Native and non-indigenous Mediterranean jellyfish as source of bioactive compounds

The phylum Cnidaria is a large, diverse and ecologically important group of marine invertebrates that includes over 11,000 extant species. Thousands of marine natural products have been described from this phylum alone, mostly in the last decade. The biotechnological potential of cnidarians started to attract the attention of researchers for their well-documented ability to produce powerful toxins and venoms. However, further research has shown that the biochemical biodiversity of cnidarians produces more classes of bioactive products. Furthermore, an increase in the number of blooms, individuals and the duration of outbreaks is also evident in the Mediterranean Sea. We studied three rhizostomeae jellyfish occurring in the Mediterranean Sea, the native Rhizostoma pulmo and Cotylorhiza tuberculata, and the non-indigenous species Cassiopea andromeda, for their biomass, potentially useful as human food, and their content of bioactive compounds, with antioxidant, immunomodulatory, and anti-proliferative activities on cancer cells. Structural proteins such as collagen, abundant in some thick-bodied species as R. pulmo, produce, by hydrolysis, antioxidant and anti-inflammatory peptides, while zooxanthellate jellyfish such as C. tuberculata and C. andromeda holobionts represent a source of powerful antioxidant and cancer-preventive compounds coming mainly from the endosymbiotic zooxanthellae. We discuss the potential application of jellyfish extracts and bioactive compounds as nutraceuticals, functional food, feed, and as source of bioactive compounds, in line with the goals of the blue-green and circular economy.