Discovery Of Lead Compound Liguzinediol And Study Of Its Positive Inotropic Effect On Myocardium

Ligustrazine(tetramethylpyrazine) is an amines alkaloid monomer extracted from ligusticum.It is an active component of ligusticum which has various pharmacologic activities such as vasodilation,antiplatelet aggregation,preventing thrombosis,anti-free-radical action, improving cerebral ischemia,increasing coronary perfusion flow,reducing moisture capacity of myocardial,pretenting heart,and besides it can induce positive inotropic effect on myocardium. However,ligustrazine presented low bioavailability and short half-life in vivo because it could be oxidized into metabolins with high polarity and good water solubility and excreted easily in vitro by urine.So accumulated toxicity often appeared in the patients for keeping an effective plasma concentration by the frequent administration.Therefore,it is necessary to select some positive inotropic drugs with good water solubility and high bioavailability by molecular modification of ligustrazine.The research showed that 2,5-diacetoxymethyl-3,6-dimethylpyrazine and liguzinediol which has low toxicity and good water solubility could induce positive inotropic effect on myocardium with no arrhythmia risk. In conclusion,liguzinediol can be lead compoud for research and development of positive inotropic drugs.This thesis include six parts:1 Synthesis of ligustrazine derivativesN-O-tetramethyl-pyrazine,N,N'-dioxiotetramethylpyrazine,2,5-diacetoxy-methyl -3,6-dimethylpyrazine,2-hydroxymethyl-3,5,6-trimthylpyrazine,liguzinediol and 3,5,6-trimthylpyrazine-2-dimethylsuccinate were prepared from Ligustrazine.The structrues were comfimed by UV,IR,NMR and MS.2 Bioactive screening of ligustrazine derivativesInotropic actions of ligustrazine derivatives in normal isolated rat hearts were investigated by Langendorff technique.The results showed that liguzinediol and 2,5-diacetoxymethyl-3,6-dimethylpyrazine can induce positive inotropic effect on myocardium with no arrhythmia risk.However,2-hydroxymethyl-3,5,6-trimthylpyrazine had no effect in hearts but caused arrhythmia.3 Process optimization and scale-up experiment of liguzinediolThe process optimization of ligustrazine derivatives showed that the reaction temperature and reaction time to synthesize N,N'-dioxotetramethylpyrazine were 98℃and 12h,respectively.The reaction temperature and reaction time to synthesize 2,5-diacetoxymethyl-3,6-dimethylpyrazine were 100℃and 4h,respectively.Reaction temperature and time were major factors to the yields. 4 Pharmacodynamic study of liguzinediolThe effects of liguzinediol on cardiac contractile force and bloodpressure rat hearts were determined using a RM6240B/C four channel physiological recording instrument. Liguzinediol induced a significant increase of LVSP,+dp/dt_max,-dp/dt_max,SAP,MAP, MPP and a significant decrease in t-dp/dt_max,LVEDP.Liguzinediol produced a positive inotropic effect on normal rat hearts.5 Acute toxicity of liguzinediolLD50 of liguzinediol was determinated by administration of tail vein in mice. LD50 of female and male mice were 1.5921g/kg and 1.6922g/kg,respectively.6 Underlying mechanism of liguzinediolUnderlying mechanism of liguzinediol was elucidated by interfering withα,β,D₁, H₁ receptor antagonist and L-type Ca²⁺ channel inhibitor.Liguzinediol exerted its effect on enhancing contraction of isolated rat heart through activating L-type Ca²⁺ channel.