Antioxidant: Antimycobacterial and Antibiofilm Activities of Acetone Extract and Subfraction Artemisia afra Jacq. ex Willd. Against Mycobacterium smegmatis

Abstract

Tuberculosis is a worldwide prevalent and recurring disease that contributes significantly to high mortality rates. This study aimed to investigate the antioxidant, anti-mycobacterial, and antibiofilm activities of <i>Artemisia afra</i> acetone crude extract. <b>Methodology:</b> The crude acetone extract was fractionated using column chromatography and characterized by liquid chromatography-mass spectroscopy (LC-MS). A 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay was used to assess the antioxidant activity. The antimycobacterial activity against <i>Mycobacterium smegmatis</i> was screened using bioautography, broth microdilution, and growth curve assays. Molecular docking was used to predict the possible mechanisms of action of the LC-MS-identified ligands. Crystal violet was used to screen for anti-cell adherence and biofilm inhibition activities. <b>Results:</b> The crude extract scavenged 77% of the free radical at 16 μg/mL. The subfraction had a lower minimum inhibitory concentration (MIC) (0.078 mg/mL) compared to the crude extract (0.313-0.833 mg/mL). The subfraction had a concentration-dependent inhibition effect (>50%) on mycobacterial cell adherence and early biofilms. However, the mature biofilms were resistant. Two propanoate compounds, [(2S)-3-[6-acetyl-4,6-dihydroxy-3-[(1R)-1-hydroxyethyl]tetrahydropyran-2-yl]-2-hydroxy-propyl] (2R)-2-amino-3-(1H-imidazol-5-yl)propanoate and 3-(6-aminopurin-9-yl)propyl 3-(2,4-dioxo-1,3-diazaspiro[4.5]decan-3-yl) propanoate, had binding energies of -5.4 kcal/mol and -6.3 kcal/mol, respectively, against the RNA polymerase binding protein. <b>Conclusions:</b> The results show that <i>A. afra</i> acetone crude extract has antioxidant and antimycobacterial activities that can be improved by fractionation.