Novel chiral borneol derivatives as potential cardioprotective agents: Design, synthesis and biological evaluation

The thalidomide incident has aroused our attention immensely to the structure activity relationship of chiral drugs. BO (Bing-Pian or Long-Nao) ccould be obtained from natural extracts or artificial synthesis. It has four different stereoisomers: (+)-isoborneol, (-)-isoborneol, (+)-borneol, and (-)-borneol. Due to the difference in activity, (+)-borneol and (-)-borneol had different clinical applications in China, Russia, India, and Southeast Asian countries. Nonetheless, borneol showed shortcomings of poor activity and certain toxicity. Herein, we designed and synthesized 36 diastereoisomeric borneol ester derivatives to develop cardioprotective agents with low toxicity and efficacy. The results of in vitro experiments indicated that most of the compounds could protect H9c2 cells against OGD/R injury. Among them, compound 19 revealed the strongest cardioprotective activity (87.5 ± 0.3 %, 10 μM) and anti-inflammatory activity (IC₅₀ = 13.49 ± 1.23 μM), which could significantly alleviate LDH leakage, inhibit ROS accumulation. Compound 19 was obtained by esterification reaction of (+)-borneol and 2,3,4-trimethoxy cinnamic acid. It has the same 2,3,4-trimethoxybenzene structure as the first-line anti-myocardial ischemia drug, trimetazidine. In addition, Integrated with network pharmacology, molecular docking and molecular dynamics simulation, caspase-1 stably combined to compound 19 and selected as the most effective therapeutic target. The chiral difference promoted the strong π-π conjugation of cinnamic acid fragment in compound 19 and caspase-1, which made the activity stronger. Western Blot results verified that compound 19 block pyroptosis by inhibiting the caspase-1/GSDMD/IL-18 signaling pathway. Furthermore, in vivo results showed that compound 19 could obviously reduce myocardial infarct size, prevent excessive release of cTn1, inhibit oxidative stress injury and improve cardiac ultrastructure in MI/R rats. The present study provided new potential myocardial protectant from borneol derivatives for clinical treatment of MI/R injury.