Maximising phenolic compounds and antioxidant capacity from Laurencia intermedia using ultrasound-assisted extraction

Abstract

Laurencia intermedia, which belongs to red algae (Rhodophyta), has been found in tropical shore areas. Recently, it has been reported to be a rich source of bioactive compounds; however, there have been limited studies on extraction techniques for recovering bioactive compounds from L. intermedia. Hence, this study was conducted to optimise the ultrasound extraction conditions for maximising recovery yield of total phenolic content (TPC) and antioxidants from L. intermedia using response surface methodology. The results showed that the ratio of sample to solvent had the strongest effect on TPC, while extraction temperature, extraction time, ethanol concentration and ratio of sample to solvent had significant influence on antioxidant power. The yield of TPC, DPPH scavenging ability and ferric reducing antioxidant power were 161.79 ± 3.52 mg GAE/100 g, 32.30 ± 1.20 mg TE/100 g and 87.77 ± 3.17 mg TE/100 g, respectively at the optimum extraction conditions (50 °C, 60 min, 30% ethanol and sample to solvent ratio of 2 g/100 mL). These conditions were employed to prepare L. intermedia extract for subsequent fractionation step, which generated n-hexane, ethyl acetate and aqueous fractions. Among these fractions, ethyl acetate fraction was found to possess the highest yield of TPC and the greatest antioxidant capacity that could be used for further isolation and purification of individual compounds.