This study investigates the capacity of phenolic extracts from microalgae Nannochloropsis sp. and Spirulina sp. to inhibit enzymes and free radical activities, intending to find an innovative way to slow down food damage. HPLC-UV and LC-MS/MS served to determine and confirm, respectively, the phenolic acid profiles in the soluble methanolic (free phenolic) and ethanolic (conjugated phenolic) fractions, and after hydrolysis (bound phenolic fractions). Different procedures measured the antioxidant activity of the extracts to estimate the minimal concentration for the protective effect, stability and versatility of activity. The ability to inhibit the oxidative process (ABTS and DPPH), α-amylase and peroxidase activities were estimated as specific inhibition (%/(min·μg)) for better comparison between the phenolic sources. The phenolic acid mass fractions in the free phenolic extracts from Spirulina sp. and Nannochloropsis sp. were 628 and 641 μg/g, respectively. Phenolic extract from Nannochloropsis sp. showed the highest value of ABTS inhibition (1.3%/(min·μg)) and highest inhibition of peroxidase activity (0.4%/(min·μg)). The extract from Spirulina sp. was a better inhibitor of α-amylase activity (0.07%/(min·μg)). Therefore, the phenolic extracts from the edible microalgae may be applied in food industry as natural protector against endogenous and exogenous hydrolytic and oxidative processes.
Keywords: Nannochloropsis sp.; Spirulina sp; amylase; antioxidant activity; peroxidase; phenolic extracts.