Changes in the essential oil composition, phytochemical traits and antioxidant activity of Origanum vulgare ssp. hirtum as affected by drying methods

Abstract

In this study, the effect of drying method (shade-drying, sun-drying, oven-drying at 50 °C and 60 °C, and microwave-drying at power of 560 W and 800 W) on the phytochemical composition and antioxidant activity of the Origanum vulgare subsp. hirtum was investigated. Essential oils were obtained by hydro-distillation and analyzed by GC-FID and GC-MS. The maximum essential oil (2.5%) and carvacrol (81.9%) contents were observed in drying by oven at 50 °C and microwave 560 W, respectively. Carvacrol (69.4-81.9%), γ-terpinene (6.1-13.5%), ρ-cymene (3.4-9.4%), and myrcene (0.9-2.2%) were the main components of the essential oils. The highest and lowest total phenol contents were obtained in sun-drying (92.83 mg GAE/g DW) and shade-drying (26.74 mg GAE/g DW), respectively. The highest IC50 value (149.47 μg/ml) was related to oven-drying at 60 °C, while the lowest IC50 was obtained from the plant materials dried by microwave-drying at power of 560 W (75.44 μg/ml).