BACKGROUND: The expansion of Aedes aegypti (Diptera: Culicidae) population has increased the number of cases of arboviruses, in part due to the inefficiency and toxicity of the chemical control methods available to control this vector. We synthesized 19 chalcone derivatives and examined their activity against Ae. aegypti larvae in order to select larvicidal compounds that are non-toxic to other organisms. RESULTS: Seven chalcone derivatives (3a, 3e, 3f, 6a, 6c, 6d, and 6f) had lethal concentrations of substituted chalcones capable of killing 50% (LC 50) values lower than 100 mg mL −1 at 24 h post-treatment, which is the dose that the World Health Organization recommends for the selection of promising larvicides. The type of substituent added to (E)-1,3-diphenylprop-2-en-1-one (3a) markedly affected the larvicidal activity. Addition of chlorine, bromine and methoxy groups to the aromatic rings reduced the larvicidal activity, while replacement of the Bring (phenyl) by a furan ring significantly increased the larvicidal activity. The furan-chalcone (E)-3-(4-bromophenyl)-1-(furan-2-yl)prop-2-en-1-one (6c) killed Ae. aegypti larvae (LC 50 = 6.66 mg mL −1 ; LC 90 = 9.97 mg mL −1) more effectively than the non-substituted chalcone (3a) (LC 50 = 14.43 mg mL −1 ; LC 90 = 20.96 mg mL −1), and was not toxic to the insect Galleria mellonella, to the protozoan Tetrahymena pyriformis, and to the algae Chorella vulgaris. CONCLUSIONS: The substitution pattern of chalcones influenced their larvicidal activity. In the set of compounds tested, (E)-3-(4-bromophenyl)-1-(furan-2-yl)prop-2-en-1-one (6c) was the most effective larvicide against Ae. aegypti, with no clear signs of toxicity to other animal models. Its mechanism of action and effectiveness under field conditions remain to be determined.

We report the evaluation of chalcone derivatives as photosystem II (PSII) and plant growth inhibitors. Chalcone derivatives were evaluated as PSII inhibitors through Chl a fluorescence measurement. (E)-Chalcone (6a) and (E)-3-(4-bromophenyl)-1-(4-fluorophenyl)prop-2-en-1-one (6j) showed the best results, reducing the performance index on absorption basis parameter (PI abs ) by 70 %. Additionally, the decrease of TR 0 /RC and ET 0 / RC parameters indicates that the chalcone derivatives limited the number of active PSII reaction centers and the amount of trapped energy within them. Compounds 6a and 6j both act as post-emergent herbicides at 50 μM, reducing the root biomass of the Ipomoea grandifolia weed by 72 % and 83 %, respectively, corroborating the fluorescence results. The selectivity against weeds as compared to valuable crops by compounds 6a and 6j were evaluated employing Zea mays and Phaseolus vulgaris plants. In these, our newly synthesized compounds showed no effects on biomass accumulation of roots and aerial parts when compared to the control, providing valuable evidence for the role of these compounds as selective inhibitors of the growth of undesired weeds.

Reactive oxygen species (ROS), when in excess, cause damage to biomolecules (DNA, lipids, carbohydrates, and proteins), which are related to several pathologies. There is a growing study of substances that act to inhibit or reduce the action of these ROS. Chalcones are aromatic ketones with a naturally occurring and easily synthesized α,β-unsaturated system. In this work, we investigated the in vitro protective action of a new class of chalcones functionalized by the thiobarbituric acid reactive substances (TBARS) assay. The most promising molecule (Chalcone E) was submitted to the DPPH radical scavenging assay, and the MTT cell viability test evaluated its cytotoxicity. In addition, Chalcone E reduced lipid peroxidation, with maximum inhibition values of 73.05% for the brain, 81.42% for the liver, and 87.23% for the kidney, demonstrating a potential antioxidant effect. Still, the DPPH test did not observe this effect, suggesting further investigation of this molecule.