Insecticidal alkaloids from the seeds of Macleaya cordata on cotton aphid (Aphis gossypii)

Alcohol extracts from the seeds of Macleaya cordata have shown a significant insecticidal effect against the growth of the cotton aphid, Aphis gossypii Glover. In this study, we aimed to isolate the principal component of M. cordata to manifest its insecticidal effect on A. gossypii. The dried seeds of M. cordata were extracted with 80% aqueous methanol (MeOH), and the concentrated extracts were partitioned successively with ethyl acetate (EtOAc), n-butyl alcohol (n-BuOH), and H₂O. During the search for an insecticidal compound against the aphids, activityguided fractionation led to the isolation of two alkaloids from an n-BuOH fraction through repeated silica gel column chromatographic separations. Based on NMR, MS, and IR spectroscopic data, the chemical structures of the compounds were determined to be 8-hydroxydihydrochelerythrine (1) and 8-methoxydihydrosanguinarine (2) This is the first study in which 8-methoxydihydrosanguinarine was isolated from M. cordata. 8-Hydroxydihydrochelerythrine (1) and 8-methoxydihydrosanguinarine (2) decreased the survival of the cotton aphid by 76. 1±7. 9 and 73. 6±14. 6% at 100 ppm, respectively.