Eupatorium adenophorum is widely distributed throughout the world’s tropical and temperate regions. It has become a harmful weed of crops and natural environments. Its leaves contain bioactive compounds such as chlorogenic acid and may be used as feed additives. In this study, chlorogenic acid was extracted and separated from leaves of E. adenophorum. Three chlorogenic acid products were prepared with different purities of 6.11%, 22.17%, and 96.03%. Phytochemical analysis demonstrated that the main toxins of sesquiterpenes were almost completely removed in sample preparation procedure. The three products were evaluated for safety via in vitro and in vivo toxicological studies. All the products exhibited no cytotoxic effects at a dose of 400 μg/mL in an in vitro cell viability assay. When administered in vivo at a single dose up to 1.5 g/kg bw, all three products caused no signs or symptoms of toxicity in mice. These results encourage further exploration of extracts from E. adenophorum in feed additive application.

Molecular hydrogen (H ₂ ) has emerged as a promising bioactive gas with well-documented antioxidant, anti-inflammatory, and cytoprotective properties, and its therapeutic potential for a range of human diseases has been increasingly recognized. Accumulating evidence suggests that the gut microbiota (GM) may contribute to some of the biological effects of H ₂ . The GM serves as both a key site for endogenous H ₂ production and consumption, and a potential site of interaction with exogenous H ₂ supplementation, with possible implications for intestinal microecological homeostasis. This narrative review critically summarizes current evidence on the bidirectional relationship between H ₂ and the GM, focusing on microbial H ₂ production and consumption, the potential role of H ₂ in maintaining gut microbial homeostasis, and the impact of exogenous H ₂ supplementation on intestinal microecology. The potential therapeutic relevance of H ₂ -associated GM modulation is further discussed in metabolic diseases, gastrointestinal disorders, and neurodegenerative diseases. Proposed mechanisms include regulation of microbial composition, reinforcement of intestinal barrier integrity, suppression of inflammation and oxidative stress, modulation of microbial metabolites, and gut-organ axis signaling. Collectively, current evidence supports that H ₂ may influence the GM ecosystem. However, most supporting data remains preclinical, and whether GM alterations causally mediate the biological or therapeutic effects of H ₂ remains to be established. Elucidating the reciprocal interaction between H ₂ and the GM may provide new mechanistic insight into H ₂ -based interventions and facilitate the development of microbiota-targeted therapeutic strategies for human diseases.