isoriboflavin

i·so·ri·bo·fla·vin

(ī'sō-rī'bō-flā'vin), 8-Demethyl-6-methylriboflavin; a riboflavin antimetabolite, differing from riboflavin in that the methyl groups on the isoalloxazine nucleus are in the 6,7 positions rather than the 7,8.