pyrroloquinoline quinone2,4,6-tricarboxylic-pyrrolo[2,3-5,6]quinoline 8,9-quinone2,7,9-tricarboxy-1H-pyrrolo(2,3-f)quinoline-4,5-dione4,5-Dioxo-4,5-dihydro-1H-pyrrolo[2,3-f]quinoline-2,7,9-tricarboxylate4,5-dihydro-4,5-dioxo-1H-pyrrolo[2,3-5,6]quinoline-2,7,9-tricarboxylic acidMethoxatinPQQPYRROLOQUINOLINE QUINONEPyrrolo-quinoline quinonePyrroloquinoline quinonePyrroloquinoline-quinonecoenzyme PQQmethoxatin