After chlorination, DBP-423 was involved in additional hydroxylations yielding DBP-424, DBP-859A and DBP-859B. Molecular formula of DBP-424 differed from DBP-423 by the loss of a CH2 group (O-demethylation) and addition of one oxygen Go 6976 (epoxidation). The most probable position of the epoxide would be in the double bond of the vindoline moiety. DBP-859 differed from DBP-423 only in the loss of two hydrogen atoms and the addition of one oxygen atom. RDB of DBP-859 indicated an unsaturation more than DBP-423. In addition, the fact that the doubly charged ion was not observed in the spectrum indicated that one of the nitrogen atoms was less basic. So, the reaction mechanism conducting to this DBP might be similar to that previously discussed for DBP-785 and DBP-769, and for DBP-839 of VCN. Chromatographic responses for chlorinated DBPs represented less than 13% of the VBL peak area in the reference experiment, whereas some non-chlorinated DBPs reached up to 30% of the parent compound ( Fig. 4). No di-halogenated compounds were detected as DBPs of VBL. MS/MS spectra for selected DBPs of VBL are displayed in Fig. S3 (Supplementary information).