Cultures of marine microalgae: a potential source of natural antioxidants

Abstract

Marine diatoms have garnered significant attention as a potential source of natural antioxidants including fucoxanthin (Fx). In particular, numerous studies have shown that Fx has promising applications in human health, indicating its potential in pharmaceutical and nutraceutical industries. A significant Fx production by the marine diatom Halamphora coffeaeformis, isolated from Bahía Blanca Estuary (Argentina), was evidenced in our previous studies. We also verified that cultures of this species adapted at 100 µE m-2 s-1 of light intensity showed remarkable antioxidant activity. Under this scenario, the purpose of this study was to evaluate variations in the enhancement of antioxidant activity of extracts from H. coffeaformis cultures depending on different light condition adaptation. For this, an optimized protocol for 2,2?-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt radical (ABTS?+) bleaching test was implemented. The diatom was cultured in f/2 medium at 60 μE m-2 s-1 of light intensity under a photoperiod of 12 h light:12 h dark. Fx-enriched extract was obtained by ethanolic treatment of H. coffeaformis biomass and its antioxidant activity was spectrophotometrically achieved by ABTS?+ scavenging activity measurements. The results showed an antioxidant activity of 47% for Fx-enriched extract at a concentration of 0.02 mg mL-1 and it represented half of that obtained by ascorbic acid (93%), used as a reference positive control. In addition, it was evidenced lower activity for concentrations between 0.005 and 0.04 mg mL-1 compared to our previous studies with H. coffeaeformis cultures conditioned at 100 µE m-2 s-1. In conclusion, this study demonstrates that pigment production in H. coffeaeformis can be improved by optimizing light intensity conditions and it also underscores the potential of this native species as a promising alternative source of natural antioxidants.