On the effect of initial drying techniques on essential oil composition, phenolic compound and antioxidant properties of anise (Pimpinella anisum L.) seeds

The effect of drying methods (sun, oven and shade drying) on aniseeds was investigated in terms of their essential oils, phenolics and antioxidant activities. The optimum yield of essential oil was found in shade drying (2.62%). Fourteen volatile compounds were determined in all samples with variation of the main component proportions depending on drying methods. Thus, trans-anethole (84.21%) and estragole (3.82%) proportions significantly increased in shade drying. The highest total phenol and flavonoid contents of aniseeds were recorded in shade drying (42.70 mg of GAE/g and 53.55 mg of QE/g, respectively) while the lowest contents in oven drying at 60 °C (31.15 mg of GAE/g and 46.20 mg of QE/g, respectively). In all drying methods, naringin (41.04–43.76%), chloroginic acid (23.13–27.19%) and rosmarinic acid (12.26–15.95%) were the predominant phenol compounds. Although shade drying increased the antioxidant activity, aniseed extracts exhibited higher radical scavenging (IC50 = 10.15 µg/mL), reducing power (EC50 = 187.24 µg/mL) and chelating (IC50 = 6.85 mg/mL) capacities than essential oils (IC50 = 114.87 µg/mL, EC50 = 548.05 µg/mL and IC50 = 58.65 mg/mL, respectively). In conclusion, Shade drying method was found to enhance essential oils, phenols and antioxidant activities in aniseeds.