THE PHOTOCHEMISTRY OF RIBOFLAVIN—II. POLAROGRAPHIC STUDIES ON THE HYDROXYETHYL AND FORMYLMETHYL ANALOGS OF RIBOFLAVIN*

Abstract— The anaerobic photobleaching of 6, 7‐dimethyl‐9‐(2′‐hydroxyethyl)‐isoalloxazine, 9‐(2′‐hydroxyethyl)‐isoalloxazine and 6,7‐dimethyl‐9‐(formylmethyl)‐isoalloxazine have been compared. Polarographic and spectrophotometric techniques were used for rate studies. The methyl groups on the aromatic ring at the 6 and 7 positions affects the product distributtion in these simple flavins. Formylmethylflavin is postulated to undergo a bimolecular photoredox reaction which is novel to flavin photochemistry. It was demonstrated that there is a common type of leucoflavin formed during anaerobic photobleaching of riboflavin, formylmethylflavin and hydroxyethylflavin. This leucocompound also formed during the photoreduction of formylmethylflavin but not during the photoreduction of the other flavins.