Quantitative evaluation of Radix Paeoniae Alba sulfur-fumigated with different durations and purchased from herbal markets: simultaneous determination of twelve components belonging to three chemical types by improved high performance liquid chromatography-diode array detector.

•An improved HPLC–DAD method developed for quantification of three types of 12 major components in RPA.•Sulfur-fumigation duration affects chemical transformation extent of active component in RPA.•Sulfur-fumigation reduces the global quality consistency of both raw materials and decoctions of RPA.