Jellyfish outbreaks in marine coastal areas represent an emergent problem worldwide, with negative consequences on human activities and ecosystem functioning. However, potentially positive effects of jellyfish biomass proliferation may be envisaged as a natural source of bioactive compounds of pharmaceutical interest.

We investigated the biochemical composition of mature female gonads and lysozyme antibacterial activity of oocytes in the Mediterranean barrel jellyfish Rhizostoma Pulmo. Chemical characterization was performed by means of multinuclear and multidimensional NMR spectroscopy.

The ovaries of R. Pulmo were mainly composed of water (93.7 ± 1.9% of wet weight), with organic matter (OM) and dry weight made respectively of proteins (761.76 ± 25.11 µg mg−1 and 45.7 ± 1.5%), lipids (192.17 ± 10.56 µg mg−1 and 9.6 ± 0.6%), and carbohydrates (59.66 ± 2.72 µg mg−1 and 3.7 ± 0.3%).

Antibacterial lysozyme-like activity

The aqueous extract of R. pulmo gonads contained free amino acids, organic acids, and derivatives; the lipid extract was composed of triglycerides (TG), polyunsaturated fatty acids (PUFAs), di-unsaturated fatty acids (DUFAs), monounsaturated fatty acids (MUFAs), saturated fatty acids (SFAs), and minor components such as sterols and phospholipids.

The R. Pulmo oocyte lysate exhibited an antibacterial lysozyme-like activity (mean diameter of lysis of 9.33 ± 0.32 mm corresponding to 1.21 mg/mL of hen egg-white lysozyme).

The occurrence of defense molecules is a crucial mechanism to grant healthy development of mature eggs and fertilized embryos (and the reproductive success of the species) by preventing marine bacterial overgrowth.

As a corollary, these results call for future investigations for exploitation of R. Pulmo bio-masses as a resource of bioactive metabolites of biotechnological importance including pharmaceuticals and nutrition.

In conclusion, R. Pulmo ovaries and oocytes could represent a promising source of bioactive compounds for different applications mainly in the pharmaceutical field or as specialty feed.

In particular, the antibacterial lysozyme-like activity suggests that this jellyfish species may represent a new and renewable resource for drugs discovery. Moreover, the presence of ω-3 PUFAs encourages their potential exploitation as sources of these compounds in the production of fish feed.

Further studies will help to standardize a sustainable exploitation pilot system to use different jellyfish fractions for different purposes (e.g., food, feed) and beneficial services for human well-being.