Bioactivity guided isolation and characterisation of the antimicrobial principles of Mammea Africana S. (Guttiferae)

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This thesis is a report on the bioactivity guided isolation and characterisation of the antimicrobial principles of Mammea africana S. (Guttiferae) a large evergreen tree found in the tropical rain forest of Ghana, specifically in the wetter mixed deciduous forest of Ashanti Region. Mammea africana is known throughout the tropics and subtropics and is used to treat dermal infections like boils, itches and crawcraw. It is also used in the treatment of rheumatic pain, whooping cough and to cleanse ulcers. The study has shown that the bark of Mammea africana exhibits antimicrobial properties in vitro. Preliminary bloactivity studies of the crude ethanollc extract showed activity on test organisms. A petroleum ether fraction that was obtained by fractionation from the crude ethanolic extract also showed tremendous activity on test organisms - as demonstrated by the values of the zones of inhibition. The aqueous fraction left after the extraction with the petroleum ether, however, had no activity. Preliminary TLC analysis of the petroleum ether fraction showed four constituents all of which were isolated by column chromatography and tested for their activities on the test organisms. The third major constituent, Mammea B/BB (R1) was found to be the most active. The three other compounds designated as R2, R3 and R4 were established to be coumarins.R2, R3 and R4 could not be further identified due to paucity of data. They were found to have varying degrees of antimicrobial activity on test organisms though weaker than Mammea B/BB. Comparing their MIC values, R2 was the most active, followed by R3 and R4.
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 Master of Science in Pharmacy, 2000