Design, Synthesis And Biological Activity Studies Of The Novel Stilbene Derivatives Containing Ligustrazinyl Group

Cerebrocardiac Vascular Disease(CVD) is the common disease that seriously threatens peoples' health and more than half of the death are caused by CVD. World Health Organization (WHO) claims CVD is 'The Top Enemy threatening the World Health'. Therefore, the research and development of cerebrocardiac vascular drugs are the one of important strategies for the medical therapy in the world.Ligustrazine(Lig; tetramethylpyrazine, TMP) is one major efficient component from Chinese traditional medicine herb Chuanxiong(Ligusticum wallichii Franchat), which is currently widely used in China as a new kind of calcium channel antagonists for the treatment of coronary atherosclerotic cardiovascular disease and ischemic cerebrocardiac vascular disease. Ligustrazine has been reported to inhibit the platelet aggregation, to cause negative chronotropic and inotropic responses on isolated atria, to inhibit vasoconstriction in isolated vascular strips, and to act as a vasodilator, a free radical scavenger, anti-thrombosis and anti-hypertention agent.However, Pharmacokinetics studies found that Ligustrazine presented low bioavailability and to be metabolized fast in vivo with short half-life of T_1/2 =2.89h, so accumulated toxicity often appeared in the patients for keeping an effective plasma concentration by the frequent administration. Structure-activity relationship studies indicated that pyrazine ring in the molecule of Ligustrazine might largely be the determinant of its pharmacodynamics, while the substituted groups might primarily govern its Pharmacokinetics and toxicity. Therefore, it is necessary to develop new generation of the cerebrocardiac vascular drugs from molecular modification of Ligustrazine.Resveratrol, one kind of stilbenes. has been reported to have the cerebrocardiac vascular activities of anti-platelet aggregation, anti-atherosclerosis, and to act as a vasodilator, a free radical scavenger and an antioxidant. The bioactivities of trans-resveratrol are usually better than those of cis-resveratrol.Holding the basic skeleton of the resveratrol as the structure model, the phenyl group was replaced by the ligustrazinyl group, which formed the novel Ligustrazine typed stilbene derivatives (A). In order to research the further structure-activity relationship of Ligustrazine derivatives, some prodrugs bearing drug-like groups or pharmacophores were also designed to produce ligustrazinyl heterocycle derivatives (B), for acquiring the pharmacologically additive or synergetic effects to improve pharmacokinetic properties. Totally, 37 compounds were synthesized, in which, 28 are Ligustrazine typed stilbene derivatives(A), 9 are ligustrazinyl heterocycle derivatives (B).In the synthesis, the Ligustrazine derivatives were prepared starting from Ligustrazine hydrochloride. The intermediates 2-hydroxymethyl-3,5,6-trimethylpyra-zine (4) and 2-chloromethyl-3,5,6-trimethylpyrazine (5) were prepared according to our previous work. The intermediate 3,5,6-trimethylpyrazine-2- carbaldehyde(6) was synthesizd through the Pfitzner-Moffatt oxidation. The intermediate 5 or 6 was converted to stilbene derivatives(A) by Wittig-Horner reaction, while 5 was alkylated to heterocycles to give the ligustrazinyl substituted heterocycles (B). All the newly synthesized compounds have not been reported in literature, and their chemical structures were confirmed by IR, NMR and ESI-MS.Endothelial cells play a critical physiological role in maintaining normal vessel and organ function. Oxidative stress is a cardiovascular risk factor and contributes significantly to endothelial injury. Therefore, the protection of endothelial cells against damage caused by oxidative stress is a very important therapeutic strategy. Stilbene derivatives containing ligustrazinyl group A1-A28 have been tested for protecting vascular endothelial cells (ECV-304) against hyperoxic acute injury. The viability of injured endothelial cells is assessed by methyl thiazolyl tetrazolium (MTT) assay. The biological results obtained from our experiments have demonstrated that compounds A6, A9 and All present excellent cerebrocardiac vascular activities, with high proliferation rates (>90%) for the injured cells at the concentration range of 0.05-0.10mmol.L^-1 and low EC₅₀ values of 0.03mmol.L^-1 0.09mmol.L^-1, 0.06mmol.L^-1 respectively. They are more potent than Ligustrazine (EC5o=0.79mmol.L^-1), while compounds A15, A24 and A28, lesss potent than A6, A9 and All, also have better activities (EC5o<0.30mmol.L^-1) than Ligustrazine. The other cerebrocardiac vascular activities screening tests of stilbene derivatives containing ligustrazinyl group (A) and ligustrazinyl heterocycle derivatives(B) are under way.In conclusion, 2 series of novel Ligustrazine typed stilbene derivatives (A) and ligustrazinyl substituted heterocycles (B) have been designed and synthesized. Some compounds are found to have better cerebrocardiac vascular activities than Ligustrazine. The biological results have demonstrated that compounds A6, A9 and All are promising lead compounds for developing new generation of the ligustrazine typed cerebrocardiac vascular drugs.