Bioassay-guided isolation of potent aphicidal Erythrina alkaloids against Aphis gossypii from the seed of Erythrina crista-galli L

BACKGROUND The cotton aphid ( Aphis gossypii Glover) is one of the most invasive pests of cotton. Many botanical phytochemicals have a long history as a source of insecticides, and as templates for new insecticides. This study was undertaken to isolate aphicidal compounds from the seeds of Erythrina crista-galli L. using the bioassay-guided isolation method. RESULTS Three novel and 11 known Erythrina alkaloids were isolated. Erysodine ( 9 ), erysovine ( 10 ), erysotrine ( 8 ) and erythraline ( 11 ) showed moderate to excellent aphicidal activity with LD 50 values of 7.48, 6.68, 5.13 and 4.67 ng aphid –1 , respectively. The Potter spray tower bioassay gave corresponding LC 50 values of 186.81, 165.35, 163.74 and 112.78 µg ml –1 . A unique substructure, which presents an sp 3 methylene at C-8, a non-oxygenated site at N-9 and a conjugated dienes group (Δ 1,2 and Δ 6,7 ), plays a crucial role in the aphicidal activity. Application of erythraline ( 11 ) led to different increases in the activities of superoxide dismutase, catalase and glutathione S -transferase. CONCLUSION The study demonstrated that the Erythrina alkaloids erysodine ( 9 ), erysovine ( 10 ), erysotrine ( 8 ) and erythraline ( 11 ) have potential use as botanical aphicides for commercial application, or as templates for the development of new insecticides. © 2017 Society of Chemical Industry