Variations in Essential Oil Composition and Chemotype Patterns of Wild Thyme (Thymus) Species in the Natural Habitats of Hungary

Abstract

A comprehensive study was conducted on the diversity and characteristics of five Thymus species native to Hungary, concerning frequency of occurrence, habitat preferences, essential oil content of the dried flowering shoots, and chemotype patterns determined by GC/MS. Our main aims were to provide an overview of the essential oil diversity of thyme resources and select the best genotypes with potential for cultivation and utilization. Based on the results obtained in 74 populations of 63 localities belonging to 15 regions of the Transdanubian and Northern Hungarian Mountains, considerable essential oil diversity was found. Thymus pannonicus (TPA), of generalist character, was proven to be the most frequent species (38 populations), while T. serpyllum (TSE) occurred only in two habitats. High average amounts of essential oil (EO) were shown for T. pannonicus (0.46 mL/100 g DW), T. pulegioides (TPU: 0.47 mL/100 g DW), and T. serpyllum (0.59 mL/100 g DW), while low EO accumulating ability was detected in T. glabrescens (TGL: 0.26 mL/100 g DW) and in T. praecox (TPR: 0.10 mL/100 g DW). In general, the thymol chemotype was the most frequent (34 populations), found together with the related molecules (p-cymene: 26; γ-terpinene: 15), while numerous other monoterpenes (M: geraniol: 12, linalool: 7) or sesquiterpenes (S: germacrene D: 25, β-caryophyllene: 21) were dominant, as well as combined (MS) chemotypes, which were also described in the Eos of Thymus species in Hungary. Our findings confirmed that T. pannonicus shows potential for cultivation with homogenous drug quality, adequate amounts of essential oil, and stability in EO composition. Data from original habitats also supports its high tolerance and adaptability to diverse environmental conditions, which is advantageous when facing climate change and extremities.