Isolation and identification of a novel antioxidant isolated from marine algae and its antioxidative effect

Abstract

Seaweeds or their extracts have also been studied as potential natural antioxidant in recent years. Although most photosynthesizing plants including seaweeds are exposed to a combination of light and high oxygen concentrations, which lead to the formation of free radicals and other strong oxidizing agents, they seldom suffer from any serious photodynamic damage in vivo. The observations suggest that their cells have protective antioxidative mechanisms as well as antioxidative compounds. Therefore, it is important to extract or isolate useful bioactive compounds from seaweeds.A potent free radical scavenging activity was detected in the diethyl ether fraction, and the active compound was isolated via silca column chromatography followed by RP-HPLC. Finally, the novel antioxidant was identified on the basis of LC-MS and NMR spectroscopic data as phloroglucinol-6,6-bieckol, a kind of phlorotannin. The antioxidant activities of phloroglucinol-6,6-bieckol were evaluated by several in vitro assays such as radical scavenging activities (DPPH, alkyl, hydroxyl, superoxide radical scavenging assays) using electron spin resonance (ESR) spectrometry, intracellular reactive oxygen species (ROS) scavenging activity, and DNA damage assays.In this study, we screened radical scavenging activity from 21 species of marine algae, and Ecklonia cava was selected for further study due to its profound radical scavenging activity. The active compound was identified as a type of phlorotannin, phloroglucinol-6,6-bieckol, which evidenced prominent radical scavenging activity and also exerted a protective effect against H2O2-induced cell damage. Thus, phloroglucinol-6,6-bieckol may prove useful in the food and pharmaceutical industries, owing to its marked oxidative stress-inhibitory effects.