Graduate School of Biotechnology, Kyung Hee University, Giheung, Yongin-si, Gyeonggi-do 1732, Republic of Korea.
J Med Microbiol. 2020 May;69(5):689-696. doi: 10.1099/jmm.0.001196. Epub 2020 May 4.
Rhein (4, 5-dihydroxyanthraquinone-2-carboxylic acid) has various properties, including anti-inflammatory, antioxidant and anticancer activities. However, the mechanism underlying the role of rhein in antimicrobial activity remains largely unknown. This study aims to identify potential natural compounds of rhein that are capable of inhibiting and elucidate the effects of rhein on NADH dehydrogenase-2 activity in . The anti activity of compounds was analysed using minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), the paper disc diffusion test and the checkerboard dilution test. To check whether rhein was inhibitory, putative type II NADH dehydrogenase (NDH-2) of was analysed, cloned and expressed in and then NDH-2 purification was assessed with Ni-NTA before rhein inhibition of NADH dehydrogenase-2 activity was checked with ferricyanide [KFe(CN)] as a substrate. The results showed that the MIC of rhein against was 6.25 µg ml, while the MBC was 12.5 µg ml, and there was a 38 mm inhibition zone in the paper disc diffusion test. Rhein showed an additive two- to fourfold reduction of the MIC value with four antibiotics on the checkerboard dilution test. The purified NADH dehydrogenase gene product showed a size of approximately 51 kDa and had a of 23 µmol and a of 280 µm. The inhibitory effect of rhein against NADH dehydrogenase-2 activity was non-competitive with ferricyanide [KFe(CN)] with a value of 3.5-4.5 µm. This study provided evidence of the inhibitory effects of rhein on the growth of by blocking of NADH dehydrogenase-2 activity. This mechanism of inhibitory activity in the reduction of ROS formation and ATP productivity should be further tested in and the question of whether rhein inhibits the natural growth of should be investigated.
大黄酸（4,5-二羟基蒽醌-2-羧酸）具有多种特性，包括抗炎、抗氧化和抗癌活性。然而，大黄酸在抗菌活性中的作用机制在很大程度上尚不清楚。本研究旨在鉴定能够抑制的大黄酸的潜在天然化合物，并阐明大黄酸对 NADH 脱氢酶-2 活性的影响。采用最低抑菌浓度（MIC）、最低杀菌浓度（MBC）、纸片扩散试验和棋盘稀释试验分析化合物的抗菌活性。为了检查大黄酸是否具有抑制作用，分析了 的推定型 II NADH 脱氢酶（NDH-2），并在大肠杆菌中进行了克隆和表达，然后用 Ni-NTA 评估 NDH-2 纯化，并用铁氰化钾[KFe(CN)]作为底物检查大黄酸对 NADH 脱氢酶-2 活性的抑制作用。结果表明，大黄酸对 的 MIC 为 6.25μg/ml，MBC 为 12.5μg/ml，纸片扩散试验中有 38mm 的抑菌圈。棋盘稀释试验中，大黄酸与四种抗生素联合使用时，MIC 值降低了两到四倍。纯化的 NADH 脱氢酶基因产物的大小约为 51kDa，具有 23µmol 的 Km 和 280µm 的 Vmax。大黄酸对 NADH 脱氢酶-2 活性的抑制作用是非竞争性的，与铁氰化钾[KFe(CN)]的 Ki 值为 3.5-4.5µm。本研究为大黄酸通过阻断 NADH 脱氢酶-2 活性抑制生长提供了证据。这种抑制活性在降低 ROS 形成和 ATP 产生方面的机制应该在进一步在大肠杆菌中进行测试，并且应该研究大黄酸是否抑制大肠杆菌的自然生长。
