(+/-)-catechin: chemical weapon, antioxidant, or stress regulator?
(+/-)-catechin: chemical weapon, antioxidant, or stress regulator?
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DOI：
10.1007/s10886-009-9681-x
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发表时间：
2009-08
影响因子：
2.3
通讯作者：
Hadacek, Franz
中科院分区：
文献类型：
--
作者：
Chobot, Vladimir;Huber, Christoph;Trettenhahn, Guenter;Hadacek, Franz
关键词：
（±）-儿茶素是一种黄烷-3-醇，存在于许多植物物种的器官中，尤其是水果。对健康有益的作用已被广泛研究，尚未发现明显的毒性作用。相反，（±）-儿茶素被认为是一种“化学武器”，由Centaurea stoebe的根部分泌，Centaurea stoebe是北方美洲的一种入侵性矢车菊。最近，基于（±）-儿茶素的低植物毒性、在高于5的pH水平下的不稳定性以及从土壤中的回收率差，这一假设已被拒绝。在目前的研究中，（±）-儿茶素并没有抑制发展的白色和黑色芥末的程度，相当于高植物毒性的胡桃醌，萘醌，据称是负责核桃树的化感作用。在高应力水平，造成亚致死浓度的甲醇在培养基中，和12小时的光周期，（±）-儿茶素甚至衰减生长迟缓。当测定（±）-儿茶素对卤虫死亡率时，观察到类似的效果。较高的浓度降低了由甲醇毒性浓度引起的死亡率。此外，当在脱氧核糖降解测定的变体中测试（±）-儿茶素时，当活性氧物质（ROS）以较高浓度存在时，它是活性氧物质（ROS）的有效清除剂。当铁被（±）-儿茶素直接螯合时，这种抗氧化作用增强。相反，如果铁螯合到EDTA上，则在较高浓度下表现出促氧化作用;在这种情况下，（±）-儿茶素将分子氧和铁还原为芬顿反应所需的试剂，以产生羟基自由基。循环伏安图的（±）-儿茶素与植物毒性萘醌胡桃醌的比较表明，两种化合物的氧化还原循环特性相似，虽然胡桃醌需要较低的电化学电位进入氧化还原反应。在缓冲溶液中，（±）-儿茶素在pH3.6（液泡）中保持稳定，24 h后在pH7.4（细胞质）中分解。这些结果支持了最近拒绝的假设，（±）-儿茶素可能作为一种“化学武器”的入侵植物。相反，（±）-儿茶素的积累和分泌可能有助于植物在逆境中生存。
(±)-Catechin is a flavan-3-ol that occurs in the organs of many plant species, especially fruits. Health-beneficial effects have been studied extensively, and notable toxic effects have not been found. In contrast, (±)-catechin has been implicated as a ‘chemical weapon’ that is exuded by the roots of Centaurea stoebe, an invasive knapweed of northern America. Recently, this hypothesis has been rejected based on (±)-catechin’s low phytotoxicity, instability at pH levels higher than 5, and poor recovery from soil. In the current study, (±)-catechin did not inhibit the development of white and black mustard to an extent that was comparable to the highly phytotoxic juglone, a naphthoquinone that is allegedly responsible for the allelopathy of the walnut tree. At high stress levels, caused by sub-lethal methanol concentrations in the medium, and a 12 h photoperiod, (±)-catechin even attenuated growth retardation. A similar effect was observed when (±)-catechin was assayed for brine shrimp mortality. Higher concentrations reduced the mortality caused by toxic concentrations of methanol. Further, when (±)-catechin was tested in variants of the deoxyribose degradation assay, it was an efficient scavenger of reactive oxygen species (ROS) when they were present in higher concentrations. This antioxidant effect was enhanced when iron was chelated directly by (±)-catechin. Conversely, if iron was chelated to EDTA, pro-oxidative effects were demonstrated at higher concentrations; in this case (±)-catechin reduced molecular oxygen and iron to reagents required by the Fenton reaction to produce hydroxyl radicals. A comparison of cyclic voltammograms of (±)-catechin with the phytotoxic naphthoquinone juglone indicated similar redox-cycling properties for both compounds although juglone required lower electrochemical potentials to enter redox reactions. In buffer solutions, (±)-catechin remained stable at pH 3.6 (vacuole) and decomposed at pH 7.4 (cytoplasm) after 24 h. The results support the recent rejection of the hypothesis that (±)-catechin may serve as a ‘chemical weapon’ for invasive plants. Instead, accumulation and exudation of (±)-catechin may help plants survive periods of stress.
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