Simultaneous quantitative determination of six active compounds from Paeoniae Rubra Radix and Paeoniae Alba Radix by HPLC Absorption and transport characteristic of paeoniflorin and its derivatives in model of Caco-2 cell monolayers Chemical constituents from rhizomes of Paeonia sinjiangensis Studies on chemical constituents in Guizhi Fuling Capsule (V) Determination of chemical components of Paeoniae Radix Alba decoction pieces and its quality evaluation