Chemical Composition of the Essential Oil from Flowers, Flower Budsand Leaves of Thymus capitatus Hoffmanns. & Link from Jordan

Abstract

Composition of the essential oils hydrodistilled from the aerial parts (flowers, flower buds and leaves) of Thymus capitatus Hoffmanns. & Link (Lamiaceae) growing in Jordan was analyzed by GC and GC-MS. The plant was found rich in oil with yields of 4.3, 4.0 and 2.5 % (v/w) from the dried material of flowers, flower buds and leaves, respectively. Sixty-four components, representing >99.0 % of the oil, were successfully identified, with variable contents, in the oils obtained from the three parts. Terpenoid class composition was found to be comparable between the oils of the studied parts. Monoterpenoids represented the highest oil fraction of all the studied parts with a dominant level of oxygenated components. Leaf oil showed the highest contents of monoterpenoids (92.4 %), particularly, the oxygenated (71.3 %), while, the highest total phenolics (66.8 %) was observed in flower oil. Phenolic monoterpenoids, thymol and carvacrol, were always the principal oil components with respective levels of (31.9, 33.2 %), (30.8, 26.8 %), and (26.0,37.3 %) in flowers, flower buds and leaves, respectively. Characteristic presence of the monoterpene hydrocarbons, p-cymene (6.4–11.8 %) and γ-terpinene (3.7–10.1 %) was also observed in the oils of all parts. On the other hand, sesquiterpenoids were generally recorded in moderate-low levels in all parts; however, hydrocarbons were the main sesquiterpene components. Flower buds oil showed the highest contents of sesquiterpenoids (8.4 %), particularly the hydrocarbons (6.5 %), while, the highest level of oxygenated sesquiterpenes (2.9 %) was observed in the leaf oil. β-caryophyllene (2.5–5.2 %) and caryophyllene oxide(0.5–1.6 %) were observed as the main sesquiterpenoid hydrocarbon and oxygenated one, respectively. Interestingly, compared to other parts, leaf oil showed the highest levels of almost all the major oil components: p-cymene (11.8 %), borneol (2.7 %), carvacrol (37.3 %) and caryophyllene oxide (1.6 %), and the lowest contents of γ-terpinene (3.7 %), thymol (26.0 %), and β-caryophyllene (2.5 %).