The antimicrobial activity of extracts of the stem bark of Alstonia Boonei De Wild

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The antimicrobial activity of the alkaloidal extract of the stem bark of Aistonia boonei De Wild family Apocynaceae (Synonymous: Alstonia congensis Cher & Anbrev), a Ghanaian medicinal plant used in local folklore medicine has been studied. Both in vitro and in vivo activity studies have been carried out. Preliminary TLC analysis of the less basic fraction (Solution A) gave three spots X, Y, Z, using the solvent system:- chloroform: methanol (9:1). TLC analysis of the strongly basic fraction of the extracts (Solution B) yielded four spots, A’, B’, C’ and D’. The solvent system used for TLC analysis was chloroform: acetone: methanol (11:8:1). Spot D’ on a chloroform: acetone (5:4) solvent system gave two further spots E’ and F’. In vitro and in vivo antimicrobial studies were carried out using the Solutions A and B. Weight by weight, Solution B showed more antimicrobial activity than Solution A. There was in vitro inhibition of growth by both Solution A and Solution B in Streptococcus faecalis, Escherichia coli, Salmonella typhi, Staphylococcus aureus and Bacillus subtilis which were used as test micro organisms. The in vivo study of the extracts from the stem back of Alstonia boonei was performed in both rats and day old chicks infected (by inoculation) with a hospital strain of Staphylococcus aureus H512. All the spots obtained by TLC had antimicrobial activity but spectrum of activity was different. Spots A’, B’, E’ and F’ of solution ‘B’ were effective against all the test micro—organisms. Spots C’ was effective against all the test micro—organisms except Escherichia coli and Salmonella typhi. Spot Y was effective against all the test micro-organisms while Spot X was effective against all the test micro-organisms except Bacillus subtilis. Spot Z however, was effective against only Salmonella typhi. The Solution ‘B” extract was more effective in the elimination of staphylococcus aureus than the Solution ‘A’ in both rats and chicks.
A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirement for the award of the Degree of Master of Pharmacy, 1992