Phytochemical analysis , in vitro evaluation of antioxidant and antimicrobial activities of phenolic extracts from Posidonia oceanica ( L . ) Delile leaves

Posidonia oceanica is one of the few marine higher plants endemic to the Mediterranean Sea, considered as an indicator of environment quality in coastal areas. Total phenolic, flavonoid and tannin contents were determined in FP (soluble free phenolic) and BP (insoluble-bound phenolic) extracts obtained from Posidonia oceanica intermediate leaves. Higher phenolic content was ob tained in FP (27.71± 2.4 GAE/g DW), but higher flav onoid content and tannin contents were detected in BP (19 .16± 1.8 mg QE/g DW, and 3.34± 0.5 mg CE/g DW, respectively). Identification and quantification of phenolic compounds were carried out using RP-HPLC analysis. Protocatechuic, ferulic acids and catechin were the major compounds (constituting 90%) of the identifi ed compounds in FP extract, while in BP extract, querc etin was the main flavonol aglycone (about 95%). Hi gher DPPH scavenging activity (IC 50, 2.5 mg/ml), was measured for BP extract. The stud y of the antimicrobial activity of FP extract showed that it exhibited potentiating ac tivity of some antibiotics. These findings suggeste d that Posidonia oceanica could be considered as a natural source fo r pharmacological products.