抄録
Substantial amounts of vitamin B_<12> were found in some edible algae (green and purple lavers) and algal health food (chlorella and spirulina tablets and so on). Vitamin B_<12>-compounds were purified and characterized from these edible algae to clarify the chemical properties and bioavailability of the algal vitamin B_<12>. True vitamin B_<12> is the predominate cobamide of the eukaryotic algae (green and purple lavers and chlorella sp.). Feeding the purple laver to vitamin B_<12>-deficient rats or humans significantly improved the vitamin B_<12> status. Although these eukaryotic algae consist of both species with or without vitamin B_<12>-requirement, both of them have the ability to take up and accumulate exogenous vitamin B_<12>; there is little information available on physiological function of vitamin B_<12> in the algae. Pseudovitamin B_<12> (an inactive corrinoid compound) predominated in all edible cyanobacteria tested, Spirulina sp., Nostoc commune (Ishikurage), Aphanothece sacrum (Suizenji-nori), and Aphanizomenon flosaquae. They are not suitable for use as a vitamin B_<12> source, especially for vegetarians. Some of these edible cyanobacteria have the ability to de novo synthesize pseudovitamin B_<12>, which can mainly function as the coenzyme of cobalamin-dependent methionine synthase involved in DNA synthesis.
