A Study of The Effect of Fractionation on Phytochemical Composition And In Vitro Antimicrobial Activity of Methanol Extract of Garcinia Kola (Heckel) Seeds on Some Bacterial Isolates

Abstract

Objective: The objective of this study is to investigate the effect of fractionation of the crude methanol extract of Garcinia kola (Heckel) seeds on phytochemical constituents and in vitro antimicrobial activity. Method: Fractionation was carried out using the solvent portioning method with solvents of different polarities. Phytochemical analysis was done by use of specific analytical test for each constituent. The minimum inhibitory concentration was determined by the broth microdilution assay while the minimum bactericidal concentration was carried out using the agar well diffusion method. Results: The different fractions exhibited differences in their composition of the phytochemical constituents. This observation was however not dependent on the sequence of the polarity of the solvents. The acetone fraction presented similar phytochemicals compared with those of the crude methanol extract. The n-hexane fraction presented the least phytochemicals. The crude methanol fraction exhibited antibacterial activity against all the isolates at the concentration of 200 mg/ml, suggesting that fractionation may not be of any added advantage on the antibacterial activity. The antibacterial activity exhibited by the fractions against all the isolates were significant lower compared to that due to the standard antibiotic, gentamicin, 4 mg/ml (P < 0.05). Similarly, it was shown that the antibacterial activity of each of the fraction was dose-dependent, with larger zones of inhibition corresponding to higher concentrations (P < 0.05). The acetone fraction exhibited highest antibacterial activity on S aureus with a zone of inhibition of inhibition of 20.5 ± 7.1 mm at the concentration of 200 mg/ml. This was significantly lower compared to 31.5 ± 6.2 mm due to gentamicin, 4 mg/ml (P < 0.05). The lowest antibacterial activity was exhibited at 200 mg/ml was seen with the methanol fraction on E coli with a zone of inhibition of 4.3 ± 1.2 mm and it was the only fraction with effect against this isolate. The n-hexane fraction did not exhibit any visible antimicrobial activity on all the isolates. Conclusion: Fractionation of the crude methanol extract revealed the antibacterial activity of the fractions with the acetone fraction more effective on S aureus than the crude extract. The finding generally confirms and validate the traditional claims and other scientific findings that Garcinia kola possesses principles that are antibacterial. This could therefore justify its traditional use in some infectious diseases and the need for further investigations.