中药黄芩中4种黄酮类化合物的密度泛函理论研究

Density Functional Theory Investigation of Four Flavanoids in the Scutellaria Baicalensis Georgi

采用DFT B3LYP方法在6-311G(d)基组下优化计算了黄芩苷、黄芩素、汉黄芩苷和汉黄芩素,分别从自然电荷分布、酚羟基的解离焓及前线轨道等方面分析了它们的活性.结果表明;4个分子C5处酚羟基氢原子上的正电荷数都是最大的,所带正电荷顺序是:黄芩苷>黄芩素>汉黄芩素>汉黄芩苷;酚羟基的解离能分析得到抗氧化活性顺序与其相同;最高占据轨道和最低空轨道的能级差ΔE的顺序是:黄芩苷<汉黄芩苷<黄芩素<汉黄芩素.黄芩苷消除.OH自由基的过渡态计算得到的活化能是113.2kJ.mol-1,反应热为-1 053kJ.mol-1.各种计算数据都表明黄芩苷在这四种黄酮化合物中的活性最大,消除自由基的理论活性顺序与文献报道的顺序一致.

Baicalin,Baicalein,Wogonoside and Wogonin,which are four main components of Scutellaria baicalensis Georgi,were calcaulated using the Density Functional Theory（DFT） B3LYP method with 6-311G（d） basis set.Their activities were analyzed based on natural charge population,BDE and the frontier orbitals.The result showed that the hydrogen atom of phenolic hydroxyl at C5 possessed the largest positive charge in all the four molecules.The charge on the hydrogen atom decreased along the series： Baicalin＆gt;Baicalein＆gt;Wogonin＆gt;Wogonoside.The BDE of phenolic hydroxyl at C5 showed the activity series： Baicalin＆gt;Baicalein＆gt;Wogonin＆gt;Wogonoside.The energy gap between HOMO and LUMO increased along the series： Baicalin＆lt;Wogonoside＆lt;Baicalein＆lt;Wogonin.When C6 phenolic hydroxyl on Baicalin scavenging ·OH,the computed result showed the activation energy was 113.2 kJ·mol-1 and the ΔH was-1 053 kJ·mol-1.All the parameters obtained showed that Baicalin has the highest activity in the four flavanoids.The theoretical result was consistent with the activity order in reported literatures.