UHPLC-QQQ-MS/MS assay for quantification of dianthrones as&nbsp;potential toxic markers of Polygonum multiflorum Thunb: Application to the standardization of TCMs with endogenous toxicity
Authors: Yang Jian-Bo , Song Yun-Fei , Liu Yue , Gao Hui-Yu , Wang Qi , Wang Ying , Cheng Xian-Long , Zuo Tian-Tian , Hu Xiao-Wen , Wei Feng , Jin Hong-Tao , wang Shu-Ting , Ma Shuang-Cheng 
Published: April 2021

Abstract
Background: The raw and processed roots of Polygonum multiflorum Thunb (PM) are commonly used in clinical practice to treat diverse diseases; however, the reports of hepatotoxicity induced by Polygoni Multiflori Radix (PMR) and Polygoni Multiflori Radix Praeparata (PMRP) have emerged worldwide. Thus, it is necessary for researcher to explore the methods to improve its quality standards and further ensure its quality and treatment effect.Methods: In the present study, an ultra-high-performance liquid chromatography coupled with triple quadrupole mass spectrometry (UHPLC-QQQ- MS/MS) method has been optimized and validated for the determination of dianthrones in PMR and PMRP, using bianthronyl as the internal standard. Chromatographic separation with a gradient mobile phase (A: acetonitrile and B: water containing 0.1% formic acid (v/v)) at a flow rate of 0.25 mL/min was achieved on a Waters Acquilty UPLC BEH b) C18 column (2.1 mm × 50 mm, 1.7 µm). A triple quadrupole mass spectrometer (TQMS) was operated in negative ionization mode with multiple reaction monitoring for the quantitative analysis of six dianthrones. Meanwhile, compounds 5 and 6 were further evaluated for cytotoxicity of HepaRG cells by CCK8 assay.Results: The UHPLC-QQQ-MS/MS method was first developed to simultaneous determination of six dianthrones in PMR and PMRP, namely polygonumnolides C1–C4 (1–4), trans-emodin dianthrones (5), and cis-emodin dianthrones (6). The contents of 1~6 in 90 batches of PMR were in the range of 0.027-19.04, 0.022-13.86, 0.073 -15.53, 0.034 -23.35, 0.38-83.67 and 0.29 -67.00 µg/g, respectively. The contents of 1~6 in 86 batches of commercial PMRP were in the range of 0.020-13.03, 0.051-8.94, 0.022-7.23, 0.030 -12.75, 0.098-28.54 and 0.14-27.79 µg/g, respectively. The six dianthrones were almost completely gone after reasonable processing for 24 h. Meanwhile, compounds 5 and 6 showed the inhibitory activity against HepaRG cells with the IC50 values of 10.98 and 15.45 μM, respectively. Furthermore, a systematic five-step strategy to realize the standardization of TCMs with endogenous toxicity is proposed for the first time, involving the establishment of determination methods, determination of the toxic markers, the standardization of processing method, the development of limit standards and benefit-risk assessment.Conclusion: The results of cytotoxicity evaluation of dianthrone indicated that trans-emodin dianthrones (5) and cis-emodin dianthrones (6) could be selected as the toxic markers of PMRP. Taking PMR and PMRP for example, we hope this study provided insight into the standardization and internationalization of endogenous toxic TCMs, with the main purpose of improving public health by scientifically using TCMs to treat diverse complex diseases in future.