In Vitro Gastrointestinal Digestion Impact on the Antioxidant Activity of Extracts Produced from the Macroalgae <i>Gracilaria gracilis</i> and <i>Ulva rigida</i>

Abstract

The interest in edible algae has been growing over the years due to their richness in molecules with nutritional and bioactive potential, such as proteins, essential amino acids, vitamins and minerals. Furthermore, due to their interesting protein content, they have been described as a source of bioactive peptides, with scientifically documented antioxidant, anti-hypertensive and antimicrobial properties. In this work, water-soluble extracts were produced from the macroalgae Gracilaria gracilis and Ulva rigida, with focus on their antioxidant potential. Furthermore, the impact of in vitro gastrointestinal (GI) digestion on the antioxidant activity of both extracts was studied, with the goal of evaluating their potential as functional food ingredients. Extracts were produced by enzymatic hydrolysis, with a cellulase and a subtilisin protease, using a previously optimized method. Then, both were submitted to simulated GI conditions, similar to those found in the human digestive system. The antioxidant activity was determined by ORAC and ABTS assays in four stages of GI simulation (before digestion, and after mouth, stomach and intestine digestion). The antioxidant activity did not decrease throughout the different stages of digestion. Interestingly, the antioxidant capacity increased after some phases. For instance, both extracts presented higher ORAC values after all digestion phases, when compared to the non-digested extract, being statistically significant after stomach digestion, for G. gracilis extract (p G. gracilis and U. rigida extracts may be considered potential ingredients for the development of functional foods with antioxidant properties.

Keywords

• bioactive hydrolysates
• functional food
• active ingredients
• macroalgae
• marine species