Toxic metabolites and metabolic soft spots of celastrol based on glutathione metabolic capture and high-resolution mass spectrometry

Background Celastrol is known as one of the most medicinally valuable compounds. However, the pharmaceutical application of celastrol is significantly limited due to high toxicity, while there are few reports on the mechanism of toxicity.Methods This study searched for possible toxic metabolites through phase I in vitro metabolism and glutathione capture experiments. Then in vivo metabolism experiments in mice and rats were conducted to look for metabolites in vivo. Finally, mice in vivo toxicity experiment was conducted to verify the toxicity of different doses of celastrol to mice.Results In the in vivo and in vitro metabolism experiments, we found 7 phase I metabolites in vitro, 9 glutathione conjugation metabolites in vitro, and 20 metabolites in vivo. The metabolic soft points of celastrol could be the quinone methyl structure at C3-OH and C6. In vivo toxicity experiments show that celastrol causes weight loss, diarrhea, gastrointestinal tract and liver inflammation in mice.Conclusions This study analyzed the metabolites and possible metabolic soft spots of celastrol, and its hepatotoxicity and gastrointestinal toxicity were demonstrated through in vivo studies for the first time. The results might provide an important basis for potential structural modification to increase the druggability of celastrol.