eTo isolate and identify the chemical constituents in the rhizome of the Petasites japonicus.MethodsDried rhizome of Petasites japonicus were subjected to extraction with EtOH,and the chemical constituents in the extract were isolated and their structures were identified by physicochemical properties and spectral analysis.ResultsFive compounds were obtained and identified from the rhizome of Petasites japonicus,inlcuding as β-sitoterol(Ⅰ) ,ergosterol (Ⅱ), bakkenolide-B (Ⅲ), bakkenolide-D (Ⅳ) and furanofukinol (Ⅴ).ConclusionCompound(Ⅱ) has been obtained from Petasites japonicus for the first time.