Posidonia oceanica (L.) Delile: antioxidant activity and nutraceutical content

Introduction: Posidonia oceanica (L.) Delile (P. oceanica) is an endemic aquatic plant of the Mediterranean Sea, incorrectly known as an alga. It builds thick meadows, from 1 to 40 meters deep and green leaves, which may reach 1 meter in height. It is an important habitat for fisheries and play role in monitoring of pollutants herbicides, pesticides and other chemical contaminants. The plant has been used since ancient times and some uses in traditional medicine were confirmed as well as antibacterial and antifungal. In the search for a sustainable livestock system that balances natural resources and economic benefits, considerable efforts have been made to find new sources such as marine plants. The aim of this study is to evaluate the antioxidant capacity and nutraceutical content expressed as total polyphenols, rutin, quercetin in leaves extracts of P. oceanica. Materials and methods: Several samples of leaves of P. oceanica has been harvested in sea of Sicily (Egadi Islands Marine Protected Area) in three different period of years (April, July and September). The leaves were exsiccated at 30°C for 14 days and successively extracted with 15% aqueous ethyl alcohol (10g in 100ml) at 25°C for 72 hours. The ethyl alcohol was removed under vacuum. The extracts were investigated for the antioxidant activity by DPPH free radical scavenging and FRAP test assays. The levels of flavonoids (quercetin and rutin) were measured by HPLC method. The total polyphenols contents of the extracts was estimated with spectrophotometric method. Results: The results obtained demonstrated that extracts of P. oceanica harvested in September showed an higher DPPH inhibition (IC50 0.23 0.012 mg/ml) compared to the plant harvested at April or July (P<0.001 and P<0.01 respectively). Similarly the samples harvested in September showed high antioxidant power, evaluated by FRAP test (1.3070.057 mmol Fe2+ equivalent per gram), significantly different versus the leaves harvested in April (P<0.05). In addition all extracts showed high levels of polyphenols (20.21±0.899 mg/ml in April; 84.50±3.009 mg/ml in July and 94.15±1.190 mg/ml in September). The quercetin concentration in samples was low (0.21±0.015 μg/ml in April; 0.22±0.009 μg/ml in July and 0.23±0.005 μg/ml in September) and not significant difference were observed in the different time of harvested, otherwise the rutin was higher (2.53±0.758 μg/ml in April; 6.54±0.958 μg/ml in July and 6.97±1.64μg/ml in September) with a significant increase in July and September (p< 0.01). Discussion: In this study we evaluated the nutraceutical content and the antioxidant activity of P. oceanica leaves extracts. The antioxidant activity of plants is mainly contributed by the active compounds as polyphenols and flavonoids quercetin and rutin when ethanol 15% is used as solvent. The leaves of P. oceanica resulting in a peculiar phytocomplex endowed with interesting biological properties. The study shows that there are differences in the contents of nutraceutical based on different harvesting time. Conclusion: The results obtained suggested that P. oceanica may be used for many industrial products and thanks to its nutraceutical content and its antioxidant activity it could represent a sustainable and low-cost perspective in the field of animal nutrition.