Antioxidant activity, cytotoxicity and antibacterial activity of Solanum mauritianum Scop. (Solanaceae) extracts

Abstract

• Methanol leaf and fruit extracts showed the highest TPC and TFC. • Methanol fruit extract had the lowest IC 50 in DPPH, FRAP and ABTS. • Methanol extracts were selective for Caco-2 vs HEK293. • AO/EB staining showed apoptosis like changes in Caco-2 after methanol extracts. • Antibacterial effects were moderate, MIC 240 µg/mL only against S. aureus . The limitations of conventional healthcare, coupled with rising antimicrobial resistance and oxidative stress-related pathology, necessitate the search for plant-derived target-specific agents. This study evaluated the biological activities of Solanum mauritianum Scop. (Solanaceae) leaf, stem and fruit extracts. Total phenolic content (TPC) and total flavonoid content (TFC) were quantified using Folin–Ciocalteu and aluminium chloride colourimetric assays, respectively, while antioxidant capacity was assessed using the 2,2′-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical scavenging and ferric reducing antioxidant power (FRAP) assays. In addition, cytotoxicity was evaluated in the human colorectal adenocarcinoma (Caco-2) and embryonic kidney (HEK293) cells using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, with apoptotic potential examined using acridine orange and ethidium bromide dual staining. Antibacterial activity against Staphylococcus aureus , MRSA, Escherichia coli and Pseudomonas aeruginosa was assessed by broth microdilution, with minimum inhibitory concentrations (MICs) defined at ≥ 90% inhibition. TPC and TFC followed a clear solvent- and organ-dependent pattern, with the methanol leaf extract exhibiting the highest phenolic content (73.46 ± 0.87 mg GAE/g), while methanol leaf and fruit extracts contained the highest flavonoid content (15.74 ± 0.20 and 14.04 ± 0.20 mg QE/g). Methanol extracts additionally demonstrated the strongest antioxidant potential, with fruit extracts exhibiting significantly higher activity (DPPH IC 50 10.04 ± 5.40 µg/mL, FRAP IC 50 52.50 ± 2.31 µg/mL, ABTS IC 50 92.03 ± 9.67 µg/mL). Methanol extracts further showed pronounced, selective cytotoxicity towards the Caco-2 cells (IC 50 79.12 to 114.05 µg/mL) compared to HEK293 cells (IC 50 352.18 to 495.35 µg/mL), with selectivity indices of 4.34 to 4.65 and AO/EB patterns consistent with apoptosis-like changes in Caco-2 cells. Antibacterial inhibition was concentration-dependent but generally moderate, with MICs > 240 µg/mL for most extracts, while methanol leaf and fruit extracts achieved MICs of 240 µg/mL against S. aureus . These findings indicate that polar extracts of S. mauritianum , particularly fruit and leaf, are enriched in phenolic and flavonoid constituents and exhibit strong antioxidant activity, selective cytotoxicity and limited antibacterial activity under the conditions tested, supporting their further investigation as sources of bioactive compounds.