Vitamin B12 and derivatives--In vitro permeation studies across Caco-2 cell monolayers and freshly excised rat intestinal mucosa.

The purpose of this study was to compare the intestinal permeation of vitamin B12 and various derivatives thereof. Permeation behavior and cytotoxicity of four derivatives (coenzyme B12, hydroxocobalamin, methylcobalamin and 4-ethylphenylcobalamin) in comparison to vitamin B12 were evaluated in two different in vitro models, Caco-2 cells and freshly excised rat intestinal mucosa. Resazurin assay was used to evaluate cytotoxicity of the test substances. All test compounds were used at a concentration of 200 µg/ml. Permeation experiments were carried out for 3h and test compounds were quantified via reversed phase high performance liquid chromatography (HPLC). Cytotoxicity studies showed all test compounds are not toxic to cells. HPLC analyses of test compounds revealed the following rank order of increasing hydrophobicity: hydroxocobalamin