The effect of drying on undervalued brown and red seaweed species: Bioactivity alterations

The effect of drying on two brown seaweed (Treptacantha abies-marina and Cystoseira humilis) and two red seaweed species (Asparagopsis armata and Asparagopsis taxiformis) was evaluated based on the levels of biological activity, such as antioxidant and anti-inflammatory properties. Moreover, the contents of some significant compound classes, such as polyphenols and beta-glucans, were determined. Seaweeds C. humilis and T. abies-marina showed high polyphenol levels (1.76–6.78 mg gallic acid equivalents g⁻¹ dw), which clearly exceeded those determined in the Asparagopsis genus regardless of drying process. This was partially reflected in the antioxidant activity as measured by DPPH and FRAP methods, which showed that extracts from C. humilis and T. abies-marina in most cases had stronger antioxidant activity than those from Asparagopsis species. The influence of the drying technique upon the antioxidant activity was relatively limited, since in many instances there was no effect. Concerning anti-inflammatory activity, in the case of shade-dried samples, C. humilis had a higher activity (>30% COX-2 inhibition) than A. armata. However, this activity in C. humilis was not rendered available in the upper gastrointestinal (GI) tract. Indeed, only A. taxiformis displayed anti-inflammatory activity in the fraction available in the upper GI tract, showing an upper GI tract availability in the 90–100% range. Therefore, though bioactivity levels were higher in C. humilis and T. abies-marina, Asparagopsis species also had substantial levels of bioactive compound. Sun-drying produced more negative effects than shade-drying, but these effects were not very extensive.