Polarity-guided fractionation of Lophira lanceolata stem bark: Differential membrane-stabilizing, protein-denaturation inhibitory and antimicrobial activities

Abstract

Lophira lanceolata is used in African traditional medicine, but the contribution of solvent polarity to the biological activity of its stem bark remains insufficiently defined. The methanol stem-bark extract was partitioned into n-hexane, ethyl acetate, n-butanol and aqueous fractions and evaluated by qualitative phytochemical tests, protein-denaturation and erythrocyte membrane-stabilization assays, agar-well diffusion, minimum inhibitory concentration determination, and acute oral toxicity testing in mice. At 1000 µg/mL, the n-hexane fraction showed 27.60% inhibition of protein denaturation, while ethyl acetate and indomethacin showed 26.60% and 27.10%, respectively. The n-butanol fraction produced 39.66% inhibition of heat-induced haemolysis, whereas n-hexane produced 25.60% inhibition of hypotonic haemolysis. These are numerical observations because inferential statistical testing was not performed. The aqueous fraction produced the largest observed antimicrobial zone (18 mm against Candida albicans at 200 mg/mL). No mortality occurred at oral doses up to 5000 mg/kg. The findings indicate polarity-dependent differences in the measured responses and support further chromatographic standardization, controlled replication and mechanism-based evaluation.