Abstract
Coumarin is a natural compound well known for its phytotoxic potential. In the search for new herbicidal compounds to manage weeds, three synthetic derivatives bearing the coumarin scaffold (1–3), synthesized by a carbonylative organometallic approach, were in vitro assayed on germination and root growth of two noxious weeds, Amaranthus retroflexus and Echinochloa crus-galli. Moreover, the synthetic coumarins 1–3 were also in vitro assayed on seedlings growth of the model species Arabidopsis thaliana to identify the possible physiological targets. All molecules strongly affected seed germination and root growth of both weeds. Interestingly, the effects of synthetic coumarins on weed germination were higher than template natural coumarin, pointing out ED50 values ranging from 50–115 µM. Moreover, all synthetic coumarins showed a strong phytotoxic potential on both Arabidopsis shoot and root growth, causing a strong reduction in shoot fresh weight (ED50 values ≤ 60 µM), accompanied by leaf development and a decrease in pigment content. Furthermore, they caused a strong alteration in root growth (ED50 values ≤ 170 µM) and morphology with evident alterations in root tip anatomy. Taken together, our results highlight the promising potential herbicidal activity of these compounds.
Highlights
Weeds are still the most important pest because they compete with crops for water and nutrient resources reducing yields and quality and, causing huge economic losses [1,2,3,4]
A possible pathway leading to the coumarin derivatives involves the formation of a palladium phenate stabilized by triple bond coordination (I), followed by CO insertion, intramolecular syn insertion of the triple bond and alkoxycarbonylation of the resulting vinylpalladium intermediate (II)
We have evaluated the phytotoxic potential among widespread noxious weeds and Arabidopsis model plant of three coumarin derivatives, methyl (6-methoxy-2-oxo-2H-chromen-3-yl)acetate (1), methyl
Summary
Weeds are still the most important pest because they compete with crops for water and nutrient resources reducing yields and quality and, causing huge economic losses [1,2,3,4]. Large efforts should be undertaken to develop alternative methods for weed control, using eco-friendly, cost-effective and bioactive natural or natural-like products. These compounds could be used directly as bio-herbicides or as templates for the production of synthetic herbicides [8]. Leptospermone, a natural triketone found in the bottlebrush plant extract (Callistemon citrinus spp.) [10], is able to repress growth of several weeds [11,12] This compound was utilized to synthetize a more potent derivative, mesotrione (Callisto® herbicide), successfully employed as a pre-emergence and post-emergence herbicide. Cinmethylin, a herbicidal analogue of 1,4-cineole, is a moderately effective growth inhibitor used for monocotyledonous weed control [13], whereas pelargonic acid [14], sarmentine [15] and citral [16] are patented natural compounds isolated from plants, known for their high phytotoxic potential against the most common and noxious weeds
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