Phytochemical Investigation and Bioactivity Assessment of Medicinal Plant from Northern Nigeria
Boswellia dalzielii (Burseraceae) has ethnopharmacological importance and is claimed to have anti-infection and immunomodulatory effects. In the Northern part of Nigeria, a region with a tropical dry climate, an aqueous infusion of this plant is used in the treatment of infections and tumours. The traditional formulation method was mimicked under laboratory conditions, and the effect of temperature and the impact of endophytic microbes present in aqueous infusion of B. dalzielii was also investigated. Activity-guided fractionation against Staphylococcus aureus and its methicillin-resistant strain resulted in the identification of two antibacterial compounds namely gallic acid and pyrogallol. The Minimum Inhibitory Concentration for pyrogallol and gallic acid against S. aureus growth are 508 and 753 μM, while against MRSA growth are 254 and 2032 μM, respectively. A growth Inhibition assay showed the activity of gallic acid as bacteriostatic, and pyrogallol as bacteriocidal against tested microorganisms. Interestingly, the bacteriocidal compound was found to arise by conversion of gallic acid by the endophyte Enterobacter cloacae. In addition, Pantoea spp was also isolated from the bark of B. Dalzielii. The sequences of both E. cloacae and Pantoea spp are deposited in the GenBank nucleotide database under the accession number MH764584 and MH764583, respectively. Similarly, activity-guided fractionation of B. Dalzielii bark against breast cancer cell line (MCF7) using MTT cytotoxicity assay resulted in the identification of a cytotoxic compound, catechol, and the half maximal effective concentration (EC50) observed was 86μM. The growth inhibition effect of catechol was observed to be time- and concentration- dependent. Endophytic Klebsiella pneumonia species (strain A and B) were shown to be responsible for bioconversion of protocatechuic acid to catechol. In addition, Pantoea agglomerans was also isolated from the bark of B. dalzielii. The sequences of Klebsiella pneumonia A, Klebsiella pneumonia B and Pantoea agglomerans are deposited in the GenBank nucleotide database under the accession number MH762022, MH762023 and MH762024, respectively. All isolated compounds were identified using HPLC, TLC, NMR, FTIR and HRMS.
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