Abstract
Some edible algae have been reported to contain substantial amounts of vitamin B_<12> but there is little information on bioavailability of the algal vitamin B_<12> for mammals. Thus, vitamin B_<12> was purified from various algae (including blue-green algae, cyanobacteria) and characterized to clarify the bioavailability of the algal compounds. The eukaryotic edible algae (green and purple lavers, Pleurochrysis carterae, and chlorella sp.) contained true vitamin B_<12>. Feeding of these algae to vitamin B_<12>-defecient rats significantly improved the vitamin B_<12> status, indicating that these eukaryotic algae are suitable sources as vitamin B_<12>, especially for vegetarians. All edible cyanobacteria tested (Spirulina sp., Aphanizomenon flos-aquae, Aphanothec sacrum, and Nostoc commune) predominately contain pseudovitamin B_<12>, which is inactive for mammals. Our studies indicate that these edible cyanobacteria have the ability to synthesize pseudovitamin B_<12>, which can mainly function as the coenzyme of the cobalamin-dependent methionine synthase involved in DNA synthesis.
