Antiasthmatic and other Pharmacological studies on an aqueous extract from Parquetina Nigrescens (Periplocaceae)

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2000-02-01
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Anti-asthmatic and other pharmacological studies have been carried out on the aqueous extract of Parquetina nigrescens, an anti-asthmatic traditional medical remedy. The extract dose-dependently reduced the contractile effects of histamine and carbachol on the guinea-pig tracheal chain preparation. However, Parquetina induced dose related contractions of isolated guinea-pig ileum (dose ranging 0.024-1 .53 6mg/mI). The contractions were not affected by hexamethonium or mepyramine, but were inhibited by atropine, which implies it was acting on muscarinic receptors, in the ileal preparation. The contractions were also partially abolished in the presence of guinea-pig serum. On the conscious guinea pig, the extract (400 and 800mg/kg) had a protective effect on histamine and antigen-induced broncho spasm comparable to the standard drug, astemizole (0.143mg/kg). The extract in rats, caused inhibition of the increase in the paw size (acute inflammation) induced by subplantar injection of carrageenan suspension. The action of extract was also studied on skeletal muscle preparations of toad rectus abdominis muscle and day old chicks. Farquetina produced neuromuscular blockade of depolarising type; there was also an indication of a direct effect on muscle fibres of the toad rectus abdominis muscle. The LD50 in rats could not be determined after acute administration of 3200mg/kg (LD50> 3200mg/kg). The toxic potential of extract was also assessed by assaying serum activities of γ-glutamyl transferase (GGT), alkaline phosphatase (ALP), alanine amin1otransferase (ALT) and aspartate aminotransferase (AST). Serum bilirubin and urea were also determined. The effect of extract on these parameters is not indicative of damage due to internal organs. This was supported by the histopathological studies which did not show any pathological change in them. Haematological studies showed a slight reduction in haemoglobin concentration as well as red blood cell and white blood cell counts.
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A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirements for the award of Master of Philosophy in Biochemistry, 2000
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