Biological activity of coumarins against Spodoptera frugiperda (Lepidoptera: Noctuidae)

In this work, we evaluated the activity of coumarins against larvae Spodoptera frugiperda in a group of compounds (1-7) purchased from SIGMA-ALDRICH (96% purity, as informed by the manufacturer) and a group of coumarin derivatives (compounds 8-15) synthesized according to suitable chemistry procedures. Coumarins were synthesized by the Pechmann method under solvent-free conditions using a bulk Keggin heteropolyacid. The compounds represent a valuable resource for future studies of plant chemical defense. Results indicate that coumarins: (12) 7-methyl-3,4-dimethyl-2H-chromen-2-one, (14) 7-hydroxy-3,4 dimethyl-2H-chromen-2-one, and (15) 4-methyl-2H-benzo[h]-chromen-2-one have highly significant insect growth regulatory activity. Furthermore, sublethal effects were observed such as pupal mortality and adult deformities. Compounds (13) 4,6,7-trimethyl-2H-chromen-2-one and (14) 7-hydroxy-3,4 dimethyl-2H-chromen-2-one caused pupal mortality higher than 40%. The quantitative structure-activity relationships were determined using the available data with the purpose of predicting the toxicity activity of a number of structurally related coumarins. A molecular structure and biological activity relationship is suggested. The observed effects were in part produced by severe alterations of the epithelial cells of the midgut.