Traditional Chinese Medicine (TCM) is widely recognized for its extensive historical roots and diverse health-promoting properties. However, concerns have recently emerged regarding the potential hepatotoxicity of some TCM compounds [1,2]. Emodin, a natural anthraquinone polyphenol found predominantly in herbs such as Rhubarb, Polygonum multiflorum, and Polygonum cuspidatum, is one such compound [3]. It has been widely used in TCM for its purgative, anti-inflammatory, and anticancer properties [[4], [5], [6]]. Nevertheless, evidence indicates that emodin and emodin-containing herbal preparations may induce hepatotoxicity in both humans and experimental animals, particularly when administered at high doses or over prolonged periods [[7], [8], [9]]. These findings highlight the urgent need to elucidate the mechanisms of emodin-induced hepatotoxicity.

Drugs undergo alterations in polarity and biological activity following metabolic transformation. Metabolic enzymes catalyze the biotransformation of drugs and are therefore particularly necessary for the detoxification or the generation of reactive metabolites from toxic compounds. Thus, understanding the metabolism of drugs such as emodin is crucial for elucidating their toxicity profiles. Previous studies have shown that emodin undergoes oxidation mediated by cytochrome P450 enzymes (CYPs) and glucuronidation mediated by UDP-Glucuronosyltransferases (UGTs) [10,11]. Our prior research has demonstrated that UGT2B7-mediated glucuronidation can attenuate emodin-induced hepatotoxicity [12]. Additionally, studies have indicated that emodin is extensively biotransformed into several hydroxylation metabolites, including 2-, 4-, 5-, 7-, and ω-hydroxyemodin, via CYPs in liver [8,13]. However, there is relatively little information available regarding the role of oxidation in toxicity of emodin. This study therefore aimed to elucidate the role of oxidation in emodin-induced hepatotoxicity.

In recent years, the integration of multi-omics approaches with systems biology has enabled comprehensive analysis of diverse omics datasets, thereby facilitating the identification of biomarkers, therapeutic targets and toxicological mechanism. For example, Zhao et al. identified acylcarnitines as potential biomarkers for the early detection of triptolide-induced liver injury through integrated transcriptomic and metabolomic analyses [14]. Similarly, Yue et al. identified 511 differentially expressed genes (DEGs) and 78 altered metabolites using transcriptomic and metabolomic analyses, revealing that lipid metabolism and arachidonic acid metabolism may serve as potential therapeutic targets for heroin-induced hepatotoxicity [15]. A recent study demonstrated that Rhododendron molle Flos-induced hepatotoxicity may result from oxidative stress leading to disruptions in steroid hormone biosynthesis, pyruvate metabolism, fatty acid biosynthesis, and arachidonic acid metabolism, as uncovered via bioinformatics and multi-omics integration [16]. These findings indicate that integrated omics could be a powerful tool to explore the potential mechanism of emodin-induced hepatotoxicity.

In the present study, the primary metabolic enzymes and related metabolites of emodin were systematically investigated using recombinant CYP enzymes. The toxicological profiles of hydroxylated metabolites derived from emodin were then comprehensively assessed using a series of in vitro models. To further validate these findings, in vivo experiments were conducted in murine models. Furthermore, the underlying molecular mechanisms contributing to emodin-induced hepatotoxicity were elucidated via integrated transcriptomic and metabolomic analyses. Taken together, this study not only reveals the metabolic detoxification pathways of emodin but also clarifies its toxicological mechanisms, providing a solid foundation for its rational clinical application.