Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University , Okayama 700-8530, Japan.
Department of Microbiology, Graduate School of Biomedical and Health Sciences, Hiroshima University , Hiroshima 734-8553, Japan.
J Nat Prod. 2017 Oct 27;80(10):2723-2733. doi: 10.1021/acs.jnatprod.7b00496. Epub 2017 Oct 11.
Three new ellagitannin oligomers, isorugosins H (1), I (2), and J (3), together with 11 known hydrolyzable tannins were isolated from an aqueous acetone extract of the fresh leaves of Liquidambar formosana. Their chemical structures were elucidated based on spectroscopic data and chemical conversion into known hydrolyzable tannins. The bridging mode of the valoneoyl groups between their sugar moieties has been identified only in this plant species. Additionally, the effects of the isorugosins isolated from this species on drug-resistant bacteria were evaluated and showed that isorugosin A (4) exhibited the most potent antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). The isorugosins also had a suppressing effect on pigment formation in Pseudomonas aeruginosa. The isorugosin-protein complexes were analyzed using size-exclusion chromatography and polyacrylamide gel electrophoresis to clarify the relationship of their antibacterial properties with their protein interaction potency as hydrolyzable tannins. The results suggested that the antibacterial properties of hydrolyzable tannins are not simply a result of their binding activity to proteins, but are due to other factors such as the accessibility of polyphenolic acyl groups to bacterial membranes.
从枫香树新鲜叶片的水丙酮提取物中分离得到三种新的鞣花单宁低聚物，即异鲁考辛 H（1）、I（2）和 J（3），以及 11 种已知的可水解单宁。根据光谱数据和化学转化为已知可水解单宁，确定了它们的化学结构。在这种植物中，仅鉴定出糖部分之间的瓦伦oyl 基团的桥接模式。此外，还评估了从该物种中分离出的异鲁考辛对耐药菌的影响，结果表明异鲁考辛 A（4）对耐甲氧西林金黄色葡萄球菌（MRSA）表现出最强的抗菌活性。异鲁考辛还对铜绿假单胞菌的色素形成具有抑制作用。通过凝胶排阻色谱和聚丙烯酰胺凝胶电泳分析异鲁考辛-蛋白复合物，以阐明其抗菌性质与其作为可水解单宁的蛋白相互作用强度之间的关系。结果表明，可水解单宁的抗菌性质不仅仅是其与蛋白质结合活性的结果，而是由于多酚酰基对细菌膜的可及性等其他因素。
