*Article* **The Jellyfish** *Rhizostoma pulmo* **(Cnidaria): Biochemical Composition of Ovaries and Antibacterial Lysozyme-like Activity of the Oocyte Lysate**

**Loredana Stabili 1,2,\*, Lucia Rizzo 3,4, Francesco Paolo Fanizzi 1, Federica Angilè 1, Laura Del Coco 1, Chiara Roberta Girelli 1, Silvia Lomartire 1, Stefano Piraino 1,3,\* and Lorena Basso 1,3,\***


Received: 18 October 2018; Accepted: 23 December 2018; Published: 29 December 2018

**Abstract:** Jellyfish outbreaks in marine coastal areas represent an emergen<sup>t</sup> problem worldwide, with negative consequences on human activities and ecosystem functioning. However, potential 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<sup>−</sup><sup>1</sup> and 45.7 ± 1.5%), lipids (192.17 ± 10.56 μg mg<sup>−</sup><sup>1</sup> and 9.6 ± 0.6%), and carbohydrates (59.66 ± 2.72 μg mg<sup>−</sup><sup>1</sup> and 3.7 ± 0.3%). 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), diunsaturated 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 gran<sup>t</sup> 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 an exploitation of *R. pulmo* biomasses as a resource of bioactive metabolites of biotechnological importance including pharmaceuticals and nutrition.

**Keywords:** antibacterial activity; NMR spectroscopy; biochemical characterization; jellyfish blooms
