Effect of Harvesting Time Variations on Essential Oil Yield and Composition of Sage (Salvia officinalis)

The objective of this study was to evaluate the production, contents, and essential oil (EO) components of sage as a function of the diurnal variation. The EOs from the aerial parts of the plant harvested at different day/night times were extracted by hydro-distillation. Plants were harvested in 2 h intervals (twelve harvesting times during each 24-h day). Harvesting between 4:00 and 6:00 p.m. revealed the highest EO percentage (1.14%), whereas harvesting between 04:00 and 06:00 a.m. indicated the minimum EO percentage (0.599%). The analysis of the EO identified 32 components. The major identified EO compounds were cis-thujone (34.38–46.18%), 1,8-cineol (8.70–11.07%), camphor (9.65–14.38%), and trans-thujone (9.43–14.19%). The highest value of cis-thujone (46.18%) was related to the harvest time of 04:00–06:00 a.m., and the lowest value (34.38%) was recorded at the harvest time of 00:00–02:00 a.m. The highest value of trans-thujone (14.19%) was obtained between 10:00–00:00 p.m., and the lowest value (9.43%) was obtained between 10:00–12:00 a.m. Camphor was another dominant compound where the highest (14.38%) was observed at 00:00–2:00 a.m. Our findings in sage, for the first time, may pave the route towards the optimization of sage EO quality and quantity by selecting the best harvesting time of the plants.