A Novel Bitter Amino Acid, Pulcherrimine Isolated From Sea Urchin Ovaries: Relationship Between Maturation And Their Contents

The present study was undertaken to unders the properties and origins of the bitter substance in the sea urchin gonads and the relationship between maturation and their contents. The frequency of occurrence of bitter-tasting sea urchins collected in the sea off Iwaki, Fukushima Prefecture was examined first. The bitterness was found to be specific to mature ovaries. From the mature ovaries, a bitter substance was isolated and the structure was determined to be 4S-(2’-carboxy-2’S-hydroxy-ethylthio)-2Rpiperidinecarboxylic acid, being a novel sulfur-containing amino acid, named pulcherrimine (Pul). Subsequently, we investigated the seasonal changes in the frequency of occurrence of mature female sea urchins and the frequency distribution of Pul contents among the mature female individuals at Iwaki, Fukushima Prefecture. Many mature individuals with high Pul-containing ovaries were found in all months examined in this area. From these findings, it was concluded that the presence of mature individuals with a high amount of Pul in all seasons is the major reason why sea urchins are hardly utilized as food in this area. In Mikuni, Fukui Prefecture, we investigated the relationship between the reproductive cycle and content of Pul in the ovaries of the sea urchin. From May to September, most of the individuals had immature gonads (stage 1), in which Pul was not detected. Many individuals were in stage 2 (growing) in October, and in stage 3 (pre-mature) in November. Pul content in the ovaries gradually increased during this period. In December and February, all the individuals were in stage 4 (mature). After the rapid decrease in GI, many individuals were in stage 5 (spent) in