Release of bioactive peptides by simulated gastrointestinal digestion of sea cucumber protein (Isostichopus Badionotus)

Abstract

[Introduction]: Sea cucumber is widely consumed as a putative functional food. Three sea cucumber species predominate off the coasts of the Yucatan Peninsula in southeast Mexico. Of these, Isostichopus badionotus is captured most intensively due to its turgid body wall, a desirable trait on international markets. The body wall is generally consumed after boiling of previously dried and salted organisms. It contains many biologically active substances, but only limited research on its properties in vivo has been done, mainly investigating nutritional value and the hypocholesterolemic effect. However, no data about activity of peptides released from Sea cucumber protein hydrolyzed under conditions simulating gastrointestinal digestion have been reported to date. [Objectives]: The main aim of this work was to evaluate the biological activities of peptides released from Sea cucumber (Isostichopus badionotus) under simulated gastrointestinal digestion conditions. [Method/Design]: Sea cucumber Isostichopus badionotus (Holoturia) were collected from the sea floor off the coast of Sisal, Yucatan state, Mexico and cooked in water for 1 h at 100°C followed by lyophylization. It was then processed with a two-stage in vitro enzymatic procedure simulating physiological digestion. First, the sea cucumber was digested with pepsin at pH 2.0 and 37 ºC for 90 min. The enzyme was inactivated, the enzyme Corolase PP added, and the mixture incubated for 240 min at pH 7.5 and 37 ºC. Aliquots were taken after the pepsin and Corolase PP digestions, centrifuged and subjected to ultra-filtration through a hydrophilic 3000 Da cut-off membrane. Different biological activities were analyzed in the hydrolyzates and the <3kDa and >3kDa fractions. Antioxidant activity was determined using two in vitro assays, oxygen radical scavenging capacity, and Fe3+ to Fe2+ reduction capacity. Angiotensin-converting enzyme inhibitory, antithrombotic, hypocholesterolemic and anti-proliferative activities were also analyzed. [Results]: Hydrolyzates obtained from Sea cucumber hydrolyzed under simulated gastrointestinal digestion conditions exhibited potent in vitro antioxidant activity through different action mechanisms. Peptides released from pepsin and Corolase PP action were able to scavenge oxygen radicals and to reduce iron. Preliminary studies are showing that peptides generated after gastrointestinal digestion exert a notable angiotensin-converting enzyme inhibitory activity. [Conclusions]: Sea cucumber protein is a promising source of biological peptides after simulated gastrointestinal digestion. Different activities demonstrated for these peptides increase the high nutritional and functional value of this animal, making it a promising functional food.