Green extraction of phenolic compounds and carrageenan from the red alga Kappaphycus alvarezii

Kappaphycus alvarezii (KA) is a widespread worldwide alga, and one of the main industrial sources of carra-geenan. Besides, KA biomass also contains other substances such as phenolic compounds and fatty acids that can be recovered by several methods. Then, this work aimed to investigate the eco-friendly methods, for the recovery of fatty acids, phenolics, and carrageenan fractions. The eco-friendly methods are faster, produce higher yields, and can be cost-effective in comparison with conventional methods. The performance of the eco-friendly methods (supercritical fluid, pressurized liquid, microwave assisted, and high-pressure carrageenan extrac-tions) was compared with conventional techniques (maceration or Soxhlet) in terms of yield, chemical profile by gas and liquid chromatography, total phenolic content (TPC), antioxidant activity by 1,1-diphenyl-2-picrylhydra-zyl (DPPH) and Ferric reducing antioxidant power (FRAP) procedures, viscosity and gel strength of the carra-geenan fraction. The results showed pressurized liquid extraction samples with the highest antioxidant potential and TPC (up to 2 to 4 times higher than conventional). Besides, the carrageenan fraction was efficiently recovered by microwave assisted extraction (MAE) and by pressurized-water carrageenan extraction (PWCE), and the samples presented viscosity and gel strength similar to that obtained by water maceration.

Automated summary

This study investigated eco-friendly methods for the recovery of fatty acids, phenolics, and carrageenan fractions, which are faster, produce higher yields, and can be cost-effective compared to conventional methods. Pressurized liquid extraction showed the highest antioxidant potential and total phenolic content, while microwave-assisted extraction and pressurized-water carrageenan extraction efficiently recovered the carrageenan fraction.