Antioxidant activity of extracts from marine macroalgae, wild-collected and cultivated, in an integrated multi-trophic aquaculture system

Methanolic and hydroethanolic extracts of ten common species of marine macroalgae (5 Rhodophyta, 2 Ochrophyta and 3 Chlorophyta) of the intertidal system of the Canary Islands were screened to evaluate their in vitro antioxidant activity by DPPH radical scavenging activity and reducing power. The concentration of bioactives as pigments and phenolic compounds was also determined. Wild-collected algae and these cultivated in an integrated multitrophic aquaculture (IMTA) system during one month, were analyzed. The highest antioxidant activity was observed in Halopithys incurva, Fucus spiralis and Treptacantha abies-marina. The hydroethanolic extracts exhibited higher reducing power than methanolic extracts in most species. However, the differences in DPPH scavenging activity between solvents were not so high, and only the hydroethanolic extracts of some species showed antioxidant activity. The highest concentration of polyphenols was reached in H. incurva, T. abies-marina and F. spiralis. However, compared to collected seaweeds, the percentage of these compounds was lower in cultivated samples. The highest concentrations of chlorophyll a and carotenoids were found in T. abies-marina, Codium intertextum and F. spiralis. In red algae, the phycoerythrin (PE) content was higher in H. incurva, followed by P. capillacea. After culture, pigment content increased in most species, depending on the assimilation capacity of the ammonium from fishpond effluents. C/N ratio in samples collected in the field was high, indicating nitrogen limitation. After cultivation under high nitrogen availability (fishpond effluents), the ratio decreased in all species, especially in C. intertextum, F. spiralis and H. incurva, by the accumaltion of N-compounds. Pearson coefficient only showed significant correlations between the reducing power and some bioactive compounds, particularly polyphenols and PE. In conclusion, culture under IMTA conditions changed the biochemical composition of algae. The antioxidant activity did not decrease after culture in several species, despite the reduction of phenolic compounds, probably due to the benefits of the high N availability in the IMTA.