Phytochemical and <i>in-vitro</i> antibacterial effects of the partitioned portions of <i>Bauhinia rufescens</i> Lam stem bark extract

Abstract

The study into the chemical contents and in-vitro antibacterial effects of the portioned portions of the methanol stem bark extracts of Bauhinia rufescens Lam were evaluated in some Gram positive and Gram negative bacteria using the hole-in-plate disc diffusion technique. The methanol stem bark extract was successively portioned using solvents of grade polarities: n-hexane, chloroform, ethylacetate, n-butanol and water. Qualitative phytochemical components of these portions were determined using conventional protocol and the overall results indicated the presence of flavonoids, saponins, resins, cardiac glycosides, cardenolides, aloes, anthraquinones and phlobatannins in one or more of the portions. Test microorganisms include Bacillus subtilis and Streptococcus pneumoniae (Gram positive); Escherichia coli, Klebsiella spp. and Salmonella typhi (Gram negative) bacteria. The diameters of inhibition zone on the Gram positive bacteria was found in the range of 10.33 ± 0.17 (residual aqueous portion) to 28.00 ± 1.00 (n-butanol portion) while on Gram negative organism the values ranged from 10.83 ± 0.17 (residual aqueous portion) to 29.33 ± 0.17 (chloroform portion). The results revealed that most of the portions were highly sensitive on S. typhi with highest MIC/MBC values of 0.78/1.56 mg/ml (n-hexane and ethylacetate portions) and also 1.56/3.13 mg/ml (chloroform and n-butanol portions). The extracts showed equal MIC/MBC data of 1.56 mg/ml on B. subtilis exhibited by n-hexane, ethylacetate and n-butanol portions. The activity index (AI) showed that all the portions were more sensitive to S. pneumoniae and E. coli when computed with erythromycin and Gentamicin respectively. N-butanol portion had the highest AI against B. subtilis (77.90 %), S. pneumoniae (69.86 %) and S. typhi (57.62 %); chloroform recorded higher AI against E. coli (91.74 %) while ethylacetate portion had AI of 88.63 % against Klebsiella spp. when computed with ciprofloxacin. These portions were found to be more sensitive to Gram negative than gram positive species studied. The study further confirms the use of the part of B. rufescens in some parts of Northern Nigeria as a remedy against diarrhoea, dysentery and other related diseases whose causative agents are most of the organisms tested.

Keywords: Bauhinia rufescens, organic portions, phytochemical, antibacterial, stem bark, in-vitro.