Answer: flavin

AnswerCrossword Clue
flavinyellow, crystalline, slightly water-soluble powder, C15H10O7, obtained from the bark of the quercitron and other vegetable substances, used as a yellow dye; flavin
flavincomplex heterocyclic ketone that is common to the nonprotein part of several important yellow enzymes, the flavoproteins
flavina yellow pigment, also FLAVINE