Photochemical reactions of formylmethylflavin and riboflavin

ABSTRACT

Formylmethylflavin [FMF] is a major intermediate product in the aerobic and anaerobic photolysis of riboflavin [RF] and is highly sensitive to light and hydrolysis. It is more sensitive to light as compared to RF. FMF is further degraded into lumichrome [LC], carboxymethylflavin [CMF] in acidic medium, and LC, CMF and lumiflavin [LF] in alkaline medium. When FMF is exposed to light it is degraded in to LC and LF via a photoreduction and CMF through photooxidation pathways. In aerobic and anaerobic conditions, RF when exposed to light is excited to singlet state [1RF] and from singlet to triplet state [3RF]. This is followed by the conversion of 3RF into a semiquinone radical [RFH] and this radical further disproportionate to form an oxidized RF and a cyclic intermediate, which is further oxidized to FMF and degradation products [LC, LF, CMF]