The impact of both the season of collection and drying on the volatile constituents of Origanum vulgare L. ssp. hirtum grown wild in Croatia

Samples of Origanum vulgare ssp. hirtum were collected from the same geographic area in the south of Croatia at different seasons of growth. The maximum fluctuations found for the main components from fresh plant material were: thymol [149.2–1124.4 mg (100 g)–1], carvacrol [51.6–564.3 mg (100 g)–1], p-cymene [20.2–220.9 mg (100 g)–1] and γ-terpinene [50.1–217.5 mg (100 g)–1]. The oregano that was analysed belonged to a thymol/carvacrol chemotype. The season of collecting affected the qualitative and quantitative composition of the essential oil. The most impressive difference was the increase of p-cymene content in August. After the drying of the plant material, all samples showed a minor decrease in essential oil yields when compared with fresh plants. Drying, at room temperature, had no effect on the qualitative composition of oregano oil. Because of the variability of essential oil compositions from seasonally collected fresh and dried oregano, it would be important to check the quantity and quality of such components before usage.