Seasonal Variation in Yield and Major Essential Oil Constituents of Wild Artemisia afra in the Eastern Coastal Belt of the Eastern Cape Province, South Africa

The variation in essential oil yield and composition of Artemisia afra across different geographical regions and harvesting seasons remains poorly understood, despite its significance for commercial and medicinal uses. This study aims to address this gap by investigating the impact of harvesting season on the yield and chemical composition of A. afra essential oil in the eastern coastal belt of the Eastern Cape, South Africa. Fresh shoot samples were collected from the Bizana, Ngqeleni, and Centane regions during summer, autumn, winter, and spring. The essential oils were extracted via steam distillation, and the chemical components were analyzed using gas chromatography-mass spectrometry (GC-MS). The highest oil yield (0.92% on a fresh mass basis) was observed in Centane, with a significantly higher concentration of 1.8-cineole (18.66%) in Ngqeleni. The content of Artemisia ketone was significantly higher in Centane (24.51%) during summer, whereas camphor peaked at 34.10% in Ngqeleni during winter. The cis - and trans -thujone isomers were most abundant in Bizana (40.37% and 10.39%, respectively). The results highlight significant variation in oil yield and composition influenced by location, season, and their interaction. These findings provide valuable insights into optimizing the production of A. afra essential oil based on geographical and seasonal factors.