Investigating seasonal variations in composition of the Rosmarinus officinalis essential oil in North Khorasan Province (Bojnord), Iran: a comparative analysis with existing literature, focusing on monoterpenol components

Rosmarinus officinalis L. (Lamiaceae), a Mediterranean aromatic plant, is valued in cosmetics, cuisine, and pharmaceuticals. This study investigates seasonal variations in essential oil (EO) composition and yield from R. officinalis harvested at Kosar University during 2023-2024. GC-MS and GC analyses revealed EO yields of 0.39-0.77%, with major compounds including α-pinene, camphene, limonene, camphor, and linalool. Seasonal shifts were observed: summer exhibited higher linalool and camphor, autumn peaked in verbenone and 3-octanone, and winter increased monoterpene alcohols (25.28%). Principal Component Analysis (PCA) distinguished three ecological groups (Group1: R3; Group2: R4, R6, R1, R2; Group3: R5), though intra-seasonal chemical differences within regions were minimal. These findings highlight the influence of seasonal dynamics on rosemary's phytochemical profile, offering insights for optimised harvest timing to enhance EO quality for industrial applications.