Characterization of alkyl-cobalamins formed on trapping of epoxide metabolites of 1,3-butadiene

Analytical methods facilitating studies of electrophilically reactive and genotoxic compounds in vitro and in vivo are needed. The strong nucleophile, cob(I)alamin, formed by reduction of Vitamin B12 [cob(III)alamin], may be used for trapping and analysis of 1,2‐epoxides and other electrophiles. In the present study, cob(I)alamin is evaluated as an analytical tool for 1,2‐epoxide metabolites (oxiranes) of 1,3‐butadiene. Products of reaction of cob(I)alamin with 1,2‐epoxy‐3‐butene (EB), 1,2:3,4‐diepoxybutane (DEB), and 1,2‐epoxy‐3,4‐butanediol (EBdiol) have been analyzed by reversed phase high performance liquid chromatography (HPLC) coupled on‐line to electrospray ionization mass spectrometry (ESI‐MS) and ultraviolet diode array detection (UV‐DAD). It was shown that a specific alkyl‐Cbl complex is formed for each metabolite and that it was possible to discriminate between the products by HPLC‐UV and by LC‐MS. Quantification of DEB with the method by use of another 1,2‐epoxide as an internal standard was successfully performed. The possibility of using cob(I)alamin for trapping and analysis of the three oxirane metabolites of 1,3‐butadiene will facilitate quantitative comparisons of species in vitro with regard to metabolism of 1,3‐butadiene.