United States Department of Agriculture, Agricultural Research Service, Natural Products Utilization Research Unit, P.O. Box 8048, University, MS 38677, USA.
J Chem Ecol. 2013 Feb;39(2):262-70. doi: 10.1007/s10886-013-0237-8. Epub 2013 Jan 13.
Leptospermone is a natural β-triketone that specifically inhibits the enzyme p-hydrophyphenylpyruvate dioxygenase, the same molecular target site as that of the commercial herbicide mesotrione. The β-triketone-rich essential oil of Leptospermum scoparium has both preemergence and postemergence herbicidal activity, resulting in bleaching of treated plants and dramatic growth reduction. Radiolabeled leptospermone was synthesized to investigate the in planta mechanism of action of this natural herbicide. Approximately 50 % of the absorbed leptospermone was translocated to the foliage suggesting rapid acropetal movement of the molecule. On the other hand, very little leptospermone was translocated away from the point of application on the foliage, indicating poor phloem mobility. These observations are consistent with the physico-chemical properties of leptospermone, such as its experimentally measured logP and pK a values, and molecular mass, number of hydrogen donors and acceptors, and number of rotatable bonds. Consequently, leptospermone is taken up readily by roots and translocated to reach its molecular target site. This provides additional evidence that the anecdotal observation of allelopathic suppression of plant growth under β-triketone-producing species may be due to the release of these phytotoxins in soils.
勒托斯permone 是一种天然的β-三酮，它专门抑制酶 p-羟苯基丙酮酸双加氧酶，这是与商业除草剂麦草畏相同的分子靶标位点。Leptospermum scoparium 的富含β-三酮的精油具有芽前和芽后除草活性，导致处理过的植物白化和明显的生长减少。合成了放射性标记的勒托斯permone，以研究这种天然除草剂在植物体内的作用机制。大约 50%的吸收的勒托斯permone 被转运到叶子中，这表明该分子的快速向顶运动。另一方面，很少有勒托斯permone 从叶子上的施药点转运出去，这表明韧皮部的移动性很差。这些观察结果与勒托斯permone 的物理化学性质一致，例如其实测的 logP 和 pK a 值、分子量、氢供体和受体的数量以及旋转键的数量。因此，勒托斯permone 很容易被根系吸收并转运到其分子靶标位点。这进一步证明了在产生β-三酮的物种下植物生长受到化感抑制的传闻观察可能是由于这些植物毒素在土壤中的释放。
