Bioassay-guided isolation of antioxidant constituents from the methanol extract of Artemisia oliveriana Bunge

Abstract

Today, medicinal plants have been attracted by many researchers in order to discover natural biologically active compounds. Artemisia oliveriana bunge is a native Iranian plant growing mainly in the east of Isfahan province. Ethnopharmacological, medicinal and phytochemical studies have revealed the antimalarial, antimicrobial and anticancer activities of the plant. Purpose of this study was the bioassay-guided isolation and identification of antioxidant compounds from the methanol extract of the plant [1]. So, methanol extract of the plant was divided into two aqueous and hexane fractions by a liquid-liqiud extraction. For obtaining phytochemical profile of the aqueous fraction, it was subjected to an analytical high-performance liquid chromatograph (Analytical HPLC). After optimization and scaling up the elution method, a preparative HPLC was applied to fractionate the extract to 12 sub-fractions (F 1 -F 12 ). The antioxidant effect of sub-fractions was measured by a DPPH free radical scavenging assay. Fraction F 4 showed the highest antioxidant property by an inhibition of 85.85% of DPPH free radicals at a concentration of 100 µg/mL. For isolation and purification of effective compounds of this active fraction, it was subjected to another preparative HPLC system following by antioxidant tests on purified compounds. This attempt led to the isolation of a structurally new coumarolignane (F 9' ) skeleton. It revealed a high antioxidant activity with 80.93% inhibition of free radicals at the same concentration. 1D and 2D nuclear magnetic resonance (NMR) technique including ( 1 HNMR, 13 CNMR, COSY, HMQC and HMBC) were used to elucidate the structure.