Stability of polyhydroxylated 1,4-naphthoquinone pigment recovered from spines of sea urchin Strongylocentrotus nudus

The stability of polyhydroxylated 1,4-naphthoquinone pigment recovered from sea urchin (Strongylocentrotus nudus) spines was observed by spectrophotometer. When pH values changed from 2.0 to 10.0, the pigment showed colour variations. Meanwhile, pH values affected the stability of the pigment. After 24 h of storage, the pigment remained 95.64%, 79.68% and 46.15% of the initial absorbance at pH 3.0, 7.0 and 10.0, respectively. The pigment was prone to degrade on exposure to light. It remained 40.11% of the initial absorbance under natural light after 14 days of storage. Whereas the corresponding value in the dark was 65.14%. Degradation rate of the pigment increased with increasing temperature. The pigment remained 90.49% of the initial absorbance at 20 degrees C after 24 h of storage. However, the corresponding value decreased to 66.61% at 80 degrees C. Additives, including antioxidant, oxidising and reducing agents, and some metal ions all affected the stability of the pigment.