Phytochemical, Antimicrobial, and Antioxidant constituents of the stem barks of trichilia monadelpha (thronn) j.j. de wilde and trichilia tessmannii (harms) both of the family meliaceae

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In this present work, the stem barks of two medicinal plants, Trichilia tessmannii (Harms) and Trichilia monadelpha (Thonn) JJ De Wilde both of the family Meliaceae were screened for their phytochemical constituents and evaluated for their antimicrobial and antioxidant activities with the sole objective of isolating the active principles present. The phytochemical investigation revealed the presence of plant secondary metabolites such as; Tannins, Reducing sugars, Anthraquinones, Alkaloids, Saponins glycosides, Cardiac glycosides, Terpinoids, Cumarins and Phytosterol. The antimicrobial activity was determined by broth dilution method using standardized bacteria suspensions of Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa and the fungus, Candida albicans. Broad-spectrum antimicrobial activity was observed for all extracts except the petroleum ether extract of T. tessmannii. A minimum inhibitory concentration (MIC) of 0.625 mg/mL was determined as the highest activity for the ethyl acetate extract of T. tessmannii against Pseudomonas aeruginosa and Candida albicans. Lowest MIC of >10 mg/mL was however recorded by the petroleum ether extract of T. tessmannii against Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa. Antioxidant activity was determined by the use of DPPH free radical scavenging assay, Total phenol content assay and Total antioxidant capacity assay on the total crude methanol extract of the stem bark. The total crude methanol extract was found to possess DPPH free radical scavenging activity of EC50 values 0.0207 mg/mL and 0.0099 mg/mL for the extracts of T. tessmannii and T. monadelpha respectively and 0.004806 mg/mL for the ascorbic acid used as the reference drug. The values obtained from the estimation of the Total antioxidant capacity assay were 444.7 ± 28.58 mg/g of ascorbic acid and 324.40 ± 20.41mg/g of ascorbic acid for T. tessmannii and T. monadelpha respectively, and the Total phenol content values v for T. tessmannii and T. monadelpha were 970.2 ± 78.69 mg/g of tannic acid and 884.2 ± 61.00 mg/g of tannic acid respectively. These findings provide scientific justification for the use of the stem barks of T. tessmannii and T. monadelpha, in various traditional medicines, for the treatment and management of diseases associated with oxidative stress and infectious conditions. The chromatographic separation of extracts done so far was by open column silica gel chromatography using the gradient elution method. Chromatographic separation of the ethyl acetate extract of the stem back of T. Monadelpha (TME) has yielded an isolate ‗A 1 ‘, which is yet to be further purified and characterized.
A thesis submitted in fulfillment of the requirement for the degree of Master of Philosophy in Pharmaceutical Chemistry, 2014