Isolation of an antioxidant naphthoquinone from coelomic fluid of the Antarctic Sterechinus neumayeri sea urchin

The low temperatures and high concentrations of dissolved oxygen in the Antarctic marine environment could favor the presence of antioxidant molecules in animals, for scavenging of free radicals. In this study, we report the isolation of a novel antioxidant molecule from the Antarctic sea urchin Sterechinus neumayeri using an activity-guided fractionation approach. S. neumayeri specimens were collected near the South Shetland Islands (coordinates: 62°09.568’S 58°26.959’W and 62°12’12.2’’S 58°56’41.7’’W) in November 2018. Their coelomic fluid was extracted and fractionated by solid-phase extraction. The fraction exhibiting activity in the DPPH assay (a common method for measuring antioxidant capacity) was further purified using RP-HPLC (reverse-phase high-performance liquid chromatography). Subfractions were then tested in three different antioxidant assays (DPPH, hydrogen peroxide, and hydroxyl radical). One fraction displayed activity in all assays, suggesting a potent antioxidant. Mass spectrometry analysis predicted this molecule to be a naphthoquinone. While naphthoquinones have been identified in tropical sea urchins, this is the first report of an antioxidant molecule with a radical scavenging mechanism isolated from an Antarctic sea urchin. This finding suggests the molecule plays a crucial role in the sea urchin’s adaptation to the harsh Antarctic environment, where ROS formation is enhanced.