Comparative Phytochemical Characterization and Bioactivity Profiling of Serbian Ajuga Species from Different Localities: Antioxidant, Antityrosinase, Antimicrobial and Anti-Pyocyanin Activities

Herbaceous and subshrub species of the genus Ajuga are recognized as valuable sources of bioactive metabolites with diverse pharmacological properties. This study comparatively evaluated the phytochemical composition and the in vitro biological activities of Ajuga chamaepitys, A. genevensis, A. laxmannii, and A. reptans collected from different localities in Serbia. UHPLC-MS/MS profiling identified p-hydroxybenzoic acid and ferulic acid as the predominant phenolic compounds. A. reptans exhibited the highest total phenolic content (120.52 mg GAE/g dw), along with the strongest antioxidant activity in DPPH, ABTS, β-carotene bleaching, and FRAP assays, as well as the highest antibacterial activity. A. laxmannii contained the highest flavonoid content (48.95 mg QuE/g dw) and showed the strongest antifungal activity, whereas A. genevensis demonstrated the most potent tyrosinase inhibitory activity. Notably, A. genevensis extracts exhibited pronounced anti-pyocyanin activity, approximately twofold stronger than ampicillin. These findings demonstrate significant species- and locality-dependent variation in the phytochemical composition and biological activity and identify Serbian Ajuga species as promising natural sources of antioxidant, antimicrobial, and antivirulence compounds with potential pharmaceutical and food applications.