In vitro evaluation of antioxidant activities of free and bound phenolic compounds from Posidonia oceanica (I.) Delile leaves

The contents of phenolics, flavonoids and proanthocyanidins were determined in FPC and BPC extracted from Posidonia oceanica leaves. High phenolic content was obtained in both FPC and BPC (328.00 and 407 mg/g, respectively). Flavonoids were mainly detected in BPC (94.4 mg quercetin equivalent/g). However, the amount of flavonoids in FPC was 2 times lower. The amount of proanthocyanidins was slightly higher in FPC than in BPC (93 versus 73 mg catechin equivalent/g). The highest DPPH and O-2(-) scavenging activities (IC50 = 10.71 mu g/ml and 27.93 mu g/ml, respectively) and highest reducing power (IC50 = 9.4 mu g/ml) were found in BPC. Inhibition of lipid peroxidation was detected in FPC, as measured by the ferric thiocyanate (IC50 = 2.08 mu g/ml) and the beta-carotene-linoleic acid (IC50 = 33.33 mu g/ml) assays. Noteworthy, we observed low Fe++-chelation and OH-scavenging activity in both FPC and BPC extracts. These findings indicated that, P. oceanica leaves could be used as a natural preservative ingredient in food and/or added to fish and marine products to prevent lipid peroxidation.