The effect of salinity on Fucus ceranoides (Ochrophyta, Phaeophyceae) in the Mondego River (Portugal)

摘要

Algae (and their extracts) are increasingly important for pharmaceutical applications due to the diversity of useful compounds they contain. The genus Fucus contains one of the most studied species, Fucus vesiculosus. The species F. ceranoides differs from the others of the genus by presenting longitudinal air-vesicles and a capacity to survive at low salinities. It is an alga that inhabits the Mondego River estuary (Portugal), at the southern limit of its distribution, and can serve as a role model to understand the effect of a salt gradient on the production of bioactive compounds. We assessed the phenolic content and antioxidant activity of different F. ceranoides extracts (e.g. methanolic, aqueous and polysaccharide) prepared from samples harvested from two different zones to evaluate if the adaptation of F. ceranoides to different salinity levels influenced its chemical composition. The antioxidant activity of the extracts was determined using 1,2-diphenyl-picrylhydrazyl (DPPH) and 2.2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals. These assays demonstrated that the methanolic extract of lyophilized F. ceranoides that grew at low salinities was the most bioactive, i.e. DPPH (IC50=50.39 μg/mL) andABTS (TEAC=2.42). The total phenolic content (Folin-Ciocalteu method) and the methanolic extract of the lyophilized F. ceranoides collected from a low salinity habitat exhibited the highest phenolic content (PGE=49.48 μg/mg of lyophilized extract) amongst those sampled. Thin layer chromatography (TLC) and Fourier transform infrared spectroscopy (FTIR) were used for the identification of compounds in the extracts. This characterization allowed confirmation that the various extracts contained almost the same compounds but with notable quantitative differences. Based on these results, we conclude that there were differences in the quantity of the compounds due to the effect of salinity. The drying methods used were also found to have influenced the quality of the extracted compounds.