黄芩苷的晶体结构研究

Crystal Structure of Baicalin

用乙醇-水溶液体系从黄芩中提取黄芩苷,纯化得黄芩苷纯度为95.2%.在步长0.0167°,停留时间7.62ms条件下对其粉末进行扫描,获得较高质量粉末衍射谱图.在运用密度泛函方法获得其分子低能量构象基础上,采用直接空间搜索法解析其晶体结构,得该样品属于单斜晶系,P21空间群,晶胞参数为:a=13.02,b=17.22,c=4.49,α=γ=90°,β=95.40°,Z=2,V=1016.13.结合自然键轨道理论分析,表明结构中苷元部分杂环可能具有芳香性.红外振动光谱结果发现,共轭效应导致了羰基伸缩振动频率红移,氢键的存在导致了羟基伸缩振动频率红移.由分子间氢键的影响,预测了其晶体生长特性.

Baicalin extracted from scutellaria by ethanol-water system was purified to 95.2%. Optimum resolution data of X-ray powder diffraction for the polycrystal powder were collected from an X＇Pert Pro MRD diffractometer with scanning conditions of 0.0167° and 7.62 ms per step. On basis of its molecular structure in low energy conformation by density functional theory, the crystal structure was determined by a direct-space approach. The results show that the crystal structure of baicalin belongs to monoclinic, P2 1 space group with unit cell parameters： a= 13.02 A, b= 17.22 A, c=4.49 A, α=γ=90°, β=95.40°, Z=2, V= 1016.1 A^3. Natural bond orbital （NBO） theory analysis of the structure indicates that the heterocyclic ring in the aglycone could be an aromatic ring. The IR result shows that conjugative effect is the reason for the red shift of stretching vibration frequency for carbonyl, meanwhile hydrogen bonds lead to the red shift of stretching vibration frequency for hydroxy groups. The crystal growth characteristic of baicalin was also forecasted by the help of H-bond analysis.