Screening microalgae as potential sources of antioxidants

Abstract

Microalgae can stimulate antioxidant defense systems as adaptive responses to oxidative stress. Therefore, these organisms can be a potential source of natural antioxidants. In this work, forty-two strains of microalgae and cyanobacteria were selected within major groups held in the Coimbra Collection of Algae (ACOI). The antioxidant capacity of ethanolic extracts was determined by two spectrophotometric methods: the 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) assay and the 2,2-di(4-tert-octylphenyl)-1-picrylhydrazyl (DPPH) assay. Raspberry extract was used as a reference for comparison purposes. The ABTS assay showed an antioxidant capacity range of 16.61 ± 0.15 to 258.20 ± 0.65 mg Trolox (TE) (100 g)−1 fresh biomass (FW). High antioxidant capacity was observed in Eustigmatophyceae and Chlorophyta, with high results achieved for Vischeria helvetica ACOI 299, Characiopsis aquilonaris ACOI 2424, and Micrasterias radiosa var. elegantior ACOI 1568. The DPPH assay revealed that the eustigmatophytes Characiopsis sp. ACOI 2428, Characiopsis minima ACOI 2426, and V. helvetica ACOI 299, the cryptophyte Cryptomonas pyrenoidifera ACOI 1850, and the chlorophyte Mychonastes homosphaera ACOI 1850 had the highest scavenging activity. Cyanophytes revealed low antioxidant capacity, and mucilagineous strains of different taxa remained undetermined. The assessment of these strains and the broadening of a screening survey of the ACOI Culture Collection are expected to reveal very promising antioxidant-producing strains that may be applied in the field of human nutrition.