Essential oil variation in Melissa officinalis L. cultivated under industrial field conditions: effects of different harvesting times and plant materials

Abstract

Melissa officinalis L. is a cosmopolitan aromatic and medicinal plant from the Lamiaceae family, which is necessary for pharmaceutical and cosmetic production. To evaluate the impact of different harvesting times and plant materials on the essential oil content and composition of M. officinalis 4-year-old plants, the present study was conducted in Fars province, Iran, under industrial field conditions. A randomized factorial experiment with three replications was used. Each replication contained six treatments [3 harvesting of M. officinalis × 2 treatments (shade drying + fresh state)]. Hydrodistillation was used to obtain the essential oils from each treatment, which were subsequently analyzed using GC-FID and GC-MS. The results demonstrated a significant influence of harvesting times and plant materials on the essential oil content and composition of M. officinalis. The average essential oil content was 0.028% to 0.095% (w/w). At different harvest times, the fresh plant yielded a higher content of essential oil compared to the dry plant. The number of chemical constituents in the essential oils was influenced by different harvesting times and plant materials. The predominant and common constituents in all harvested plant materials were the oxygenated monoterpenes geranial (28.7-43.2%) and neral (12.9-30.9%). Based on the major compounds, the essential oils from different harvesting times and plant materials were categorized into two chemotypes: chemotype I (geranial/thymol) and chemotype II (geranial/neral). It is recommended that drying operations not be used as a post-harvest processing method to achieve the highest essential oil yield from M. officinalis.