Phytochemical Determination and In Vitro Antimicrobial Activity of Crude Ethanolic Extract of Stem Bark of Boswellia dalzielii

Background Boswellia dalzielii is a medicinal plant widely used in the traditional treatments of Rheumatism, Septic sores, venereal diseases and gastrointestinal ailments. However, the scientific evaluations of the ethanopharmacological claims of the plant have not been adequately resolved. Aim To carryout automated phytochemical screening and determination of the in vitro antimicrobial activity of the crude ethanolic stem bark extract of B. dalzielii on some common pathogenic microorganisms which included Staphylococcus aureus, Streptococcus pyogenes, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Proteus mirabilis, Salmonella typhi and Candida albicans Methods Fifty grams (50g) of the dried powder of the stem bark of the plant was extracted exhaustively in 500ml of 95 % ethanol by percolation method for two weeks. Phytochemical screening of the extract was performed using High Performance Liquid Chromatography (HPLC), Fourier Transformed Infrared Spectroscopy (FTIR) and Gas Chromatography-Mass Spectrometry (GCMS) after which its antimicrobial activity was evaluated by agar well diffusion method. The minimum inhibitory concentrations (MICs) and minimum bactericidal concentration (MBC) / Minimum Fungicidal concentration (MFC) were also determined using the broth micro-tube dilution technique. Results The HPLC analysis revealed the presence of 8 components with major ones at peaks 3, 4, 5 and 2 with peak areas of 31.52 %, 21.96 %, 17.23 % and 16.21 % respectively, the FT-IR spectroscopy revealed 11 functional groups which included 1, 2 amines and amides, alkanes, alkenes, alkynes, alkyl halides, aromatics and aliphatic amines, while the GCMS analysis revealed 13 compounds and the major ones were n-Hexadecanoic acid (23.54 %), Oxacyclotetradecan-2-one (20.33 %), Pelargic acid (16.83 %), n-Eicosanol (13.51 %) and Ethyl striate (10.05 %). Several studies reported that these compounds have antimicrobial, anticancer and anti-oxidant activities except n-Eicosanol and Ethyl steriate which are highly toxic. The susceptibility test showed that the extract was active against all the test isolates with higher zones of inhibition of 210.00mm for C. albicans and S. typhi, 200.80mm for S. aureus, and 190.50mm for K. Pneumoniae, 180.80mm for E. coli and 180.80mm for P. aeruginosa at 50mg/ml concentration each. Resistance was only observed at 2.5mg/ml concentration for S. pyogenes. Similarly, lowest MIC values of 3.12mg/ml were obtained for C. albicans and S. typhi, 6.25mg/ml for S. aureus, 12.5mg/ml for K. Pneumoniae, E. faecalis and P. mirabilis, 25mg/ml for E. coli and S. pyogenes and the highest MIC of 50mg/ml for P. aeruginosa. The MBC/MFC values did not exceed the corresponding MIC values by more than a factor of 2. Conclusion Although the stem bark of B. dalzielii showed strong antibacterial and antifungal activity and contained many antimicrobially active compounds, it also contained potentially toxic components and hence adequate toxicological data is needed to validate the safety of the stem bark of this plant for consumption.