Extraction, structure characterization and biological activity determination of (S)-(-)-palasonin from Butea monosperma (Lam.) Kuntze seeds

Development of novel pesticides from natural products is an effective way to generate new insecticides. (S)-(-)-palasonin (PLN) is a natural compound from Butea monosperma (Lam.) Kuntze Seeds. The extraction process optimization, structural characteristics, and insecticidal activity of PLN are investigated in this study. Results show that extraction yields reach 0.668 ± 0.080 ‰ under the optimized extraction conditions: liquid-solid ratio of 10.4 mL/g, extraction temperature of 81.5 °C, and extraction time of 8.4 h. The yielded PLN structure was characterized by GC/MS, FT/IR NMR as well as X-ray single crystal diffraction. Notably, this is the first report of the single crystal structure of PLN. PLN exhibits the highest ingestion toxicity to Plutella xylostella (LC 50 : 10.72 mg L -1 at 48 h) and the highest contact toxicity to Periplaneta americana and Plutella xylostella (LD 50 : 0.08 μg/adult and 0.22 μg/larva). Moreover, PLN has high activity against the field-evolved multi-resistant strain of Plutella xylostella . We also found that PLN exerts an inhibitory effect (IC 50 : 1.79 μM) on the serine/threonine protein phosphatase type 5 (PP5c), and this inhibitory effect has a high correlation with insecticidal activity. PP5c is consequently proposed to be a crucial target of PLN. These results show that PLN has the potential to be developed as an innovative botanical insecticide for field control and management resistance of Plutella xylostella . Fig. Chemical structures and sources of (S)-(-)-palasonin and cantharidin. (a) Butea monosperma seeds and chemical structures of (S)-(-)-palasonin; (b) Meloidae insect and chemical structures of cantharidin. • An efficient extraction and purification method (S)-(-)-palasonin is provided. • (S)-(-)-palasonin has strong insecticidal activity against Plutella xylostella. • (S)-(-)-palasonin has the potential to manage the resistance of Plutella xylostella. • PP5c is a crucial target for (S)-(-)-palasonin to exert high insecticidal activity .