Determination of Phytochemicals and Antimicrobial Activity of Aqueous Stem Bark Extract of Boswellia dalzielii against Some Common Pathogenic Microorganisms

Abstract

Phytochemical screening by High-Performance Liquid Chromatography (HPLC), Fourier Transform Infrared Spectroscopy (FTIR), and Gas Chromatography-Mass Spectrometry (GC-MS) of the crude aqueous extract of the stem bark of B. dalzielii was performed, and its antimicrobial activity on Staphylococcus aureus, Streptococcus pyogenes, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Proteus mirabilis, Salmonella typhi, and Candida albicans was evaluated. The HPLC analysis revealed 10 components, with major peaks at 3, 2, 4, 5, 8, and 6, having peak areas of 33.43%, 13.75%, 13.43%, 9.35%, 8.53%, and 8.50%, respectively. FTIR analysis identified 18 functional groups, including amines, amides, α,β-unsaturated aldehydes, ketones, alkanes, alkenes, alkynes, alkyl halides, aromatics, and aromatic and aliphatic amines. GC-MS analysis revealed 9 compounds, with the major ones being n-Hexadecanoic acid, Stearic acid, 9-Hexadecenoic acid, and 1,E-11,Z-13-Octadecatriene, with peak areas of 39.40%, 24.28%, 23.38%, and 7.73%, respectively. The susceptibility test showed that the extract, at concentrations ranging from 50 mg/ml to 5 mg/ml, was active against all the test isolates. The highest zones of inhibition were observed for S. typhi (19 ± 0.00 mm), P. mirabilis (18 ± 0.30 mm), and P. aeruginosa (18 ± 0.41 mm) at 50 mg/ml concentration. Resistance was observed in E. coli and S. pyogenes at 2.5 mg/ml concentration. The lowest MIC values of 12.5 mg/ml were recorded for S. typhi and S. aureus, while 25 mg/ml MIC values were observed for C. albicans, P. mirabilis, and P. aeruginosa. K. pneumoniae, E. coli, S. pyogenes, and E. faecalis had MIC values of 50 mg/ml each. The MBC/MFC values did not exceed the corresponding MIC values by more than a factor of 2. Conclusively, the stem bark of B. dalzielii contains numerous antimicrobial active compounds that can be purified and potentially used as precursors for developing new antibiotics.