Yield, Composition, and Chemotypes of Essential Oils from Origanum vulgare L. Aerial Parts Cultivated in Different European Countries

Origanum vulgare L. (Lamiaceae) is widely used in the food, pharmaceutical, perfumery, and cosmetic industries for the needs for which this raw material is cultivated. O. vulgare is a polymorphic species with subspecies, which differ in the structure of their reproductive organs, the location of essential oil (EO) trichomes, and the composition of EO. Therefore, it is very important to identify the most valuable chemotypes rich in biologically active substances and cultivate them more widely. This research aimed to study the chemical composition of O. vulgare EO from aerial parts (n = 17) of cultivated plants (leaves, leaves and flowers, flowering tops) from different European countries (n = 5) to determine the dynamics of EO yield and its component accumulation depending on vegetation phases, as well as to establish chemotypes of O. vulgare, which are the most promising for cultivation. EOs from the raw materials were obtained by hydrodistillation according to the European Pharmacopoeia method; their analysis was carried out by GC-MS. A total of 17 studied samples of O. vulgare aerial parts from Estonia, Turkey, Scotland, Moldova, and Italy contained 1.9-11.0 mL/kg of EO. The highest yields of EO were found in the samples from Moldova (11.0 mL/kg) and Italy (9.3 mL/kg). In total, 89 substances were identified in the studied EOs. By studying the variability of the chemical composition during the plant's vegetation period, we found the highest content of EO was noted in the phase of full flowering and at the end of blooming. Strong correlations (r = 0.61-0.84) were found between the contents of some terpenoids. The six chemotypes of O. vulgare rich in (1) caryophyllene oxide; (2) sabinene; (3) caryophyllene oxide-(E)-beta-caryophyllene; (4) (E)-beta-caryophyllene; (5) carvacrol, and (6) thymol-carvacrol were found. In terms of quantitative EO content of O. vulgare, none of the studied samples (n = 17), and in terms of total carvacrol and thymol, most of the samples (n = 15) did not meet the minimum standards of the European Pharmacopoeia. When cultivating O. vulgare for the pharmaceutical industry, it is necessary to proceed from plant propagation material rich in EO and chemotypes rich in carvacrol and thymol.