Variation of Essential Oil Content and Composition, Phenolics, and Yield Related Traits Using Different Pollination Systems in Populations of Thymus Species.

The production of self-pollinated plants could be important for improving medicinal plants secondary metabolites. In this study, 11 Thymus populations from eight species were evaluated to determine the effect of self and open pollination on agro-morphological characteristics, total phenolic content (TPC), essential oil (EO) content, and EO components. Inbreeding led to some positive effects of above mentioned traits in most of the studied populations. Total phenolic content ranged from 7.07 to 52.69 mg tannic acid equivalents (TAE) g-1 dry weight (DW) in open pollinated derived populations, while it varied from 1.2 to 55.03 mg TAE g-1 DW in self-pollinated ones. Under open and self-pollination condition, the highest EO content was obtained in T. trautvetteri (3.37 %) and T. pubescens (1.96 %), respectively. Gas chromatography-mass spectrometry (GC/MS) identified 42 compounds including thymol, carvacrol, linalool, p-cymene, γ-terpinene, terpinen-4-ol, and α-terpineol as the main compounds. In most cases, selfed plants compared to open pollinated ones, revealed higher thymol content. T. daenensis-1 showed a significant increase in thymol content (from 25.22 % to 74.3 %) due to self-pollination. Moreover, self-pollination led to emergence of some new compounds. Carvacrol methyl ether was the constituents of Thymus EO that are being reported in self-pollinated populations. Finally, inbreeding in Thymus might be suggested as a useful tool to increase genetic homogeneity for the selection of superior plants for improving secondary metabolite.

Essential oil composition, total phenolic, flavonoid contents, and antioxidant activity of Thymus species collected from different regions of Iran.

In this study, the essential oil (EO) composition, flavonoid and phenolic contents, and antioxidant activities of fourteen Thymus accessions belonging to ten species were evaluated. Gas chromatography-mass spectrometry (GC-MS) analysis revealed the presence of 38 compounds with the major constituents including thymol (12.4-79.74%), carvacrol (4.37-42.14%), geraniol (0.3-22.44%), and p-cymene (0.8-12.86%). Cluster analysis identified three groups of high thymol, geraniol/linalool, and high carvacrol. The highest phenolic and flavonoid contents were detected in T. daenensis-1 (70.6mg tannic acid equivalents (TAE) g-1 DW) and T. vulgaris (8.55mg quercetin equivalents (QE) g-1 DW), respectively. The antioxidant activities of the samples were determined using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and reducing power assay. The results demonstrated that T. daenensis-3 (IC50=273.36), T. vulgaris (IC50=289.3), and T. fedtschenkoi-3 (IC50=339.22) possessed higher antioxidant activities than the others. Finally, the Thymus species with high bioactive compounds may be recommended for further food applications.