The vitamin B12 coenzymes are unstable in light. After consumption the cyanide ligand is replaced by other groups (adenosyl, methyl) to produce the biologically active forms. The cyanide is converted to thiocyanate and excreted by the kidney. Chemical reactions
In the cobalamins, cobalt normally exists in the trivalent state, Co(III). However, under reducing conditions, the cobalt center is reduced to Co(II) or even Co(I), which are usually denoted as B12r and B12s, for reduced and super reduced, respectively. B12r and B12s can be prepared from cyanocobalamin by controlled potential reduction, or chemical reduction using sodium borohydride in alkaline solution, zinc in acetic acid, or by the action of thiols. Both B12r and B12s are stable indefinitely under oxygen-free conditions. B12r appears orange-brown in solution, while B12s appears bluish-green under natural daylight, and purple under artificial light.B12s is one of the most nucleophilic species known in aqueous solution. This property allows the convenient preparation of cobalamin analogs with different substituents, via nucleophilic attack on alkyl halides and vinyl halides.For example, cyanocobalamin can be converted to its analog cobalamins via reduction to B12s, followed by the addition of the corresponding alkyl halides, acyl halides, alkene or alkyne. Steric hindrance is the major limiting factor in the synthesis of the B12 coenzyme analogs. For example, no reaction occurs between neopentyl chloride and B12s, whereas the secondary alkyl halide analogs are too unstable to be isolated.
In herpetic gingivostomatitis, lesions can be found in these locations, but they are almost always accompanied by ulcerations on the gums, lips, tongue or buccal mucosa and/or by hyperemia, hypertrophy or hemorrhage of the gums. Hand Foot and Mouth Disease: Similar to herpangina, hand foot and mouth disease occurs predominantly in children. It is caused by Coxsackie A and B virus, and lesions or blisters are found bilaterally on the hands, feet and mouth of the patient. Oral candidiasis: Also known as thrush, herpetic gingivostomatitis can often be differentiated from these microorganism/bacterial causing white plaques on the palate, buccal mucosa, tongue, oropharynx etc. Apthous stomatitis: They are commonly known as apthous ulcers, and are characterized by grey membranes and peripheral erythema. Lesions/ulcers for herpetic gingivostomatitis may also be found on the palate and keratinzied gingivae hence aphthous ulcers can be ruled out. Stevens–Johnson syndrome: Stevens–Johnson syndrome is characterized by early symptoms of malaise and fever, and shortly after that erythema, purpura and plaques on the skin, which often progresses to epidermal necrosis and sloughing in extreme cases. Infectious mononucleosis - Infectious Mononucleosis presents with a high fever and lymphadenopathy, which is may or may not be presented in the symptoms of herpetic gingivostomatitis. However, upon closer oral examination, ulceration, petechiae and occasional gingivostomatitis may be spotted. Behcets syndrome - It is an inflammatory disorder in which the presenting symptoms are recurrent aphthous ulcers, and severe cases may result in the patient having genital lesions, gastro-intestinal problems, and even arthritis.