NMR based metabolomic comparison of the antitussive and expectorant effect of Farfarae Flos collected at different stages

•The flower bud and the bloomed flower of Farfarae Flos were compared.•The compounds closely related with the activities of Farfarae Flos were identified.•The endogenous metabolites correlated with the function of FF were also identified.•The results are useful for explaining the rationality of the traditional use of FF.