posted on 2016-02-19, 21:49authored byZi-Ming Feng, Jun He, Jian-Shuang Jiang, Zhong Chen, Ya-Nan Yang, Pei-Cheng Zhang
Hydroxysafflor yellow A (HSYA), a representative component
of Carthamus tinctorius, has attracted much attention
because
of its remarkable cardiovascular activities. Its structure was originally
reported in 1993 and has been widely cited to date. In our experiments,
its solution structure was studied using NMR techniques in different
solvents, including DMSO-d6, pyridine-d5, and CD3OH. The results indicate
that the structure of HSYA is different than the previously described 1b, with 3-enol-1,7-diketo form. The structure has two keto–enol
tautomers (2a and 2b), and 2a, with the 1-enol-3,7-diketo form, is the preferred tautomer. On
the basis of this finding, other published quinochalcone C-glycoside
structures were revised. Furthermore, a trend in the 13C NMR data of the (E)-olefinic carbons of quinochalcone
C-glycosides is summarized, and a hypothesis is proposed for the relationship
between the features of the molecular structure and the preferred
keto–enol tautomer.