Effect of Different Drying Methods and Distillation Times on Essential Oil Composition and Antioxidant Content of Rosemary

The aim of this study is to determine the effect of different drying methods and distillation times on the antioxidant and essential oil contents of rosemary. The essential oil content of rosemary extracts was determined using hydrodistillation and its composition by GC-FID/MS. The antioxidant content of deoiled materials was quantified on the LC-MS/MS. Carnosol and carnosic acid contents (LC/MS-MS) and essential oil compositions (GC-MS) were determined after each treatment. The highest essential oil (2.34%), carnosol (0.62%), and carnosic acid (0.85%) contents of dried samples were determined at 45C. Some variations were also observed in the essential oil composition of dried samples. These quality parameters showed significant variations over different distillation times. And, the distillation time of 120 min was determined more appropriate to obtain essential oils and antioxidant compounds at a high yield. To produce rosemary extracts with a high content of essential oils and antioxidant compounds, it is highly recommended that the fresh plants should be first dried at 45C, and then dried samples should be processed into essential oils by hydrodistillation for 120 min. The remnants of plant materials from the production of rosemary essential oil could be used to produce carnosol and carnosic acid. Eventually, essential oils and antioxidant compounds should be extracted from rosemary in an integrated manner.