ABSTRACT
On-line attenuated total reflection infrared spectroscopy (ATR-IR) was used to gain a good understanding of the kinetics and mechanism for methyl cyclopentenone (MCP) synthesis from 2-methylfuran and formaldehyde in a four-step reaction. Combining in situ IR monitoring and a quantitative univariate model, the mechanisms for the main side reactions were discussed in depth. The presence and forming mechanism of the side product generated in step 1 (Mannich reaction) were reported for the first time. Off-line 1H NMR and GC-MS were used as reference tools to further clarify the structure of the side product. Results also show that an undesirable side reaction will take place if the reaction time for step 2 is longer than 3 h. Possible mechanisms for side reactions and optimized experimental conditions were suggested for the purpose of improving the selectivity of the main reaction to efficiently facilitate the yield of MCP. The present study demonstrates that on-line ATR-IR can be a powerful tool to gain insight into the process understanding of various chemical reactions, providing a solid theoretical foundation for highly efficient, large-scale synthesis of MCP.
ABSTRACT
Endothelial dysfunction and reduced nitric oxide (NO) signaling are a key element of the pathophysiology of nonalcoholic steatohepatitis (NASH). Stimulators of soluble guanylate cyclase (sGC) enhance NO signaling; have been shown preclinically to reduce inflammation, fibrosis, and steatosis; and thus have been proposed as potential therapies for NASH and fibrotic liver diseases. Praliciguat, an oral sGC stimulator with extensive distribution to the liver, was used to explore the role of this signaling pathway in NASH. We found that sGC is expressed in hepatic stellate cells and stellate-derived myofibroblasts, but not in hepatocytes. Praliciguat acted directly on isolated hepatic stellate cells to inhibit fibrotic and inflammatory signaling potentially through regulation of AMPK and SMAD7. Using in vivo microdialysis, we demonstrated stimulation of the NO-sGC pathway by praliciguat in both healthy and fibrotic livers. In preclinical models of NASH, praliciguat treatment was associated with lower levels of liver fibrosis and lower expression of fibrotic and inflammatory biomarkers. Praliciguat treatment lowered hepatic steatosis and plasma cholesterol levels. The antiinflammatory and antifibrotic effects of praliciguat were recapitulated in human microtissues in vitro. These data provide a plausible cellular basis for the mechanism of action of sGC stimulators and suggest the potential therapeutic utility of praliciguat in the treatment of NASH.
