1 H - NMR ( DMSO - d 6 , 400 MHz ) δ : 6 . 15 ( 1 H , d , J = 2 . 2 Hz , 6 - H ) , 6 . 44 ( 1 H , d , J = 2 . 6 Hz , 8 - H ) , 7 . 07 ( 3 H , m , 5 '- H , gallic acid ) . 7 . 89 ( 1 H , s , 2 '- H ) , 7 . 94 ( 1 H , s , 6 '- H ) , 12 . 39 ( 1 H , s , 5 - OH ) ; HRMS calcd . for C 22 H 15 O 11 455 . 0614 , found 455 . 0608 .