Killeen Daniel P, Larsen Lesley, Dayan Franck E, Gordon Keith C, Perry Nigel B, van Klink John W
Natural Products Utilization Research Unit, Agricultural Research Service, U.S. Department of Agriculture , University, Mississippi 38677, United States.
J Nat Prod. 2016 Mar 25;79(3):564-9. doi: 10.1021/acs.jnatprod.5b00968. Epub 2016 Jan 5.
Four trimethylated acylphloroglucinols (5-8) have been isolated from ma̅nuka (Leptospermum scoparium) foliage. Apart from myrigalone A (8), which has previously been isolated from European bog myrtle (Myrica gale), these compounds have not been characterized before. The nortriketones are structurally similar to the bioactive tetramethylated β-triketones from ma̅nuka, but have one less ring methyl group. Two oxidized trimethylated compounds, 9 and 10, were also isolated, but these are likely isolation artifacts. When evaluated for antibacterial activity against Gram-positive bacteria, myrigalone A (8) was slightly less potent (MIC 64 μg/mL) than the corresponding tetramethylated compound, grandiflorone (4) (MIC 16-32 μg/mL). Unlike their tetramethylated analogues, the nortriketones were inactive against the herbicide target enzyme p-hydroxyphenylpyruvate dioxygenase. The Raman spectra of leaf oil glands in different ma̅nuka varieties can be used to distinguish plants that contain nortriketones from those that accumulate triketones.
已从麦卢卡（Leptospermum scoparium）树叶中分离出四种三甲基化酰基间苯三酚（5 - 8）。除了之前已从欧洲香杨梅（Myrica gale）中分离出的桃金娘酮A（8）外，这些化合物此前尚未被鉴定。去甲三酮在结构上与来自麦卢卡的具有生物活性的四甲基化β - 三酮相似，但少一个环甲基。还分离出了两种氧化的三甲基化化合物9和10，但这些可能是分离过程中的产物。在针对革兰氏阳性菌的抗菌活性评估中，桃金娘酮A（8）的效力（MIC 64 μg/mL）略低于相应的四甲基化化合物大花酮（4）（MIC 16 - 32 μg/mL）。与它们的四甲基化类似物不同，去甲三酮对除草剂靶标酶对羟基苯丙酮酸双加氧酶无活性。不同麦卢卡品种叶片油腺的拉曼光谱可用于区分含有去甲三酮的植物和积累三酮的植物。
