2022 年 39 巻 p. 8-12
To clarify the nutritional availability of iodine in seaweeds, the solubility and molecular species of iodine in several edible seaweeds were examined. The extraction rate of iodine from dry powdered seaweed samples by water or protease treatment was almost 100% for four species of kombu (Saccharina japonica, S. angustata, S. ochotensis, S. diabolica),but 37-88% for seaweeds other than kombu. In seaweeds other than kombu, some of the iodine may be either physically unextractable due to the cell walls or bound to insoluble substances. When the extracts obtained by protease treatment were analyzed by HPLC-ICPMS, iodide ions and iodoamino acids, monoiodotyrosine (MIT) and diiodotyrosine (DIT),were detected in all of them. In kombu, hijiki (Sargassum fusiforme),arame (Eisenia bicyclis), and wakame (Undaria pinnatifida, leaflike part),more than 90% of the iodine were iodide ions, whereas the proportions of MIT and DIT were relatively high in susabi-nori (Neopyropia yezoensis),hitoe-gusa (Monostroma nitidum), and mekabu (Undaria pinnatifida, root portion). In particular, more than 60% of iodine was iodoamino acids in susabi-nori which contains about 40% protein. In addition, several edible seaweeds contained unknown iodine compounds, although the amount ratios were small. These results indicate that iodine in powdered kombu is easily absorbed and effectively utilized.