Influence of seasonal variation on essential oil production and phytochemical profile of <i>Zanthoxylum myriacanthum</i> cultivated under Egyptian conditions via chemometric analysis

The present study highlights the significant influence of seasonal variation on the essential oil yield and chemical composition of Zanthoxylum myriacanthum, an evergreen aromatic shrub of moderate growth. Uniform plant material (6 years old, 150 cm in height) was collected from a private garden in Giza Governorate, Egypt, during the spring, summer, and winter of 2021 and 2022. Leaves and stems were analyzed to evaluate the impact of seasonal climate on essential oil yield and composition. The results revealed that the highest essential oil yield was obtained in summer samples, followed by spring, with the lowest yields recorded in winter. The findings demonstrate that summer is the optimal season for harvesting both leaves and stems, as it results in the highest overall oil yield and elevated levels of valuable oxidized compounds such as linalool and caryophyllene. These compounds are of particular interest to the pharmaceutical and cosmetic industries due to their biological activities. Conversely, winter-harvested samples showed a higher proportion of monoterpene hydrocarbons, especially α-pinene, making this season preferable for the extraction of components used in the fragrance and perfumery sectors. Multivariate analyses (PCA and AHC) revealed three distinct seasonal clusters, confirming the impact of climatic factors, particularly temperature and light intensity, on volatile biosynthesis. These findings, representing the first chemometric analysis of this species in Egypt, provide valuable insights for optimizing harvesting strategies and enhancing its pharmaceutical, cosmetic, and fragrance applications.