Abstract

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This study was aimed to evaluate the in vitro antimicrobial activities of different solvent extracts of seeds of Garcinia kola (Clusiacea) on some pathogenic bacteria and fungi. The seed was extracted using n-hexane, ethyl acetate, honey, and vinegar as solvents. The in vitro antimicrobial activities of the extracts on Candida albicans, Escherichia coli ATCC 25922, and Staphylococcus aureus ATCC 25923) were assayed using the disc diffusion method. The Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC), and Minimum Fungicidal Concentration (MFC) were evaluated using standard microbiological techniques. Phytochemical components of all the solvent extracts were determined and High-Performance Liquid Chromatography (HPLC) of the organic solvent extracts were further analysed. All the extracts exhibited varying degrees of concentration-based antimicrobial activities against the tested pathogens. The plant exhibited varying degrees of MIC/MFC with values ranging from 100 mg/mL (for n-Hexane extract against E. coli ATCC 25922) for organic solvents, followed 50 µg/mL obtained for honey extract (against E. coli ATCC 25922) and the least MIC value (12.5 µg/mL) was obtained for ethyl acetate (against S. aureus ATCC 25923 and C. albicans, respectively), the combination of solvent extract (against C. albicans) and vinegar (against E. coli ATCC 25922and C. albicans, respectively). The maximum MBC value was obtained for n-Hexane extract (100 µg/mL) and Honey extract (50 µg/mL) against E. coli ATCC 25922, while the least MBC value (25 µg/mL) was obtained for the combination of solvent extracts against S. aureus ATCC 25923 and C. albicans, respectively. Maximum MFC (50 µg/mL) was obtained for n-Hexane, vinegar, and the combination of solvent extracts and the least was n-Hexane. Saponin, tannin, phenolic, flavonoid, coumarin, anthocyanin, steroid, glycosides, triterpenes, phlobatannins amino acids, and alkaloids were randomly present in all the solvent extracts. The HPLC detector measured 13 compounds in the n-hexane extracts, 3 of which were identified at different concentrations Luteolin (96.94 mg/mL), Apigenin (4.43 mg/mL) and quercetin (4.06 mg/mL). A total of 14 compounds were detected in the ethyl acetate extracts, 6 of which were identified as Gallic acid (25.65 mg/mL), theobromine (17.31), caffeic acid (17.02), catechin (16.09), quercetin (8.99), and epicatechin (11.08 mg/mL). This study provides information on the antimicrobial activities and components of G. kola seeds. Also, it contributes to the development of alternative therapeutic agents against the pathogens tested in this study

Keywords: Clusiacea, G. kola, Luteolin, Phlobatanin, Theobromine