Simultaneous determination of two anthraquinone-O-glucosides in five processed pieces from Rheum palamatum Simultaneous determination of two anthraquinone-O-glucosides in five processed pieces from Rheum palamatum A survey of microbial contamination for ten processed pieces of Chinese materia medica in Shanghai Variety regulation of aloe-emodin-3-CH2-O-β-D-glucopyranoside and emodin-8-O-β-D-glucopyranoside in five processed pieces from Rheum palmatum