Bioactivity guided isolation and characterization of the antimicrobial constituents of Mammea Africana S. (Guttiferae) and Spathodea Campanulata B. (Bignoniaceae)

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Investigation has been conducted on the stem-bark of Mammea africana (Guttiferae) and Spathodea campanulata (Bignoniaceae), reputable medicinal plants that are used in traditional medicine for treating various infectious conditions such as boils, infected wounds and ulcers. The aim was to establish the scientific basis for their use and also to isolate some of the compounds responsible for the antimicrobial activity. These plants are found in tropical Africa including Ghana where they are found in the deciduous forest of the Ashanti Region. The ethanolic and petroleum ether extracts from the stem bark of M africana showed antibacterial activity against Escherichia coli, Bacillus subtillis, Pseudomonas aeruginosa, Clostridium histolyticum and Staphylococcus aureus. Four coumarins, one of which was characterized as mammea B/BA, were isolated by chromatography from the petroleum ether extract of this plant. These compounds showed antibacterial activity against the above-mentioned bacteria. Their activity against Candida albicans was, however, negligible. The ethanolie extract also yielded the ubiquitous plant sterols, 13-sitosterol and stigmasterol. The petroleum ether, ethyl acetate and ethanolic extracts of the stem bark of S. campanulata also showed significant activity against the above-mentioned bacteria. In addition these extracts showed activity against the yeast-like fungi, Candida albicans. The various chromatographic fractions obtained from the ethyl acetate and petroleum ether extracts also showed varying activities against the micro-organisms. Though no compound was characterised from S. campanulata the extracts and their fractions showed antimicrobi& activities which validates its use in the treatment of some infectious conditions.
A thesis submitted to the Department of Pharmacognosy, College of Health Sciences in partial fulfilment of the requirements for the degree of Master of Science, 2004