Thermospray and electrospray mass spectrometry of flavocoenzymes. Analysis of riboflavin sulphates from sugar beet

Thermospray (TSP) liquid chromatography mass spectrometry and electrospray (ESP) mass spectrometry were applied to the analysis of the flavocoenzymes riboflavin (Rfv), riboflavin 5ʹ-monophosphate (FMN) and flavin adenine dinucleotide (FAD). Positive and negative ion spectra are presented. TSP spectra of Rfv and FMN were characterized by the presence of intense and characteristic fragment ions containing the flavin ring whereas in those from FAD, ions containing the adenine moiety predominate. ESP affords mainly molecular weight information as well as some indication of the number of acidic places in these molecules. Application of these techniques to the analysis of root extracts from iron-depleted sugar beet (Beta vulgaris) was instrumental in the characterization of two novel riboflavin compounds, riboflavin 3ʹ-monosulphate (3-FMS) and riboflavin 5ʹ-monosulphate (5-FMS), as the major flavins in roots.