Inclusive comparative study of the phytochemical composition, antioxidant potential, and antimicrobial activities of Salvia rosmarinus Spenn. essential oils from seven sites in Taza province (Morocco)

Abstract

ABSTRACT This study presents a comprehensive comparative analysis of the phytochemical composition, antioxidant properties, and antimicrobial activities of essential oils (EOs) extracted from Salvia rosmarinus Spenn. collected from seven different ecological zones (R1 to R7) in Taza province, Morocco. Leaves were harvested in late spring 2024 and hydrodistilled using a Clevenger apparatus, yielding EO percentages ranging from 1.13% (R2; Gueldaman, Pre-Middle Atlas; 34°10′25.0″ N, 3°58′06.0″ W; 776 m) to 1.67% (R1; Mghrawa site 1, Northern Middle Atlas; 33°52′55.3″ N, 4°02′58.9″ W; 936 m). The chemical profiles of the seven essential oils were determined by gas chromatography–mass spectrometry (GC-MS), revealing rich compositions predominantly composed of oxygenated monoterpenes. The principal compounds varied by location, with eucalyptol, borneol, camphor, terpinen-4-ol, and α -pinene being major constituents. The antioxidant potential of each EO was assessed through FRAP and DPPH assays. R6 ( Mghrawa site 2, Northern Middle Atlas; 33°52′10.6″ N, 4°01′47.3″ W; 1529 m ) exhibited the highest reducing power (574.1 µg AAE/mL), while R2 demonstrated the strongest radical scavenging capacity with the lowest IC₅₀ value (24.52 µg/mL), closely followed by R7 ( Mghrawa site 3, Northern Middle Atlas; 34°01′16.0″ N, 4°01′39.0″ W; 1007 m ) and R3 ( Jbarna, Pre-Rif; 34°30′22.7″ N, 3°51′30.9″ W; 744 m ) . These variations reflect differences in chemical composition, particularly in the relative abundance of active compounds. Antimicrobial assessments revealed significant bioactivity, especially against Gram-positive bacteria. Micrococcus luteus showed strong susceptibility across all samples, while Staphylococcus aureus displayed variable responses. Gram-negative strains such as Pseudomonas aeruginosa and Escherichia coli were more resistant, though Listeria innocua and Salmonella sp. exhibited notable sensitivity. Antifungal testing showed that Geotrichum candidum was more sensitive than Candida glabrata , with MIC values as low as 0.15 mg/mL in some samples. Overall, the study underscores the influence of geographical and ecological variation on the chemical profile and bioactivity of S. rosmarinus EOs. Demonstrated promising antioxidant and antimicrobial activities during preliminary in vitro evaluations. This work supports the valorization of local biodiversity and provides a basis for future investigations toward developing region-specific natural bioactive products.