Comparative chemical profiling of Laurus nobilis L. leaf essential oils based on ontogenetic and locational variabilities: investigation of antioxidant and antimicrobial activities

Abstract Laurus nobilis L. (bay laurel) is among the most economically and pharmacologically significant aromatic plants cultivated in Türkiye; however, the extent to which its essential oil (EO) yield, chemical composition, and biological activities are shaped by both ontogenetic and locational factors within a single province remains poorly characterised. The present study addresses this gap by analysing 36 EO samples from six districts of Sinop province (Center, Ayancık, Erfelek, Türkeli, Dikmen, and Gerze) collected over six consecutive months (October-March 2023–2024). EOs were obtained by hydrodistillation and characterised by GC-MS/FID; antioxidant activity was assessed via DPPH radical-scavenging, and antimicrobial activity against nine microbial strains was evaluated by disk diffusion and microdilution. EO yields ranged from 0.5% to 1.5% (v/w). GC-MS analysis identified 10–22 components per sample (85.7–98.9% of total composition), with eucalyptol (43.9–65.5%), α-terpinyl acetate (7.7–15.4%), and sabinene (2.4–12.6%) as dominant constituents. Locational variation was statistically significant for six constituents including α-pinene ( p = 0.002), sabinene ( p < 0.001), and linalool ( p = 0.026). Temporal variation was limited to eucalyptol ( p < 0.001) and α-terpinyl acetate ( p = 0.017). DPPH assays yielded IC₅₀ values of 119.8–426.8 µL/mL, with the strongest activity recorded for the Türkeli-November sample (IC₅₀ = 119.8 µL/mL); neither locational nor overall temporal differences reached significance. Antimicrobial assays demonstrated broad-spectrum activity, with the lowest MIC values (320 µg/L) recorded against Bacillus spp. and Klebsiella pneumoniae ; significant locational variation was detected only for Enterococcus faecalis ( p < 0.01). Overall, geographical location proved a more consistent source of compositional variability than the ontogenetic factor, with practical implications for harvest optimisation in pharmaceutical and food applications.