Essential oil composition and isolation of free-radical-scavenging phenolic glycosides from the aerial parts of Ajuga chamaepitys growing in Iran

Abstract

From the methanolic extract of the aerial parts of Ajuga chamaepitys (L.) Schreb., Lamiaceae, one of the Iranian medicinal plants, the phenylethanoid glycoside, acteoside, and two flavone glycosides, chrysoeriol 7-O-glucopyranoside (3'-methoxy-luteolin 7-O-glucopyranoside) and apigenin 7-O-rhamnopyranoside, were isolated by a combination of solid-phase extraction (SPE) and preparative reversed-phase high-performance liquid chromatography (prep-RP-HPLC) methods. Structures of the isolated compounds were elucidated by spectroscopic means. The free-radical-scavenging properties of the extracts, fractions and isolated compounds were determined by the 2,2-diphenyl-1-picryl-hydrazyl (DPPH) assay. While among the extracts, the MeOH extract showed the highest level of free-radical-scavenging activity (RC50 1.15 x 10(-1) mg/mL), chrysoeriol 7-O-glucopyranoside was the most active (RC50 3.00 x 10(-3) mg/mL) among the isolated compounds. The GC-MS and the GC-FID analyses revealed a-pinene (23.66%), beta-pinene (9.33%), 1-octen-3-ol (9.72%), beta-phellandrene (8.70%) and germacrene-D (7.92%) as the major components of the essential oils derived from the aerial parts of this plant. The presence of phenolic glycosides and the alpha- and beta-pinene-rich essential oils in A. chamaepitys may provide some rationale for the traditional medicinal uses of this species in Iran.