XanthineXanthic oxidePurine-2,6(1H,3H)-dioneXan3,9-Dihydro-1H-purine-2,6-dione1H-Purine-2,6-diolNSC 14664Isoxanthine1H,3H,7H-Xanthine3,9-Dihydropurine-2,6-dione9H-Purine-2,6(1H,3H)-dionePseudoxanthine1H,3H,9H-Xanthine2,6-Dioxo-1,2,3,6-tetrahydropurine2,6-DioxopurineXanthin