Marine species produce a wide range of bioactive peptides with potential nutraceutical and pharmaceutical value. They may act on the nervous, endocrine and immune systems. They are able to regulate appetite and stress. They also have antitumor and antiviral properties. Some are opioid-like and have a positive impact on our emotional status, motivation, behavior, anxiety and pain management [17]. They interact with specific opioid receptors and can stimulate the release of endogenous opioids like leucine and tryptophan. These peptides are a healthy alternative to opioid drugs which have side effects and are associated with addiction.
Bioactive peptides can be derived from the protein of marine species after extraction and hydrolysis processes in industrial-scale production. The use of non-toxic organic solvents, supercritical fluid extraction, microwave and ultrasound-assisted extraction, pulsed electric field assisted extraction and enzyme-assisted hydrolysis is preferred to avoid harsh chemical and physical treatment to preserve their functionality and nutritive values.
Marine collagen peptides are able to increase bone organic matrix, mineral density, osteoblastic activity and expression of osteogenic markers in a rat model of menopausal osteoporosis. They can stimulate chondrogenic differentiation and prevent the development of osteoarthritis [48]. A marine collagen-derived peptide with a high content of hydroxyproline (Pro-Gly-Pro-Asp-Lys-Pro) promotes cell viability and inhibits cell death by blocking potassium channels and oxidative stress. The neuropeptide terebrid toxin from the sea snail Terebra variegata is highly specific for arthropod voltage-gated sodium channels and has a distinct display compared with other marine snail neuropeptides. Pardaxin from the venom of the sea horse Hippocampus trimaculatus exerts a protective action against PC12 cell toxicity and enhances expression of prosurvival proteins [125]. The cyclic octapeptide reniochalistatin E from the marine sponge Reniochalina stalagmites has potent cytotoxic activity on HepG2 cells and S-180 tumor-bearing cancer cells with no effect on normal hepatocytes.