Diversity of the terpenoids and phenolic compounds in Majorana syriaca (Labiatae) leaves growing wild in Palestine

Essential oils, which including terpenoids, phenolic compounds, and other volatiles of Majorana syriaca leaves growing wild in Palestine were analyzed using static headspace gas chromatography mass spectrometry technique (HS-GCMS) to check for their chemical variability. The samples were collected from thirty-four individual plants naturally growing in different locations from Palestine. In such a small-restricted area, a wide range of variation in oil characteristics was observed indicating that the Palestinian region is an important center of diversity. The essential oil yield, based on air-dried weight, ranged from 10.5-mg g-1 to 54-mg g-1. The major constituents identified throughout all the harvesting periods were varied greatly among the samples examined. HS revealed major volatiles and semi-volatiles of α-phellandrene (1.62-8.13%), α-pinene (1.22-4.61%), β-myrecene (0.5-11%), m-cymene (1.86-8.61%), p-cymene (8.44-48.6%), γ-terpinene (11.96-30.8%), thymol (0.26-11.6%), and carvacrol (0.65-21.7%). As for the phenolic compounds, the results revealed that the wild growing Majorana syriaca could be characterized by the dominant presence of carvacrol. Conversely, water irrigation has showed a prominent effect on the thymol isomer production. Therefore, we suggest using isomeric distribution ratios of these isomers as a marker to distinguish wild from cultivated Majorana syriaca.