Design, Synthesis And Anti-ischemia Activties Of Linarinic Acid Derivatives

Cerebrovascular disease (CVD) has severely threatened human health and life, particularly in situation of ischemic cerebrovascular disease (ICVD). Nowadays, there are still lack of safe and effective drugs to heal the neuronal damage and brain tissue damage caused by ischemia in clinic. Thus, it is extremely far from finished to develop the potent therapeutic drugs,through a thorough study of pathogenesis and rational drug target for the prevention and treatment of ischemic cerebrovascular disease.(-)-Linarinic acid (LA) is a novel chiral natural product and belongs to tricyclic quinazoline alkaloids, which was isolated from the medicinal herb L. vulgaris Mill by the department of Natural Medicinal Chemistry in Shenyang Pharmaceutical University. Linarinic acid may have various pharmacological properties, including neuroprotectants, nootropics, cerebral vasodilator and heart stimulants, according to the prediction results by PASS (Prediction of Activity Spectra for Substances). It could significantly extend the survival time of mices, and also reduced the MDA (malondialdehyde) content in liver and cerebra of aged rats with a significant dose-dependent in both in vitro and in vivo studies. The results of ischemia-induced cell injury in an in vitro oxygen glucose deprivation (OGD) model of ischemic stroke in SH-SY5Y cells showed that linarinic acid exhibited good neuroprotective effects in the three concentrations of 100 nM, 1?M and 10?M.Based on the above results, linarinic acid was selected as the lead compound for anti-cerebral ischemia activity and 78 tetrahydropyrrolo[2,1-b]quinazoline compounds were designed and synthesized according to the theories of bioisosterism, combination principles and partial modification etc. Such compounds include thiophenyl substituted at C-7 position of tetrahydropyrrolo [2,1 -b]quinazoline compounds, cyano, 1H-tetrazolyl, 1,2,4-triazinyl,carboxamide and acyloxy methylene substituted at C-1 position of tetrahydropyrrolo[2,1-b]quinazoline compounds, and benzylidene substituted at C-3 position of tetrahydropyrrolo[2,1-b]quinazoline compounds. In order to further study their structure-activity relationships (SAR) and get the novel anti-cerebral ischemia compounds, we synthesized 2 tetrahydro-6H-pyrido[2,1-b]quinazoline compounds. All the above compounds were identified by ESI-MS, 1H-NMR, specific rotation and melting point, part of them were confirmed by HRMS, 13C-NMR and IR. All of the synthesized compounds have not been reported in the literature.Forty linarinic acid derivatives were evaluated for their neuroprotective effects against oxygen glucose deprivation (OGD) model of ischemic stroke in SH-SY5Y cells, which were pretreated with 100 pM, 1 nM, 10 nM, 100 nM, 1?M and 10?M concentrations of test compounds, using linarinic acid and ShuXueTong as reference compounds. The result showed that most of the derivatives exhibited good protective effects on the damaged SH-SY5Y cells,and 4 compounds including TY-A-25, TY-A-29, TY-A-30 and TY-A-34 increased cell viability more than 90% at concentrations of 1 nM, 10 nM, 100 nM and 1?M, and the most potential compound TY-A-29 were even over 95%, which was superior to that of linarinic acid. At 3 concentrations of 100 nM, 1?M and 10?M, TY-A-03 and TY-A-31 significantly increased SH-SY5Y cell viability over 90%, showing good neuroprotective effects.These preliminary structure-activity relationships (SARs) suggested that, the introduction of a thiophenyl substituent at the C-7 position of linarinic acid had enhanced effect on the activity; cyano, 1H-tetrazolyl, 1,2,4-triazinyl and carboxamide substituted at C-1 position also exhibited good influence on protective activity; While benzylidene substituted at C-3 position of tetrahydropyrrolo [2,1-b]quinazoline compounds showed decreased cell viability compared to the above derivatives.With the discovery of new anti-cerebral ischemic drug as a target, the most potential natural products linarinic acid were selected as the lead compound, several classes of linarinic acid derivatives were designed and synthesized. The pharmacological results showed that some compounds exhibited promising anti-cerebral ischemia potency. Among them, compounds TY-A-03, TY-A-25, TY-A-29, TY-A-30, TY-A-31 and TY-A-34 displayed significant anti-cerebral ischemia activity, and so they warrant the pursuit of additional research. The primary structure-activity relationships of the compounds were investigated, which laid the foundation for further research.