Novel Toxicokinetics and Metabolic Insights Into Arsenic in Biological Systems From Realgar-Indigo naturalis Formula

Realgar-Indigo naturalis Formula (RIF) is the only oral arsenic formulation approved globally and serves as a first-line treatment for acute promyelocytic leukemia (APL), and its safety profile remains a critical clinical concern though. Formulated according to the traditional Chinese medicine (TCM) compatibility principle known as "Jun-Chen-Zuo-Shi," the modern toxicokinetic rationale underlying the detoxifying or potentiating effects of its individual constituents on arsenic toxicity remains inadequately elucidated. In this study, we systematically evaluated arsenic toxicokinetic and methylation metabolism patterns in plasma and various tissues using high-performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (HPLC-ICP-MS), supplemented by histopathological examination via hematoxylin and eosin (H&E) staining. Compared with Realgar alone, Salvia miltiorrhiza Bunge and Pseudostellaria heterophylla markedly lowered immediate plasma AsV exposure by 62.8% and 51% and reduced tissue DMA burden by 58% and 23% in 9 days, respectively. In contrast, Indigo naturalis increased AsV exposure by 107% after 7 days and raised DMA burden in tissue by 19%. Overall, these toxicokinetic signatures indicate that S. miltiorrhiza Bunge and P. heterophylla confer a compatibility-dependent detoxifying effect, whereas I. naturalis potentiates arsenic toxicity. These toxicokinetic insights provide critical scientific evidence supporting the traditional compatibility principles, enhancing the safety and rational optimization of arsenic-based TCM formulations.