Chemical Fingerprinting and Antimicrobial Potential of Selected Ethnomedicinal Plants: Correlation Between Quercetin Content and Bioactivity

Due to their diverse phytochemical composition, medicinal plants belonging to the families Amaryllidaceae, Lamiaceae, and Myrtaceae possess antimicrobial and antioxidant properties. In this study, six ethanolic extracts of Allium ursinum, Allium sativum, Allium cepa, Salvia rosmarinus, Ocimum basilicum, and Syzygium aromaticum were analyzed by HS-SPME GC-MS and HPLC. Their chemical composition was evaluated and compared by chemometrics and their biological activity determined by an antimicrobial assay. A total of 72 compounds was detected (terpenoids, phenolic derivatives, fatty acids, and phytosterols). In Allium species, phytosterols were mainly abundant, whereas O. basilicum extracts were characterized by high contents of linalool and S. rosmarinus by 2-hydroxychalcone and 4-hydroxybutanoic acid lactone. Principal component analysis distinguished chemically species-specific chemical profiles, whilst the HPLC evaluation resulted in the highest quercetin content in S. rosmarinus extracts, which also displayed the best antibacterial effect against Staphylococcus aureus. Despite the observed correlation between the quercetin content and antibacterial activity, no definitive relation could be established without biological replicates, MIC evaluation, and tests with isolated compounds.