ANTIBACTERIAL ACTIVITIES AND PHYTOCHEMICAL COMPOSITION OF STEM BARK AND SEEDS EXTRACTS OF THREE BOTANICALS ON THREE SELECTED PATHOGENIC BACTERIA

Abstract

ABSTRACT The increasing rate of development of resistance to commonly used antibiotics have necessitates the need to re-evaluate some of the plants that have been previously studied due to changes in ecosystem and geographical variations. The aim of this study was to investigate the antibacterial activities and phytochemical constituents of Boswella dalzielii (stem), Enantia chlorantha (stem), and Abrus precatorius (seeds) extract. The plant materials were extracted using cold merceration technique and weight percentage yield were recorded for each plant extract. The plants extracts were prepared at different concentration of 50, 100, 150, 200, 250, and 300 mg/ml against Escherichia coli, Pseudomonas aeruginosa and Salmonella bongori. Antibacterial activity and quantitative phytochemical analysis of the extracts were carried out using agar well diffusion method and spectrophotometry respectively. Bioactive compounds present in the fractions were determined using Gas ChromatographyMass Spectrometry (GC-MS). The minimum inhibitory concentrations (MICs) and minimum bactericidal concentration (MBC) of the extracts and fractions were also determined using the broth micro-tube dilution technique. A significant antibacterial activity was observed against E. coli for B. dalzielii stem (7.50±0.00-18.45±00.25 mm), E. chlorantha stem (5.35±0.65-15.90±0.10 mm), and A. precatorius seed (8.75±0.25-14.00±1.00 mm) and the lowest activity was observed against P. aeruginosa for the three plant 6.70±0.30-12.80±0.20, 4.15±1.15-5.60±0.40, 9.80±0.50 mm respectively. The n-Hexane fraction shows a narrow zone of inhibition for all the three plants extract, the aqueous fraction has a significant activity against E. coli for B. dalzielii stem (11.50±1.50-19.50±0.50 mm), E. chlorantha stem (5.55±0.45-15.50±45.5 mm) and A. precatorius seed (7.75±1.25-12.60±0.40 mm) and a minimal activity was observed against P. aeruginosa for the three plant extracts as 8.50±0.50-11.50±0.50mm, 8.55±1.55-11.75mm, 4.50±0.30-6.90±0.10mm respectively. The ethyl acetate fraction was observed to have a significant activity against E. coli for B. dalzielii stem (9.00±1.00-17.50±0.50mm), E. chlorantha stem (5.40±1.05-10.05±0.05mm) and A. precatorius seed (5.95±0.50-6.95±0.25mm). The MIC and MBC of the extract ranged between 35.5 to 300 mg/mL against the bacterial isolates. The GC-MS analysis of the B. dalzielii fraction revealed 6 compounds for aqueous fraction, 6 compounds for ethyl acetate and 5 compound for n-Hexane with 9,12-octadecadienoic acid (z,z)-,2,3-dihydroxypropyl (50.05%), 9,12octadecadienoic acid (z,z)- (20.50) and 9,12-octadecadienoic acid (z,z)- (5.46%) with the highest concentration respectively. 5 compounds for A. precatorius with 1,2,3Benzenetriol (ethylacetate fraction at 30.83%) and 1,5-anhydro-d-mannitol (residual aqueous fraction at 31.77%) with the highest concentration respectively and 4 compounds for E. chloranta with 9,12-octadecadienoic acid (z,z)-2,3dihydroxypropyl (ethylacetate fraction at 28.05%) had the highest concentration. The quantitative phytochemical screening of the plants extracts revealed the presences of phenols, flavonoids, saponins, alkaloids and tannins with highest phenol content observed with B. dalzielii (989.04±0.60) and the lowest was observed with E. chlorantha (416.07±0.07). The extracts of stem bark of Boswella dalzielii, A. precatorius seed and E. chlorantha stem barks exhibited antibacterial and contained many active compounds.