InChI=1S/C18H16O8/c19-12-4-1-11(8-13(12)20)9-16(18(24)25)26-15-5-2-10(7-14(15)21)3-6-17(22)23/h1-8,16,19-21H,9H2,(H,22,23)(H,24,25)/b6-3+