The Antimycobacterial Activity, Toxicity and Chemical Composition of South African Propolis

Abstract

Global research has explored the antimicrobial properties of propolis; however, the antimycobacterial activity of South African (SA) propolis has been neglected. This study evaluated 109 propolis samples collected from eight SA provinces where the antimycobacterial activity, chemical composition and toxicity was evaluated. Samples were tested using a broth microdilution assay against various Mycobacterium strains (M. fortuitum ATCC 6841, M. gordonae ATCC 14470 and M. smegmatis ATCC 14468) and the pathogenic M. tuberculosis H37Rv strain. A multi-step approach combining ultra-performance liquid chromatography/ mass spectrometry (UPLC-MS) profiling, high-performance thin-layer chromatography (HPTLC) bio-autography, brine shrimp toxicity testing and molecular docking was employed on eight bio-active and eight non-active propolis samples. Two samples (GP68 and EC77B) demonstrated promising activity, with MICs ranging from 49-195 µg/mL against non-tuberculous strains and 125 µg/mL against M. tuberculosis. Chemometric and bio-autography analyses identified flavonoids and related compounds, including pinocembrin, galangin, chrysin and pinobanksin compounds as major contributors to activity. Both samples were non-toxic at concentrations (1 mg/mL at 24 h; 0.5 mg/mL at 48 h). Molecular docking indicated favourable binding to key M. tuberculosis targets involved in cell wall biosynthesis (DprE1) and transcription (RNAP). This study demonstrates that selected SA-derived propolis samples show strong antimycobacterial potential.