Document Detail


Conversion of hydroxo(aquo) cobalamin to sulfitocobalamin in the absence of light: a reaction of importance in the identification of the forms of vitamin B12, with possible clinical significance.
MedLine Citation:
PMID:  562065     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
During determinations of the forms of vitamin B12 in foods and human tissues several samples yielded a growth zone on bioautography which was distinct from those due to methylcobalamin, adenosylcobalamin, hydroxocobalamin, or cyanocobalamin. The material responsible for this growth zone was identified as sulfitocobalamin and the mechanisms in its formation from hydroxocobalamin involve absence of light and the presence of bisulphite ions derived from atmospheric sulfur dioxide or indigenous sulfite ions. The formation of sulfitocobalamin during the extraction of cobalamins from foods and tissues can be prevented by reception and homogenization of the material in an ammonia buffer instead of water; the hydroxocobalamin is then converted to ammonia cobalamin, which is more resistant to attack by (bi)sulfite ions. The conversion of hydroxo(aquo)cobalamin to sulfitocobalamin in the dark can be rapid, and materials for analysis should be placed in the ammonia buffer before darkroom work is begun. The rapid conversion of hydroxo(aquo)cobalamin to sulfitocobalamin in the dark raises the possibility that hydroxocobalamin in foods may be converted to the less well absorbed sulfitocobalamin in the upper gastrointestinal tract.
Authors:
J Farquharson; J F Adams
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  The American journal of clinical nutrition     Volume:  30     ISSN:  0002-9165     ISO Abbreviation:  Am. J. Clin. Nutr.     Publication Date:  1977 Oct 
Date Detail:
Created Date:  1977-11-30     Completed Date:  1977-11-30     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0376027     Medline TA:  Am J Clin Nutr     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1617-22     Citation Subset:  AIM; IM    
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MeSH Terms
Descriptor/Qualifier:
Animals
Cattle
Chemical Phenomena
Chemistry
Darkness
Drug Stability
Food Analysis*
Hydroxocobalamin* / analysis
Light
Liver / analysis
Meat / analysis
Milk / analysis
Milk, Human / analysis
Sheep
Sulfites
Vitamin B 12* / analogs & derivatives,  analysis
Chemical
Reg. No./Substance:
0/Sulfites; 13422-51-0/Hydroxocobalamin; 68-19-9/Vitamin B 12

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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