Antioxidant potential of Atlantic sea cucumber (Cucumaria frondosa) processing byproducts

Orange-footed sea cucumber (Cucumaria frondosa) is abundant in the northwest Atlantic, boasting a wealth of bioactive compounds. The body wall is the major marketable portion of this echinoderm. However, during the processing, several visceral byproducts, including gonads, respiratory tracts, and intestines, along with or without tentacles/flower, are discarded as waste. These byproducts represent up to 50% of the sea cucumber biomass and are a rich source of bioactive compounds, mainly carotenoids and phenolics. This work aimed to examine the free, esterified, and insoluble-bound phenolics of sea cucumber processing byproducts using high-pressure processing (HPP) pre-treatment. The contents of total phenolics and flavonoids were determined, and antioxidant potential, including ABTS (2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid), DPPH (2,2-diphenyl-1-picrylhydrazyl), and hydroxyl radical scavenging activities, were assessed. The metal chelating ability of different phenolic fractions was also monitored. Furthermore, inhibition of LDL-cholesterol oxidation and DNA strand scission, as well as inhibition of tyrosinase, glycation, and α-glucosidase activity were investigated. Moreover, the antioxidant activity of phenolic extracts was evaluated in a fish model system using thiobarbituric acid reactive substance (TBARS) assay. It was found that sea cucumber processing discards serve as a good source of phenolic compounds. The highest amount of phenolics and antioxidant activity was observed in the free phenolic fraction upon HPP pre-treatment. Phenolic extracts improved the shelf-life of Atlantic salmon up to 9 days during refrigerated storage by inhibiting lipid oxidation. A strong positive correlation existed between total phenolics and various in vitro antioxidant assays, suggesting that sea cucumber phenolics have antioxidant potential. Additionally, 29 and 18 phenolic compounds were identified using UHPLC-QTOF/MS-MS from the free fraction of internal organs and tentacles, respectively, with phenolic acids and flavonoids being the predominant compounds.