Commercial Red Seaweed in Portugal ( Gelidium sesquipedale and Pterocladiella capillacea , Florideophyceae): Going beyond a Single-Purpose Product Approach by Valorizing Bioactivity

The red seaweed species Gelidium sesquipedale and Pterocladiella capillacea are commercially explored as one of the main seaweed resources in Portugal. However, they are essentially harvested for extraction of agar, leaving a large biomass share needing an adequate valorization. The two studied red seaweed species were characterized by a large share of saturated fatty acids (SFA) in the vicinity of 60% (of the total FAs). Concerning ω3 highly unsaturated FAs, only EPA reached a significant percentage in P. capillacea and G. sesquipedale, 13.0 ± 0.5% and 7.7 ± 0.1%, respectively. In comparison with other seaweeds, the phenolic content was low for both species and aqueous and ethanolic extracts. The antioxidant activity was also low or even undetected. Regarding anti-inflammatory activity, as measured by inhibition of cyclooxygenase-2, it was not detected in the aqueous extracts of the seaweed, but was significant in the ethanolic extracts, 69 ± 3% and 54 ± 6%, for P. capillacea and G. sesquipedale, respectively. Concerning cytotoxicity, while ethanolic extracts did not cause any detectable cytotoxicity, the biomass and the aqueous extracts reduced HeLa cell viability. Finally, the elemental composition showed differences between the two seaweed species. In particular, G. sesquipedale contained a higher I level than P. capillacea, 807 ± 51 mg/kg dw vs 435 ± 18 mg/kg dw. On the whole, attained results were promising and warrant further study.