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Abstract：
Emodin was extracted from Rheum officinale Baill by ultrasound-assisted extraction (UAE), and ethanol was chosen as the suitable solvent through SEM and molecular dynamic simulation. Under the optimum conditions (power 541 W, time 23 min, liquid to material ratio 13:1 mL/g, ethanol concentration 83 %) predicted by RSM, the yield of emodin was 2.18 ± 0.11 mg/g. Moreover, ultrasound power and time displayed the significant effects on the extraction process. Extracting dynamics analysis indicated that the extraction process of emodin by UAE conformed to Fick\'s second diffusion law. The results of antibacterial experiments suggested that emodin can damage cell membrane and inhibit the expression of cps2A, sao, mrp, epf, neu and the hemolytic activity of S. suis. Biolayer interferometry and FT-IR multi-peak fitting assays demonstrated that emodin induced a secondary conformational shift in CcpA. Molecular docking and molecular dynamics confirmed that emodin bound to CcpA through hydrogen bonding (ALA248, GLU249, GLY129 and ASN196) and π-π T-shaped interaction (TYR225 and TYR130), and the mutation of amino acid residues affected the affinity of CcpA to emodin. Therefore, emodin inhibited the sugar utilization of S. suis through binding to CcpA, and CcpA may be a potential target to inhibit the growth of S. suis.
摘要：
通过超声辅助提取（UAE）从大黄中提取大黄素，通过SEM和分子动力学模拟选择乙醇作为合适的溶剂。在最佳条件下(功率541W，时间23分钟,液料比13:1mL/g,乙醇浓度83%)由RSM预测，大黄素的产量为2.18±0.11mg/g。此外，超声功率和时间对提取过程有显著影响。提取动力学分析表明,UAE提取大黄素的过程符合Fick第二扩散定律。抗菌实验结果提示大黄素能损伤细胞膜,抑制cps2A的表达,sao,mrp,epf,neu和猪链球菌的溶血活性。Biolayer干涉法和FT-IR多峰拟合分析表明，大黄素诱导了CpA的二次构象移位。分子对接和分子动力学证实大黄素通过氢键（ALA248，GLU249，GLY129和ASN196）和π-πT形相互作用（TYR225和TYR130）与CpA结合，氨基酸残基的突变影响了CpA对大黄素的亲和力。因此,大黄素通过与CpA结合抑制猪链球菌的糖利用，和CpA可能是抑制猪链球菌生长的潜在靶标。
