Preparation and antioxidant property of extract and semipurified fractions of Caulerpa racemosa

Abstract

A microwave-assisted extraction method has been developed for the extraction of phenolic compounds from the green alga, Caulerpa racemosa. An L18(3)5 orthogonal experimental array was designed to optimize the extraction conditions. Total phenolic content was determined by Folin–Ciocalteu method. Under the optimized conditions (microwave power, 200 W; ethanol concentration, 60%; extraction time, 40 min; extraction temperature, 50°C; solvent-to-material ratio, 40 mL g−1), the maximum total phenolic content reached 67.89 ± 3.88 mg 100 g−1 dried sample. The crude ethanolic extract was further purified by liquid–liquid partition to afford two fractions, of which the ethyl acetate-soluble fraction (EAF) exhibited the strongest antioxidant activity in the hydroxyl and 2,2-diphenyl-1-picrylhydrazyl radical scavenging assays and reducing power. EAF was further divided into four subfractions, designated as EAF1 to EAF4, by silica gel vacuum liquid chromatography. The antioxidant capacity of the subfractions was in the following order: EAF1>EAF2>EAF4>EAF3. The results of IR spectral and HPLC analysis, including the research on the correlation between antioxidant capacity and total phenolic content, suggested that phenolic compounds of medium polarity were the major contributors to the antioxidative activity of C. racemosa. The present findings might contribute to a rational basis for the use of phenolic-rich fractions and subfractions as natural antioxidants in different food/pharmaceutical products.