The Effects of Harvesting and Different Drying Methods on the Essential Oil Composition of Lemon Balm (Melissa officinalis L.)

The herbs of Lemon balm, (Melissa officinalis L.) were dried by different drying methods of shade-drying, sun-drying and oven-drying at 40 degrees C and it compared with the fresh herb through two harvesting time. The essential oils of each treatment were obtained by hydrodistillation of the herbs, and were analysed by GC-MS. Fresh herbs had the highest essential oil content followed by shade drying, oven drying and sun drying respectively, during the first and second harvesting. The essential oil content of Melissa officinalis L. was significantly decreased towards the second harvesting. Drying methods had no effect on the number of chemical components of the essential oil, as 43 components were identified in the essential oil of each drying method. The major components were citronellal, citronellol and geranyl acetate during the first and second harvesting. Drying of Melissa of officinalis L. by sun-dried herb conditions is the most suitable for a high percentage of monoterpene hydrocarbons (during the first harvesting) or oven-dried herb. at 40 degrees C (during the second harvesting), but keeping it in fresh state are recommended for the highest oxygenated monoterpene during the first and second harvesting. On the other hand oven-dried herb at 40 degrees C is the most suitable for a high-percentage of sesquiterpene hydrocarbons and oxygenated sesquiterpene components through the first and second harvesting.