Abstract
In this study, the composition of the essential oil, flavonoid and phenolic contents, and the antioxidant activities of three Phlomis species from Jordan (P. viscosa Poiret., P. platystegia Post. and P. brachyodon Boiss.) were examined. The essential oil from fresh and air dried aerial parts of these Phlomis species was obtained by hydrodistillation and analyzed by GC-MS. Germacrene B, E-caryophyllene and γ-muuroleneas were the major constituents of the oil from P. viscosa, while viridiflorol, β-eudesmol, Linalool and γ-cadieneneas dominated in P. platystegia, and γ-muurolene, α-humulene, γ-himachalene and Linalool were the chief components of the oil from P. brachyodon. Comparatively, the different oils extracted from the air-dried parts of the three Phlomis species showed less content in monoterpene and sesquiterpene hydrocarbons and higher amounts of oxygenated monoterpenes and sesquiterpenes than the oils from the same fresh areal parts. The total phenol and flavonoid contents from crude fractions obtained from these three species were determined by using Folin-Ciocalteu and AlCl
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assays. And four biochemical assays, namely 1, 1-Diphenyl-2-picrylhydrazyl (|DPPH), 2,22 -azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS), hydrogen peroxide scavenging (hydroxyl) and ferrous ion chelating (FIC) were used to evaluate antioxidant activities. The butanol fractions from the different species showed the highest content of both total phenol and flavonoid, when compared to aqueous and methanol extracts. Similarly, the butanol fraction showed the highest antioxidant capacity among the other extracts, as revealed by DPPH free radical scavenging activity, ABTS free radical scavenging assay, Hydroxyl radical assay and ferrous ion chelating assays.