MS m / z : 455 [ M ] +; 1 H - NMR ( 500 MHz , DMSO - d 6 ) : δ 6 . 07 ( 3 H , br s , H - 10 a , 12 a , 14 a ) , 6 . 23 ( 1 H , d , J = 2 . 0 Hz , H - 12 b ) , 6 . 54 ( 1 H , d , J = 16 . 4 Hz , H - 8 b ) , 6 . 55 ( 1 H , d , J = 2 . 0 Hz , H - 14 b ) , 6 . 67 ( 2 H , d , J = 8 . 5 Hz , H - 3 b , 5 b ) , 6 . 74 ( 2 H , d , J = 8 . 5 Hz , H - 3 a , 5 a ) , 6 . 84 ( 1 H , d , J = 16 . 4 Hz , H - 7 b ) , 7 . 11 ( 4 H , d , J = 8 . 5 Hz , H - 2 a , 6 a , 2 b , 6 b ) , 9 . 37 ( 5 H , br , D 2 O exchangeable OH ) ; 13 C - NMR ( 125 MHz , DMSO - d 6 ) : δ 131 . 7 ( C - 1 a ) , 127 . 0 ( C - 2 a , 6 a ) , 115 . 2 ( C - 3 a , 5 a ) , 157 . 2 ( C - 4 a ) , 92 . 3 ( C - 7 a ) , 55 . 0 ( C - 8 a ) , 146 . 0 ( C - 9 a ) , 105 . 5 ( C - 10 a , 14 a ) , 158 . 6 ( C - 11 a , 13 a ) , 101 . 0 ( C - 12 a ) , 127 . 9 ( C - 1 b ) , 127 . 7 ( C - 2 b , 6 b ) , 115 . 4 ( C - 3 b , 5 b ) , 157 . 3 ( C - 4 b ) , 128 . 9 ( C - 7 b ) , 122 . 0 ( C - 8 b ) , 134 . 8 ( C - 9 b ) , 118 . 5 ( C - 10 b ) , 160 . 7 ( C - 11 b ) , 95 . 9 ( C - 12 b ) , 158 . 4 ( C - 13 b ) , 103 . 1 ( C - 14 b ) .