Department of Biochemistry and Chemistry, Fort Lewis College, 1000 Rim Dr., Durango, CO 81301, USA.
Department of Biology, Fort Lewis College, 1000 Rim Dr., Durango, CO 81301, USA.
Biomolecules. 2019 Jul 27;9(8):312. doi: 10.3390/biom9080312.
American Foulbrood (AFB) is a deadly bacterial disease affecting pupal and larval honey bees. AFB is caused by the endospore-forming bacterium (PL). Propolis, which contains a variety of organic compounds, is a product of bee foraging and is a resinous substance derived from botanical substances found primarily in trees. Several compounds from the class of caffeic acid esters, which are commonly found in propolis, have been shown to have antibacterial activity against PL. In this study, six different caffeic acid esters were synthesized, purified, spectroscopically analyzed, and tested for their activity against PL to determine the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs). Caffeic acid isopropenyl ester (CAIE), caffeic acid benzyl ester (CABE), and caffeic acid phenethyl ester (CAPE) were the most effective in inhibiting PL growth and killing PL cell with MICs and MBCs of 125 µg/mL when used individually, and a MIC and MBC of 31.25 µg/mL for each compound alone when CAIE, CABE, and CAPE are used in combination against PL. These compounds inhibited bacterial growth through a bactericidal effect, which revealed cell killing but no lysis of PL cells after 18 h. Incubation with CAIE, CABE, and CAPE at their MICs significantly increased reactive oxygen species levels and significantly changed glutathione levels within PL cells. Caffeic acid esters are potent bactericidal compounds against PL and eliminate bacterial growth through an oxidative stress mechanism.
美洲幼虫腐臭病（AFB）是一种致命的细菌性疾病，影响蛹和幼虫蜜蜂。AFB 是由芽孢形成细菌（PL）引起的。蜂胶含有多种有机化合物，是蜜蜂觅食的产物，是一种树脂状物质，主要来源于植物物质，发现于树木中。几种来源于咖啡酸酯类的化合物，在蜂胶中很常见，已被证明对 PL 具有抗菌活性。在这项研究中，合成、纯化、光谱分析了六种不同的咖啡酸酯，并测试了它们对 PL 的活性，以确定最小抑菌浓度（MIC）和最小杀菌浓度（MBC）。咖啡酸异丙烯酯（CAIE）、咖啡酸苄酯（CABE）和咖啡酸苯乙酯（CAPE）在单独使用时对 PL 生长的抑制和杀灭作用最有效，MIC 和 MBC 分别为 125 µg/mL；当 CAIE、CABE 和 CAPE 单独使用时，每种化合物的 MIC 和 MBC 分别为 31.25 µg/mL。这些化合物通过杀菌作用抑制细菌生长，在 18 小时后显示出细胞杀伤作用，但没有 PL 细胞的裂解。在 MIC 下孵育 CAIE、CABE 和 CAPE 显著增加了 PL 细胞内活性氧水平，并显著改变了谷胱甘肽水平。咖啡酸酯是针对 PL 的强效杀菌化合物，通过氧化应激机制消除细菌生长。
