Ovicidal and larvicidal properties of curcumin synthetic analogs against Caenorhabditis elegans and Meloidogyne exigua

Control methods for plant-parasitic nematodes encompass preventive strategies, such as the use of healthy seedlings and the implementation of conservation agriculture practices, in addition to chemical and biological nematicides. The most widely used nematicides are organophosphates and carbamates. However, the development of new nematicides has been limited, with only a few products introduced to the market. This study aimed to assess in vitro nematicidal properties of curcumin ( 1 ) and a series synthetic monoketone curcuminoid analogs ( 2–23 ) against the model nematode Caenorhabditis elegans and Meloidogyne exigua , a significant pest in coffee plantations across Brazil. An initial screening at 50 µM revealed that curcumin ( 1 ) and its more stable analog, curcumin A ( 2 ), were ineffective. In contrast, curcuminoid 3 induced 100% paralysis of C. elegans L3/L4 larvae. Curcuminoids 19 and 20 exhibited partial activity, paralyzing 75% and 55% of the larvae, respectively. EC ₅₀ assessments indicated that curcuminoid 3 was highly potent against both L3/L4 larvae and adults of C. elegans (EC ₅₀  < 6.25 µM). Notably, curcuminoid 3 completely inhibited egg hatching. In tests against M. exigua J2, curcuminoid 3 displayed activity, whereas compounds 19 and 20 had an EC ₅₀  > 90 µM. All tested synthetic monoketone curcuminoid analogs successfully inhibited egg hatching. The results demonstrated the potential of synthetic monoketone curcuminoid analogs as promising nematicide agents, particularly in inhibiting egg hatching. These findings enhance our understanding of the biological effects of curcuminoids and open new avenues for developing effective strategies to control plant-parasitic nematodes, providing valuable tools for agricultural pest management.