Emodin

Standards of chrysophanol, emodin, aloe-emodin, rhein, physcion, questin, TSG, emodin-8-O-β-D-glucoside (EG), physcion-8-O-β-D-glucoside (PG), and puerarin (IS) were purchased from the Chengdu Chroma-Biotechnology Co., Ltd. (Chengdu, China). Citreorosein, questinol, torachrysone-8-O-glucoside (TG), and chrysophanol-8-O-β-D-glucoside (CG) were purchased from the Qingdao Advancechem Technology Co., Ltd. (Qingdao, China). The chemical structures of the 13 constituents of RPM and IS are shown in Figure 1.
RPM was purchased from Beijing Tongrentang Pharmaceutical Co., Ltd, and identified by professor Shuofeng Zhang (Beijing University of Chinese Medicine). The voucher specimen (lot no.: YDZY-HSW-20180521) was deposited at 4°C in our laboratory. The RPM (200 g) was refluxed with 70% ethanol twice (1 : 10, w/v), 3 h for each time. All the solution obtained were put together and condensed by vacuum drier at 50°C to get 50 ml extract, containing 4 g raw herb per milliliter.
LC-grade acetonitrile and formic acid were purchased from Honeywell (Morristown, USA) and Roe Scientific Inc. (Newark, USA), respectively. Ultra-pure water was prepared using a Millipore Milli-Q purification system (Bedford, USA).

The herb of P. capitatum was collected from Qianxi county, Guizhou province, China and was identified by Qingde Long (Guizhou Medical University) as the whole plant of Polygonum capitatum Buch.-Ham. ex D. Don. The voucher specimen of P. capitatum (No.: PC20201103) was deposited in the Herbarium of Guizhou Medical University.
The reference standards of gallic acid, protocatechuic acid, (+)-catechin, rutin, quercitrin, quercetin and emodin were purchased from Chengdu Chroma-Biotechnology Co., Ltd. (Chengdu, China). The pure materials of myricitrin, quercetin-3-O-(2″-O-galloyl)-β-d-glucopyranoside, quercetin-3-O-β-d-glucopyranoside, cis-N-caffeoyltyramine and 3″-O-galloylquercitrin were obtained in our laboratory. The purities of the reference standards were determined to be more than 98% by HPLC (-DAD. Hypoxanthine and potassium oxonate were purchased from the Beijing Solarbio Science and Technology Co., Ltd. (Beijing, China). Urate assay kits were purchased from Nanjing Jiancheng Bioengineering Institute (Nanjing, China).
HPLC-grade methanol and acetonitrile were acquired from Honeywell Burdick & Jackson Company (Morristown, NJ, USA). Formic acid (MS grade) was obtained from Fisher Scientific (Madrid, Spain). Deionized water for HPLC analysis was prepared using a Milli-Q water purification system (Millipore, Milford, MA, USA). All other reagents were of analytical grade.

The dried herbal roots of Reynoutria multiflora (Thunb.) Moldenke (Polygonaceae) (RPM) were purchased from Beijing Tongrentang Pharmaceutical Co., Ltd. The raw materials were carefully authenticated by one of the authors, Prof. Shuofeng Zhang. The voucher specimen (lot no: YDZY-HSW-20180521) was deposited in a refrigerator at 4°C. Chrysophanol, emodin, aloe-emodin, rhein, physcion, questin, emodin-8-O-β-D-glucoside (EG), physcion-8-O-β-D-glucoside (PG), 2,3,5,4′-teterahydroxystilbene-2-O-β-D-glucoside (TSG), and puerarin (IS) were obtained from Chengdu Chroma-Biotechnology Co., Ltd. (Chengdu, China). Citreorosein, questinol, torachrysone-8-O-glucoside (TG), and Chrysophanol-8-O-β-D-glucoside (CG) were purchased from Qingdao Advance Chem Technology Co., Ltd. (Qingdao, China). The purity of the various compounds was 98% (Figure 1). Sodium carboxymethyl cellulose (CMC-Na) was purchased from Sinopharm Chemical Reagent Co., Ltd (Shanghai, China). LC-grade acetonitrile and formic acid were purchased from Honeywell (Morristown, United States) and Roe Scientific Inc. (Newark, United States), respectively. Ultra-pure water was prepared using a Millipore Milli-Q purification system (Bedford, United States).