) Kurz methanol extract, the effect on the blood pressure in the dog was as in P. volkensii Gilg, i.e. an overall decrease in blood pressure. However, pretreatment with mepyramine maleate blocked the decrease in blood pressure by about 75$, while pretreatment with atropine sulphate blocked the decrease in blood pressure by about 100$, This suggests that . myrtlna (Burm.f.) Kurz caused a decrease in blood pressure by both cholinergic and histamine-like mechanisms. In conclusion, both P. volkensii Gilg and S. mvrtlna (Burm.f.) Kurz stimulate rabbit duodenum, decrease systolic, diastolic and pulse pressure in the dog which suggest they could be used as laxatives and antihypertensives. However, this is not advisable because both plants produce pulmonary haemorrhages and severe alveolar thickening. P. volkensii Gilg also cause renal proximal convoluted cellular degeneration, hepatic and adrenal cortical haemorrhages and marked splenic hemosiderosis signifying red blood cell destruction. The acute (24 hr) LD,-0 for myrtina (Burm.f.) Kurz is (6.1) g/kg and that of P. volkensii Gilg is (6.3) g/kg of body weight in mice.