The extracts of the twigs and leaves of Murraya microphylla showed different level herbicidal activities against Amaranthus retroffexus and Digitaria sanguinalis. Bioguided isolation was performed to obtain eight pyranocarbazoles (1-8), four coumarins (10-13), two flavones (15 and 16), one dibutyl phthalate (9), and one sterol (14), including a new pyranocarbazole (1) and a new natural product (9). Petri dish assay showed that pyranocarbazoles and coumarins were the main herbicidal components of M. microphylla extract, and their structure–activity relationships were ulteriorly elucidated. As the representatives of pyracarbazole and coumarin, 7 and 10 showed significant herbicidal activity compared with the positive control (Nicosulfuron), with the IC₅₀ values 82.93 and 16.34 μg mL⁻¹ against shoots and roots of A. retroffexus seedling, respectively. Experimental results of morphology, physiology and biochemistry indicated that the inhibition on seed germination by 7 and 10 was mainly related to energy deficiency, while the inhibition of seedling growth was mainly related to decreased chlorophyll content, reduced root hairs, and cell membrane damage. Therefore, 7 and 10 have the potential to develop new plant herbicides directly or as lead compounds.

中文翻译：

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Murraya microphylla 分离株的除草活性和生化特性


Murraya microphylla 的枝叶提取物对 Amaranthus retroffexus 和 Digitaria sanguinalis 表现出不同程度的除草活性。进行生物引导分离，获得 8 种吡咯咔唑 （1-8）、4 种香豆素 （10-13）、2 种黄酮 （15 和 16）、1 种邻苯二甲酸二丁酯 （9） 和 1 种甾醇 （14），包括一种新的吡咯咔唑 （1） 和一种新的天然产物 （9）。培养皿实验表明，吡咯咔唑类和香豆素类是小叶苔藓提取物的主要除草成分，其构效关系被明确。作为吡咯卡唑和香豆素的代表，与阳性对照 （烟嘧磺隆） 相比，7 和 10 表现出显着的除草活性，IC₅₀ 值分别为 82.93 和 16.34 μg ^mL-1 对 A. retroffexus 幼苗的芽和根。形态学、生理学和生化实验结果表明，7和10对种子萌发的抑制主要与能量不足有关，而对幼苗生长的抑制主要与叶绿素含量降低、根毛减少和细胞膜损伤有关。因此，7 和 10 有可能直接开发新的植物除草剂或作为铅化合物。