Department of Plant Sciences, University of Tennessee , Knoxville, Tennessee 37996, United States.
J Agric Food Chem. 2014 Jan 15;62(2):329-36. doi: 10.1021/jf404209d. Epub 2013 Dec 27.
One attractive strategy to discover more active and/or crop-selective herbicides is to make structural changes to currently registered compounds. This strategy is especially appealing for those compounds with limited herbicide resistance and whose chemistry is accompanied with transgenic tools to enable herbicide tolerance in crop plants. Bromoxynil is a photosystem II (PSII) inhibitor registered for control of broadleaf weeds in several agronomic and specialty crops. Recently at the University of Tennessee-Knoxville several analogues of bromoxynil were synthesized including a previously synthesized pyridine (2,6-dibromo-5-hydroxypyridine-2-carbonitrile sodium salt), a novel pyrimidine (4,6-dibromo-5-hydroxypyrimidine-2-carbonitrile sodium salt), and a novel pyridine N-oxide (2,6-dibromo-1-oxidopyridin-1-ium-4-carbonitrile). These new analogues of bromoxynil were also evaluated for their herbicidal activity on soybean (Glycine max), cotton (Gossypium hirsutum), redroot pigweed (Amaranthus retroflexus), velvetleaf (Abutilon theophrasti), large crabgrass (Digitaria sanguinalis), and pitted morningglory ( Ipomoea lacunose ) when applied at 0.28 kg ha(-1). A second study was conducted on a glyphosate-resistant weed (Amaranthus palmeri) with the compounds being applied at 0.56 kg ha(-1). Although all compounds were believed to inhibit PSII by binding in the quinone binding pocket of D1, the pyridine and pyridine-N-oxide analogues were clearly more potent than bromoxynil on Amaranthus retroflexus. However, application of the pyrimidine herbicide resulted in the least injury to all species tested. These variations in efficacy were investigated using molecular docking simulations, which indicate that the pyridine analogue may form a stronger hydrogen bond in the pocket of the D1 protein than the original bromoxynil. A pyridine analogue was able to control the glyphosate-resistant Amaranthus palmeri with >80% efficacy. The pyridine analogues of bromoxynil showed potential to have a different weed control spectrum compared to bromoxynil. A pyridine analogue of bromoxynil synthesized in this research controlled several weed species greater than bromoxynil itself, potentially due to enhanced binding within the PSII binding pocket. Future research should compare this analogue to bromoxynil using optimized formulations at higher application rates.
一种发现更有效和/或对作物更具选择性的除草剂的有吸引力的策略是对目前已注册的化合物进行结构改变。对于那些具有有限除草剂抗性且其化学性质伴随着转基因工具以实现作物中除草剂耐受性的化合物，这种策略特别有吸引力。溴苯腈是一种已注册用于控制几种农业和特种作物阔叶杂草的光系统 II（PSII）抑制剂。最近，田纳西大学诺克斯维尔分校合成了几种溴苯腈类似物，包括以前合成的吡啶（2,6-二溴-5-羟基吡啶-2-甲腈钠盐）、一种新的嘧啶（4,6-二溴-5-羟基嘧啶-2-甲腈钠盐）和一种新的吡啶 N-氧化物（2,6-二溴-1-氧化吡啶-1-鎓-4-甲腈）。这些溴苯腈的新类似物也在大豆（Glycine max）、棉花（Gossypium hirsutum）、反枝苋（Amaranthus retroflexus）、苘麻（Abutilon theophrasti）、马唐（Digitaria sanguinalis）和凹叶牵牛（Ipomoea lacunose）上进行了除草活性评估，施用量为 0.28 kg ha(-1)。第二项研究是在一种抗草甘膦杂草（Amaranthus palmeri）上进行的，化合物的施用量为 0.56 kg ha(-1)。尽管所有化合物都被认为通过结合在 D1 的醌结合口袋中而抑制 PSII，但吡啶和吡啶-N-氧化物类似物对反枝苋的活性明显强于溴苯腈。然而，嘧啶除草剂的应用对所有测试物种的伤害最小。使用分子对接模拟研究了这些功效的变化，表明吡啶类似物在 D1 蛋白的口袋中可能形成比原始溴苯腈更强的氢键。吡啶类似物能够以 >80%的功效控制抗草甘膦的马齿苋。溴苯腈的吡啶类似物显示出与溴苯腈相比具有不同的杂草控制谱的潜力。本研究合成的溴苯腈吡啶类似物控制了几种杂草物种，超过了溴苯腈本身，这可能是由于在 PSII 结合口袋中增强了结合。未来的研究应在更高的应用率下使用优化配方将该类似物与溴苯腈进行比较。
