Detecting metabolites of different transition metallithospermate B complexes after intravenous injection in rats

Aim: Lithospermate B (LSB) isolated from the traditional Chinese medicine danshen ( Salvia miltiorrhiza ) is an effective Na + /K + -ATPase inhibitor and used to treat congestive heart failure. The inhibition of LSB on Na + /K + -ATPase is potentiated by forming complexes with transition metal ions. Here we investigated the safety and metabolites of different transition metal-LSB complexes in rats. Methods: LSB complexed with six different transition metal ions (Mg 2+ , Zn 2+ , Cr 3+ , Co 2+ , Ni 2+ and Mn 2+ ) were prepared. Adult male SD rats were injected with the different metal-LSB complexes (50 mg/kg, iv), and their bile and blood samples were collected. The metabolites of the metal-LSB complexes in the samples were analyzed using mass spectroscopy. Results: In rats injected with LSB complexed with Mg 2+ , Zn 2+ , Cr 3+ , Ni 2+ or Mn 2+ , LSB and its four putative metabolites were equivalently detected in their bile samples. Mn 2+ -LSB exhibited distinct metabolite profiles compared with the other four metal-LSB complexes. The four putative metabolites were identified as 3-monomethyl-LSB, 3,3′′-dimethyl-LSB, 3,3′′′-dimethyl-LSB and 3,3′′,3′′′-trimethyl-LSB. The tracking of successive bile samples of rats injected with Mg 2+ -LSB, Zn 2+ -LSB and Mn 2+ -LSB concurrently demonstrated that LSB was firstly methylated at position 3, then at position 3′′, and, finally, the 3′′′ hydroxyl group. All rats injected with Co 2+ -LSB died. Conclusion: Zn 2+ -LSB, Cr 3+ -LSB, Ni 2+ -LSB or Mn 2+ -LSB produces identical four methylated metabolites of LSB in rats, and seemed to be as safe as LSB or Mg 2+ -LSB.