Abstract
Medicinal plants are generally known as promising sources of bioactive compounds that have antimicrobial properties. Of these, phenolic compounds have gained a great deal of interest owing to their broad-spectrum activity and relatively low toxicity. Salvia indica is a plant part of the Lamiaceae family and used for herbal medicine, but little is known about whether the phenolic profile or antimicrobial activity of the plant changes as a result of freeze-drying and solvent extraction. The objective of this research was to isolate phenolic compounds from Salvia indica leaves from the Kurdistan Region, Iraq, using lyophilization and solvent extraction, and to test the antimicrobial activity against certain bacterial and fungal species. Fresh leaves of Salvia indica were freeze‐dried and ground for powder extraction, followed by Soxhlet extraction using organic solvents. The concentrated extracts were converted into powder by lyophilization. Functional groups in the phenolic-rich extract were studied through Fourier transform infrared (FTIR) spectroscopy. Antimicrobial activity was evaluated by agar-well diffusion at concentrations of 15, 30, and 60 µg against Staphylococcus aureus, Escherichia coli, and Candida albicans, with 10 independent replicates carried out and statistically analyzed. FTIR analysis revealed phenolic functional groups like hydroxyl and aromatic moieties in lyophilized Salvia indica extract. Phenolic extract had concentration-dependent antimicrobial activity against all tested microorganisms. Maximum zones of inhibition were observed at 60 µg. Escherichia coli showed marginally greater sensitivity than Staphylococcus aureus, with Candida albicans exhibiting a moderate but significant inhibitory responsiveness (p < 0.001). The results suggest that Salvia indica lyophilized phenolic extracts have potent antimicrobial effects and provide evidence that this plant is a natural source of antimicrobial agents.