Variability in essential oil composition and phenolic acid profile of Thymus daenensis Celak. populations from Iran

Abstract

Natural compounds have been widely used as food additives to replace synthetic preservatives. Essential oil (EO) and phenolic acid compounds of thyme are well known for treating a wide range of diseases. The present study was conducted to evaluate the EO yield and composition, and also phenolic acid profile for 11 populations of Thymus daenensis Celak. growing in the different areas of Iran. The EO yield (0.71–2.92 g 100 g−1 DW) was significantly different among the populations. The GC-MS identified a total of 17 components, repressing 96.1–99.7% of the total volatile oil and being mainly monoterpenes (84.2–94.3%). The main EO constitute of T. daenensis populations was thymol (63.6–83%) followed by p-cymene (0.47–7.55%), Carvacrol (1.91–4.32%), and (E)-Caryophyllene (1.37–8.5%), and 1.8-cineole (0.77–4.66%). The phenolic acid compounds determined by HPLC were rosmarinic acid (130–227 µg g-1), Caffeic acid (24.6–66.4 µg g-1), cinnamic acid (15.1–33.53 µg g−1), p-Coumaric acid (10.7–17 µg g-1), Gentisic acid (8.8–10.8 µg g−1), and chlorogenic acid (9.7–29.7 µg g−1). Principal component analysis (PCA) showed that (E)-Caryophyllene and carvacrol were the prominent compounds of Isf2 and Zan populations, respectively. The dendrogram of agglomerative hierarchical clustering (AHC) for main EO component showed four and three distinguished classes of populations according to main EO composition and phenolic acid profile, respectively, where Zan population was significantly distinguished from others. Heat map analysis showed p-cymene, 1.8-cineole, (E)-caryophyllene, and chlorogenic acid had the higher variability; however, the minimum changes occurred in thymol and gentisic acid.