Seasonal Variation of Essential Oil Quantity and Quality in Bay Laurel (Laurus nobilis L.) Leaves from Montenegro

Seasonal variation is recognized as a key factor affecting the essential oil (EO) yield, chemical composition, and antioxidant activity of <i>Laurus nobilis</i> L. from the Montenegro coast, which constituted the focus of this research. The bay essential oil (BEO) yield was higher in summer (2.12%) and autumn (2.03%) than in winter (1.26%) and spring (1.28%). The total number of BEO components, depending on seasonal variability, ranges from 31 (summer) to 34 (winter and spring). 1,8-cineole (eucalyptol) was the major aromatic compound in all seasons, with the highest content recorded in summer (52.4%). Linalool, as the second most abundant component, is present in the autumn harvest (14.1%), while α-terpinyl acetate, as the third most abundant component, is most prevalent in the winter-spring period (9.6-9.7%). Two groups of monoterpenes, namely the oxygen-containing monoterpene derivatives (80.1%), constitute the most abundant components in BEO leaves, as well as monoterpene hydrocarbons (14.3-15.5%). The phenylpropanoids were the least abundant (4.9-6.3%). Stronger antioxidant activity (DPPH) during an incubation time of 20 min was shown by the BEOs isolated from autumn (EC50 value of 1.15 mg/mL). Early autumn (September) represents the optimal harvest time for <i>L. nobilis</i> in Montenegro, as they ensure a high essential oil yield and better quality, reflected in a high 1,8-cineole content and stronger antioxidant activity of the oil. These results demonstrate that seasonal variations are key factors regulating the quantity and quality of BEO, providing important information for optimizing harvest strategies for medicinal and industrial purposes.