Abstract: ¹H and ¹³C NMR spectra of polysubstituted xanthones and corresponding xanthone-O-glycoside, which are obtained from the plants of Qinghai-Xizang plateau,have been observed.The discussion are mainly focused on the relation between the chemical shifts and mode of substituted groups on 1,8 position of polysubstituted xanthone.¹H chemical shifts of substituted hydroxy on 1,8 position of xanthone have been summarised.The changes of chemical shift of carbon on xanthone ring caused by -O-sugar have been calculated and discussed.The result can be used to elucidate the structure of polysubstituted xanthone and xanthone-O-glycoslde.

Key words: Substituted xanthone, NMR, Xanthone-O-gycoside