玫瑰茄醇提物的抑菌活性及其作用机制

Antibacterial Mechanism of Ethanolic Extract of Hibiscus sabdariffa Against Escherichia coli and Staphylococcus aureus

玫瑰茄具有多种药理活性,包括抗肿瘤、抗氧化和抑菌作用等,但目前关于玫瑰茄的抑菌作用研究较少,有关抑菌机制方面的研究尚未见报道.本文通过测定玫瑰茄醇提物对大肠杆菌和金黄色葡萄球菌细胞膜、蛋白质和核酸的影响,及其与DNA的作用方式等,系统阐述玫瑰茄的抑菌作用机制.电导率和大分子物质的测定结果显示,玫瑰茄醇提物只对菌体的细胞膜造成微小损伤,其抑菌作用的靶点不在细胞膜.SDS-PAGE和DAPI结果显示,玫瑰茄醇提物可抑制大肠杆菌和金黄色葡萄球菌蛋白质和核酸的合成.琼脂糖凝胶电泳和紫外吸收光谱结果显示,玫瑰茄醇提物可与DNA结合,当DNA与药物的浓度比较低时,玫瑰茄醇提物与DNA以嵌入结合为主,当二者的浓度较高时,两者间发生的是氢键结合.上述结果证明,玫瑰茄醇提物对大肠杆菌和金黄色葡萄球菌抑菌机制,主要是药物通过与DNA发生嵌入结合和氢键结合,使DNA不能进行正常的复制和转录,降低核酸的含量,进而影响蛋白质的合成,最终导致菌体生物学功能的丧失.

Hibiscus sabdariffa（ HS） has extensive physiological activities including anti-oxidant,antitumor and anti-bacterial activities. However,the anti-bacterial mechanisms were rarely reported. Here we investigated the effect of the ethanol extract HS on cell membrane integrity,protein and nucleic acid synthesis in Escherichia coli and Staphyloccocus aureus. We systematically investigated the anti-bacterial mechanism of the ethanol extract HS. Conductivity and macromolecular leakage results showed that the ethanol extract HS only slightly damaged the membrane of bacteria,which suggested that the antibacterial activity did not relate to the cell membrane. SDS-PAGE and DAPI staining results showed that the ethanol extract HS could potently inhibit the synthesis of proteins and nucleic acids. Agarose gel electrophoresis and the UV-visible spectrophotometric results indicated that the ethanol extract HS could integrate with DNA： at low concentration ratio of DNA and HS,the ethanol extract HS could insert into DNA double helix; while at high concentration ratio,the ethanol extract HS interacted with DNA through hydrogen bond. Our results indicated that the anti-bacterial mechanism of the ethanol extract HS was mainly through combining with DNA,which inhibited the transcription and the translation of DNA,andthus inhibited the biological function of bacteria.