In vitro evaluation of the antibacterial, antioxidant, and phytochemical investigation of Clematis simensis Fresen and Warburgia ugandensis Sprague in Ochollo, South Ethiopia

Antimicrobial resistance (AMR) represents a critical global health crisis, threatening the efficacy of conventional antibiotics and challenging modern healthcare systems. In light of declining synthetic drug discovery, medicinal plants are gaining renewed attention as sustainable sources of novel bioactive compounds with antimicrobial and antioxidant potential. This study evaluated the phytochemical profile, antibacterial, and antioxidant activities of Clematis simensis (C. simensis) Fresen and Warburgia ugandensis (W. ugandensis) Sprague, two ethnomedicinal plants traditionally used in southern Ethiopia. A laboratory-based experimental study was conducted at Arba Minch University, Microbiology and Parasitology Laboratory, between March and August 2020. Fresh leaves of both plants were collected from Ochollo, Arba Minch Zuria Woreda. Qualitative and quantitative phytochemical analyses were performed, followed by antibacterial and antioxidant assays. The bioactive compounds in the methanolic extract of the most active plant, W. ugandensis, were further characterized using Fourier-transform infrared spectroscopy (FTIR) and gas chromatography–mass spectrometry (GC–MS). Methanol extracts yielded higher crude extract percentages (18.4% for C. simensis) than petroleum ether extracts. Phytochemical screening revealed the presence of phenols, flavonoids, saponins, tannins, steroids, and terpenoids in both species, with methanol as the optimal solvent. The methanol extract of W. ugandensis exhibited the highest antibacterial activity, producing a 26.33 ± 0.44 mm inhibition zone against Staphylococcus aureus (S. aureus), followed by C. simensis (21.83 ± 0.44 mm against Pseudomonas aeruginosa (P. aeruginosa). The petroleum ether extract of W. ugandensis showed the lowest activity (11.0 ± 0.58 mm against Listeria monocytogenes (L. monocytogenes). Methanol extracts showed strong antioxidant activity in the DPPH assay, with the lowest IC₅₀ for W. ugandensis (118.22 µg/mL), whereas petroleum ether extracts exhibited weaker activity (highest IC₅₀: 476.93 µg/mL). FTIR analysis identified functional groups such as aliphatic C–H, carbonyl (C = O), alkoxy (C–O), and C = C bonds. GC–MS analysis of W. ugandensis revealed key metabolites including squalene, hexadecanoic acid methyl ester, methyl 9, 10-octadecadienoate, methyl 12, 13-tetradecadienoate, and 1-isothiocyanato-3-methyladamantane. The findings confirm that C. simensis and W. ugandensis possess a measurable antimicrobial and antioxidant activities, attributed to their diverse phytochemicals. These species may serve as potential sources of bioactive compounds and warrant further investigation through detailed mechanistic and in vivo studies.