Diurnal, and seasonal dynamics in essential oil content and composition of cultivated Helichrysum italicum (Roth) G. Don

Helichrysum italicum from the Asteraceae family is a small odorous shrub that is distributed in the Mediterranean region different altitudes. However, the species was not naturally found in the flora of Türkiye. Cultivation interest in H. italicum has grownsince its cosmetic and pharmaceutical usage. In the present study, H. italicum plants (seedlings were obtained from the same source) were cultivated in Hatay (Mediterranean, 149 m altitude) and Uşak (Continental, 906 m altitude) cities of Türkiye. Harvestings were done in the spring and autumn, at three different hours of the day (09.⁰⁰, 13.^00, and 18.⁰⁰) in both locations. Soil samples were analyzed to determine some soil properties in both locations. Harvested aerial plant samples were evaluated for essential oil content and composition with three replicates. The experimental field soils' pH values were similar, however there were differences in the ratio of soil lime and macro-microelements. The essential oil content varied between 0.29 and 0.59% in all examined variables. Generally, neryl acetate and α-pinene were found as a main component in all essential oils. Neryl acetate contents ranged between 8.07 and 36.66%, while α-pinene content was found between 13.93 and 31.18%. In the spring harvest, harvesting in the evening produced higher neryl acetate in the continental environment, whereas harvesting at any time of day did not affect the amount of neryl acetate in the Mediterranean climate. In the autumn harvest in the Mediterranean environment, the neryl acetate content was higher in the morning harvest, while neryl acetate content in autumn was comparatively low in the continental climate. Examining the seasons has shown that, in a Mediterranean environment, harvest time is not very significant, but in a continental climate, spring harvest could be favored.