Okamura Shinya, Nishiyama Eri, Yamazaki Tomohiro, Otsuka Nao, Taniguchi Shoko, Ogawa Wakano, Hatano Tsutomu, Tsuchiya Tomofusa, Kuroda Teruo
Department of Microbiology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan.
Botanical Garden, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan.
Biochim Biophys Acta. 2015 Jun;1850(6):1245-52. doi: 10.1016/j.bbagen.2015.02.012. Epub 2015 Feb 27.
Multidrug-resistant bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin resistant enterococci (VRE), cause serious infections at clinical sites, for which the development of new drugs is necessary. We screened candidates for new antibiotics and investigated its action mechanism.
An antimicrobial compound was isolated from an extract of Nuphar japonicum. Its chemical structure was determined by NMR, MS, and optical rotation. We measured its minimum inhibitory concentration (MIC) using the microdilution method. The effects of the compound on DNA gyrase and DNA topoisomerase IV were investigated with DNA supercoiling, decatenation, and cleavage assay.
We isolated and identified 6,6'-dihydroxythiobinupharidine as the antimicrobial compound. The MIC of this compound was 1-4 μg/mL against various MRSA and VRE strains. We also demonstrated that this compound inhibited DNA topoisomerase IV (IC50 was 10-15 μM), but not DNA gyrase in S. aureus, both of which are known to be the targets of quinolone antibiotics and necessary for DNA replication. However, this compound only exhibited slight cross-resistance to norfloxacin-resistant S. aureus, which indicated that DTBN might inhibit other targets besides topoisomerase IV. These results suggest that 6,6'-dihydroxythiobinupharidine may be a potent candidate or seed for novel antibacterial agents.
DTBN from N. japonicum showed anti-MRSA and anti-VRE activities. DTBN might be involved in the inhibition of DNA topoisomerase IV.
DTBN might be useful as a seed compound. The information on the inhibition mechanism of DTBN will be useful for the modification of DTBN towards developing novel anti-MRSA and anti-VRE drug.
耐多药细菌，如耐甲氧西林金黄色葡萄球菌（MRSA）和耐万古霉素肠球菌（VRE），在临床部位引起严重感染，因此有必要开发新药。我们筛选了新型抗生素的候选物并研究了其作用机制。
从日本萍蓬草提取物中分离出一种抗菌化合物。通过核磁共振（NMR）、质谱（MS）和旋光测定法确定其化学结构。我们使用微量稀释法测量其最低抑菌浓度（MIC）。通过DNA超螺旋、解连环和切割试验研究该化合物对DNA回旋酶和DNA拓扑异构酶IV的影响。
我们分离并鉴定出6,6'-二羟基硫代萍蓬定作为抗菌化合物。该化合物对各种MRSA和VRE菌株的MIC为1-4μg/mL。我们还证明该化合物抑制金黄色葡萄球菌中的DNA拓扑异构酶IV（IC50为10-15μM），但不抑制DNA回旋酶，这两种酶都是喹诺酮类抗生素的已知靶点且对DNA复制是必需的。然而，该化合物仅对耐诺氟沙星金黄色葡萄球菌表现出轻微的交叉耐药性，这表明DTBN可能除了拓扑异构酶IV之外还抑制其他靶点。这些结果表明6,6'-二羟基硫代萍蓬定可能是新型抗菌剂的有力候选物或种子。
来自日本萍蓬草的DTBN表现出抗MRSA和抗VRE活性。DTBN可能参与对DNA拓扑异构酶IV的抑制。
DTBN可能作为一种种子化合物有用。关于DTBN抑制机制的信息将有助于对DTBN进行修饰以开发新型抗MRSA和抗VRE药物。
