Extraction and identification of antioxidant polyhydroxynaphthoquinone pigments from the sea urchin, Psammechinus miliaris

- Antioxidant pigments were extracted from the tests of a common edible sea urchin.
- UV spectra properties and LC-MS analysis identified them as polyhydroxynaphthoquinones.
- Structures were similar to previous reports but with evidence for novel sulphated forms.

Pigments were extracted from tests of individual sea urchins, Psammechinus miliaris, collected from a sea loch in Scotland. The extracts were red brown-to-orange in colour and yielded UV spectra with maxima at 475, 320 and 270 nm characteristic of polyhydroxylated naphthoquinone pigments (PHNQs) identified in other sea urchins. The yield of total phenols from the tests was relatively low (1-2 mg/g dry weight) but in line with levels found in tests from other sea urchin species. The extracts displayed reasonable antioxidant capacity assayed using the FRAP assay.After selection by solid phase extraction, the extracts were analysed by liquid chromatography-mass spectrometry (LC-MS). The LC-MS data suggested that the pigmentation was due to a range of spinochrome and echinochrome PHNQ components. Most of these components have been noted previously but there was evidence for sulphated forms which have not been identified before. The role and potential utility of these pigments in food applications is discussed.