Abstract: The exchange rate constants of the labile protons in quercetin with water and the selfdiffusion coefficients of quercetin in DMSOd6 solutions with different water concentrations and at different temperatures are studied. When the water concentration or the temperature is changed,both exchange rates and diffusion coefficients are changed,but there is no correlation between these two changes. This indicates that chemical exchange of the labile protons with water and selfdiffusion of the quercetin molecule are two independent motions in solutions and chemical exchange is not controlled by diffusion. However,the apparent selfdiffusion coefficients of the labile protons are obviously affected by chemical exchange.

Key words: Chemical exchange, Self-diffusion coefficients, Quercetin, Labile protons, NMR