Department of Biology, University of Florence, Via Madonna del Piano 6, 50019, Sesto Fiorentino, Italy.
Department of Experimental and Clinical Medicine, University of Florence, Largo Brambilla 3, 50134, Florence, Italy.
Sci Rep. 2019 Jul 26;9(1):10897. doi: 10.1038/s41598-019-47329-8.
The controversial anti-proliferative effects of Echinacea purpurea (L.) Moench (Asteraceae) might be related to different plant metabolites contained in plant samples, extracts and products. The influence of bacterial endophytes on the synthesis of bioactive compounds in the medicinal plants has been previously demonstrated but there are only few studies addressing anticancer effects and mechanisms of E. purpurea extracts following endophytic colonization. The present study aimed to test and compare the lactate dehydrogenase (LDH) inhibition potential of n-hexane and methanol extracts from in vitro endophyte non-inoculated and inoculated E. purpurea plants. An in vitro model was previously set up to perform the infection of axenic E. purpurea plants with bacterial endophytic strains isolated from E. purpurea aerial part. Only methanol extracts showed LDH5 inhibition, in particular the richest in chicoric acid and most strongly inhibiting extract was obtained from inoculated stem and leaves of E. purpurea (IC = 0.9 mg/ml). Chicoric acid showed an IC value (66.7 µM) in enzymatic assays better than that of the reference compound galloflavin. Modeling studies were carried out to suggest the putative interaction mode of chicoric acid in the enzyme active site. This in vitro model on plant-bacterial interaction may lead to obtain extracts from plants enriched in bioactive compounds and it is a new approach for the discovery of novel anticancer compounds.
紫锥菊（Echinacea purpurea（L.）Moench）（菊科）有争议的抗增殖作用可能与植物样品、提取物和产品中含有的不同植物代谢物有关。先前已经证明了细菌内生菌对药用植物中生物活性化合物合成的影响，但只有少数研究涉及内生菌定植后紫锥菊提取物的抗癌作用和机制。本研究旨在测试和比较来自体外非接种和接种内生菌的紫锥菊植物的正己烷和甲醇提取物的乳酸脱氢酶（LDH）抑制潜力。先前建立了一个体外模型，用于用从紫锥菊地上部分分离的细菌内生菌株感染无菌紫锥菊植物。只有甲醇提取物显示 LDH5 抑制作用，特别是从接种的紫锥菊茎和叶中获得的富含 chicoric 酸和抑制作用最强的提取物（IC=0.9mg/ml）。在酶促测定中，chicoric 酸的 IC 值（66.7µM）优于参考化合物 galloflavin。进行了建模研究以提出 chicoric 酸在酶活性位点中的假定相互作用模式。这种植物-细菌相互作用的体外模型可能会获得富含生物活性化合物的植物提取物，这是发现新型抗癌化合物的新方法。
