In vitro evaluation of the antioxidant, antibacterial and cytotoxic activities of Osteospermum moniliferum L. leaf and stem extracts

Osteospermum moniliferum is an unexplored shrub with regard to its pharmacological properties. In this study, the antioxidant potential of O. moniliferum was evaluated using the 2,2 diphenyl-1-picrylhydrazyl (DPPH) and ferric-reducing antioxidant power (FRAP) assays. The DPPH assay indicated that the stem methanolic extract demonstrated the most pronounced scavenging capability (83.16%) at the minimal concentration of 15 mg/mL, with IC50 values recorded at 5.08 mg/mL. The IC50 values obtained from the FRAP assay were suboptimal for the leaf extracts (>1000 µg/mL), whereas the stem extracts exhibited remarkable activity, with values of 2.75 mg/mL for methanol, 3.52 mg/mL for chloroform, and 4.49 mg/mL for hexane extracts. The cytotoxicity was evaluated against three human cell lines, viz. breast adenocarcinoma (MCF-7), embryonic kidney (HEK293) and lung carcinoma (A549), using the (MTT) assay. Moderate activity was observed for the leaf (44.66±0.09 µg/µL) and stem (47.37±0.08 µg/µL) hexane extracts for the HEK293 cell line. In contrast, stem methanol, leaf methanol, leaf chloroform and stem chloroform extracts had low cytotoxic activity against the MCF-7 cell line. All extracts exhibited promising antibacterial activity against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. These findings could potentially contribute to the advancement of naturally derived compounds used in healthcare.

Key words
Antioxidant; cytotoxicity; antibacterial; Osteospemum moniliferum; Asteraceae