Polyhydroxynaphtoquinone pigments from sea urchins waste: strategies for biomass valorization

In the last decades, the demand for sea urchins from food industry, is increasing 1. Most of them come from natural stocks, thus resulting in large environmental impact. In this framework, the CIRCULAr and BRITEs projects aim to fully reuse wastes from edible sea urchin industry to convert them, according to the logic of circular economy, into products with high added-value, including materials for biomedical applications and feed supplements to sustain sea urchin aquaculture, a valid alternative to overcome their overexploitation. For this purpose, sea urchins wastes from some Milan’s restaurants were finely grinded to produce a powder that could be a valuable additive to the feed for animals requiring high doses of carbonates, like hens and sea urchins themselves. The powder was characterized in its mineral and pigments content. In fact, pigments contained in Paracentrotus lividus, the species under investigation, are of high interest. They belong to the family of polyhydroxynaphthoquinones, a class of small polyphenols, and are natural antioxidants with potential health benefits. Pigments were obtained from sea urchin powder by means of solvent-based extraction procedures, performing treatments with aqueous acidic solution to decompose the carbonates matrix, and then a counter-extraction with selective organic solvents 2. The presence of high amount of polyphenols in the extract was confirmed with Folin-Ciocalteau assay and its antioxidant activity was assessed by ABTS assay (2,2’-azino-bis(3-ethylnenzothiazoline-6-sulfonic acid), being comparable to the one of Trolox®, used as reference antioxidant in the literature. The extract was then characterized by Ultraperformance Liquid Chromatography coupled to Mass Spectrometry, and the presence of Spinochrome A and Spinochrome B was confirmed. Furthermore, having in mind future biomedical applications, cytotoxicity of the pigments was tested in vitro with MTT assay using human dermal fibroblasts. No evidence of cytotoxicity was observed. The developed extraction strategy allows to obtain a product of high added value useful to be employed as feed additive or in other health sectors.