Discovery and synthesis of novel glyrrhizin-analogs containing furanoylpiperazine and the activity against myocardial injury in sepsis

The signaling pathway mediated by high mobility group protein B1 (HMGB1) plays a key role in myocardial injury during sepsis. Glyrrhizin (GL) is a natural product that inhibits HMGB1 biological activities through forming GL-HMGB1 complex; the research shows its aglycone (GA) is the main pharmacophore binding to HMGB1, while the glycosyl mainly altering its pharmacokinetic properties and enhances the stability of the complex. GL is often metabolized to GA in the gastrointestinal tract, which has a lower efficacy in the treatment of HMGB1-mediated diseases. To obtain the GL analogs with higher activity and better pharmacokinetic properties, 24 GL analogs were synthesized by simplification the glycosyl of GL. Among all the compounds, compound 11 with furanoylpiperazine was screened. The pharmacokinetics experiments showed that compound 11 is converted to 11a in vivo, and 11 serves as its prodrug. Compound 11a displayed a lower cytotoxicity to RAW264.7 cells and three types of cardiomyocyte lines, with IC₅₀ > 800 µM. In the anti-inflammatory assay, 11a not only strongly inhibited NO production (IC₅₀ 5.73 µM), but also down-regulated the levels of HMGB1, IL-1β and TNF-α in a dose-dependent manner; in the anti-oxidative stress assay, compound 11a reduced the level of ROS and increased the MMP in H9c2 cells. More importantly, in the myocardial injury model of septic mice, compound 11a not only alleviated the symptom of myocardial injury by reducing inflammatory infiltration and oxidative stress, but also improved the myocardial blood supply by shrinking the inner diameter of the left ventricle and increasing the ejection fraction (EF) more dramatically (155.8 %); meanwhile, compound 11a adjusted myocardial enzymes in serum of septic mice. In addition, in molecular docking experiments, compound 11a showed stronger HMGB1 binding ability than GL. In summary, compound 11 is a prodrug, which can be converted to 11a in vivo. And compound 11a has a good activity against septic myocardial injury, as well as improving the myocardial blood supply function. This suggests compound 11 is a potential drug candidate for the treatment of septic myocardial injury and deserves further investigate.