Islam A K M Mominul, Ohno Osamu, Suenaga Kiyotake, Kato-Noguchi Hisashi
Department of Applied Biological Science, Faculty of Agriculture, Kagawa University, 2393 Ikenobe, Miki, Kagawa 761-0795, Japan.
Department of Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku, Yokohama 223-8522, Japan.
J Plant Physiol. 2014 Jul 1;171(11):877-83. doi: 10.1016/j.jplph.2014.03.003. Epub 2014 Mar 15.
Leucas aspera (Lamiaceae), an aromatic herbaceous plant, is well known for many medicinal properties and a number of bioactive compounds against animal cells have been isolated. However, phytotoxic substances from L. aspera have not yet been documented in the literature. Therefore, current research was conducted to explore the phytotoxic properties and substances in L. aspera. Aqueous methanol extracts of L. aspera inhibited the germination and growth of garden cress (Lepidum sativum) and barnyard grass (Echinochloa crus-galli), and the inhibitory activities were concentration dependent. These results suggest that the plant may have phytotoxic substances. The extracts were then purified by several chromatographic runs. The final purification was achieved by reversed-phase HPLC to give an equilibrium (or inseparable) 3:2 mixture of two labdane type diterpenes (compounds 1 and 2). These compounds were characterized as (rel 5S,6R,8R,9R,10S,13S,15S,16R)-6-acetoxy-9,13;15,16-diepoxy-15-hydroxy-16-methoxylabdane (1) and (rel 5S,6R,8R,9R,10S,13S,15R,16R)-6-acetoxy-9,13;15,16-diepoxy-15-hydroxy-16-methoxylabdane (2) by spectroscopic analyses. A mixture of the two compounds inhibits the germination and seedling growth of garden cress and barnyard grass at concentrations greater than 30 and 3 μM, respectively. The concentration required for 50% growth inhibition (I50) of the test species ranges from 31 to 80 μM, which suggests that the mixture of these compounds, are responsible for the phytotoxic activity of L. aspera plant extract.
糙苏（唇形科）是一种芳香草本植物，因其多种药用特性而闻名，并且已经分离出许多对动物细胞具有生物活性的化合物。然而，关于糙苏的植物毒性物质尚未见文献报道。因此，开展了当前的研究以探索糙苏中的植物毒性特性和物质。糙苏的甲醇水提取物抑制了水芹（独行菜）和稗草（稗）的萌发和生长，且抑制活性呈浓度依赖性。这些结果表明该植物可能含有植物毒性物质。然后通过多次色谱分离对提取物进行纯化。最终通过反相高效液相色谱实现纯化，得到两种半日花烷型二萜（化合物1和2）的平衡（或不可分离）3:2混合物。通过光谱分析将这些化合物鉴定为（相对构型5S,6R,8R,9R,10S,13S,15S,16R）-6-乙酰氧基-9,13；15,16-二环氧-15-羟基-16-甲氧基半日花烷（1）和（相对构型5S,6R,8R,9R,10S,13S,15R,16R）-6-乙酰氧基-9,13；15,16-二环氧-15-羟基-16-甲氧基半日花烷（2）。这两种化合物的混合物分别在浓度大于30 μM和3 μM时抑制水芹和稗草的萌发和幼苗生长。受试物种50%生长抑制（I50）所需的浓度范围为31至80 μM，这表明这些化合物的混合物是糙苏植物提取物植物毒性活性的原因。
