Methoxychalcones and Cinnamaldehyde as Herbicidal Compounds

Synthetic compounds inspired by natural products provide innovative herbicide leads. Here, 18 methoxychalcones, inspired by cinnamaldehyde and curcumin, were designed, synthesized, and evaluated for their herbicidal activity. Additionally, cinnamaldehyde and curcumin were also assessed. Laboratory and greenhouse bioassays evaluated the inhibition caused by the compounds on initial growth in lettuce and weeds. In laboratory settings, 4’-hydroxy-3′-methoxychalcone induced the highest inhibition for lettuce root (66%) and shoot length (53%) compared to the negative control. The compounds 4’-hydroxy-3′-methoxychalcone and cinnamaldehyde inhibited about 87% of Urochloa decumbens growth, making them the most effective in reducing initial weed growth. Chalcones displayed no selectivity, inhibiting the growth of monocotyledonous and eudicotyledonous species. Additionally, 4’-hydroxy-3′-methoxychalcone caused 50% injury in Raphanus raphanistrum under greenhouse conditions. Chalcones and cinnamaldehyde hold promise for developing herbicides. Additional studies assessing the combined effects of methoxychalcones would be valuable to determine whether their herbicidal activity can be intensified.