Effects of Drought and Salinity on Antioxidant Mechanisms and Secondary Metabolites in Anise (Pimpinella anisum L.) Leaves

Anise (Pimpinella anisum L.) is one of the important medicinal, spices, and aromatics plants. The seedlings were grown in pots containing soil and sand (1 : 1, v/v). Some seventy-two days-old anise plants (flowering occurred) were exposed to salt (as 150 mM NaCl), while others were drought (not irrigated for 5 days). To reveal the response mechanisms, essential oil composition, phenolic, flavonoid, anthocyanin contents, as well as oxidative stress parameters and antioxidant enzyme activities in the entire aerial parts of anise, were analyzed. The antioxidant activity was determined according to radical scavenging (on DPPH and ABTS), reducing power (FRAP), and ferrous ion chelating assays. Salt and drought applications were found to increase reactive oxygen species (ROS) such as H2O2 and, and lipid peroxidation while decreased antioxidant enzyme activities such as superoxide dismutase and peroxidase. The main essential oil compound, trans-anethole, significantly increased by drought and salt. The contents of trans-anethole were recorded as 66.8, 76.2 and 72.4% in control, salt, and drought. Both salt and drought stress decreased the phenolic content, but they did not change the flavonoid contents. Anthocyanin content was significantly increased by salt while it decreased by drought. Antioxidant activity was remarkably increased by both stresses. This study revealed that anise activated the antioxidant machinery by changing not only antioxidant enzyme activities but also the composition of secondary metabolites such as essential oil, phenolic content, flavonoid, and anthocyanin to reduce the effect of salt and drought-induced oxidative stress.