Unveiling the Bioactive Profile of Leucas aspera Leaves: A Study on Antimicrobial and Antioxidant Activities

Abstract

Leucas aspera, a traditionally valued medicinal plant was examined for its phytochemical constituents, antibacterial activity and antioxidant potential. Qualitative screening of ethanolic, methanolic and aqueous leaf extracts revealed a broad spectrum of secondary metabolites including alkaloids, flavonoids, phenols, saponins, steroids and terpenoids demonstrating solvent dependent variability. Among the extracts, the ethanolic fraction evinced the strongest antibacterial effect against seven pathogenic bacteria, particularly Staphylococcus aureus and Escherichia coli with inhibition zones reaching 18 mm. Bioassay guided column chromatography enabled the isolation of active fractions enriched in alkaloids and phenolic compounds. FTIR and UV-Vis spectral analyses confirmed the presence of functional groups characteristic of these bioactive constituents, while GC-MS analysis identified potent alkaloids such as 2-Ethylacridine in the most active fraction. The ethanolic extract also exhibited notable hydrogen peroxide scavenging ability, achieving 63.5% inhibition at 100 µg/mL in a concentration dependent manner. Overall, the findings provide scientific validation for the ethnomedicinal use of L. aspera leaves highlighting their potential as a promising source of natural antimicrobial and antioxidant agents.