Essential oil and bioactive compounds variation in myrtle (Myrtus communis L.) as affected by seasonal variation and salt stress

Vafadar Shoshtari, Z, M. Rahimmalek, M. R. Sabzalian and Hossein Hosseini. 2017. Chemistry & Biodiversity. DOI: 10.1002/cbdv.201600365.

Abstract:

An experiment was conducted to assess the effect of different NaCl concentrations (control, 2, 4 and 6 dSm^-1) and three harvesting times in different seasons including spring (9 April), summer (5 July) and fall (23 September) on essential oil yield, composition, total phenolic, flavonoid content and antioxidant activity of myrtle. Essential oil yield of dried leaves ranged from 0.2% in control and fall to 1.6 % in moderate salinity (4 dSm^-1) and spring season. The main constituents obtained from GC-MS analysis were α-pinene, 1, 8-cineole, limonene, linalool, α-terpineol and linalyl acetate in which α -pinene ranged from 11.70 % in moderate and fall to 30.99% in low salinity (2 dSm-1) and spring, while 1, 8-cineole varied from 7.42% in high salinity (6 dSm^-1) and summer to 15.45% in low salinity and spring, respectively. Salt stress also resulted in an increase in total phenolic, flavonoid content and antioxidant activity. The highest antioxidant activity based on 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity, reducing power (FTC) and β-carotene-linoleic acid model systems was found in the leaves of plants harvested in spring and summer in high stress condition. The lowest IC₅₀ values obtained in 6 dS m⁻¹ in spring (375.23 μg/ml) followed by summer (249.41 μg/ml) and fall (618.38 μg/ml). In overall, delayed harvest of myrtle in fall can lead to reduce the most of its secondary metabolites.