Harvesting season dependent variation in chemical composition and biological activities of the essential oil obtained from Inula graveolens (L.) grown in Chebba (Tunisia) salt marsh

Abstract The chemical composition and the biological activities of aromatic plants may be influenced by seasonal changes. Therefore, the essential oil of Inula graveolens (IGEO), collected at Chebba salt marsh, was studied in terms of yields, compositions and biological activities, throughout four different seasons, namely spring, summer, autumn and winter (April, July, October and January, respectively). GC/MS analysis identified 30 compounds. Mostly quantitative rather than qualitative, variation was observed in the oil composition of each sample. It had been revealed a predominant presence of bornyl acetate and borneol, as well as significant differences of several compound amounts in function of the seasonal change. Biological activities were also related to the harvest season; hence, IGEO from spring gave the best antioxidant activity results and IGEO from autumn seemed to be the most potent against pathogenic microorganisms, while oils from summer and winter were the strongest inhibitors of acetylcholinesterase and tyrosinase. A matrix linking IGEO major compounds to biological was composed to identify relationships between concentrations of the volatile molecules and the biological activities of the samples. Furthermore, the seasonal variation of these main volatile constituents was also investigated through principal compound analysis (PCA). The obtained results revealed that each biological activity depends on the seasonal fluctuation of the amounts of certain chemical compounds.