Antioxidants in digestive tracts and gonads of green urchin (Strongylocentrotus droebachiensis)

Digestive tracts and gonads of green urchin (Strongylocentrotus droebachiensis) were evaluated for their antioxidant potential and total phenol and flavonoid contents. Antioxidant potentials of freeze-dried samples were evaluated using lipophilic and hydrophilic oxygen radical absorbance capacity (ORAC) assays. Analyzed samples showed antioxidant activity with total ORAC values of 864 and 885 μmol of TE/g d.w. for digestive tracts and gonads, respectively. Acetonitrile-rich and ethyl acetate extracts from freeze-dried samples showed ORAC values (1500-2100 μmol of TE/g) higher than crude tissues (∼870 μmol of TE/g), while water-rich extracts were less active (260-370 μmol of TE/g). Eluates 1 and 2 obtained from C₁₈ solid-phase extraction of the water-rich fraction showed ORAC values (650-1600 μmol of TE/g) up to 6 times higher than their parent extracts. Total phenol and flavonoid contents of freeze-dried samples ranged from 53 to 123 mg of GAE/100 g d.w. and 1.4-1.8 mg of RE/100 g, respectively. ORAC values from digestive tracts samples showed significant correlations with total phenols (r² = 0.76, p = 0.049, n = 12) and flavonoids (r² = 0.80, p = 0.021, n = 12), while a very weak correlation was observed for samples from gonads. This is the first study to quantify antioxidant properties of green urchin tissues, and show that edible gonads might provide valuable antioxidants to consumers while digestive tracts might be valorized as an alternative source of antioxidants in food additive ingredients.