Aphicidal activities of Amaryllidaceae alkaloids from bulbs of Lycoris radiata against Aphis citricola
Aphids are one of the most destructive and economically important pests of plants on earth, causing severe financial losses worldwide. The extensive and unscientific use of insecticides has resulted in a universal zooming insecticide resistance among aphids across regions and substantial detrimental influences on the environment. This study investigates the insecticidal activity of alkaloids from L. radiata against A. citricola . The crude extract of Lycoris radiate showed a remarkable aphicidal activity against A. citricola . Ten known amaryllidaceous alkaloids were obtained according to the bioassay-guided isolation. The structures of these known alkaloids were identified as amabiline ( 1 ), deoxydihydrotazettine ( 2 ), deoxytazettine ( 3 ), 3-epimacronine ( 4 ), galanthamine ( 5 ), 11-hydroxygalanthamine ( 6 ), N -allylnorgalanthamine ( 7 ), 11 β -hydroxygalanthamine ( 8 ), lycorine ( 9 ) and colchicine ( 10 ). The results of aphicidal bioassay against A. citricola showed that compounds 1 - 9 exhibited considerable aphicidal activity with LD 50 values of 67.44, 76.33, 78.30, 96.70, 17.47, 32.60, 4.92, 20.33, 70.41 ng/aphid. N -Allylnorgalanthamine ( 7 ) possessed the highest aphicial activity, which was comparable with the commercial pesticide methomyl (2.91 ng/aphid). The results of in vivo AChE assay revealed that N -allylnorgalanthamine showed an obvious inhibitory effect on AChE in A. citricola in a time- and dose-dependent manner. The in vitro inhibition of AChE activity by N -allylnorgalanthamine was remarkable with an IC 50 value of 2.1 × 10 −8 M, which was 10 4 times stronger than the positive control methomyl with an IC 50 value of 4.2 × 10 –4 M. Meanwhile, N -allylnorgalanthamine can lead to an increase of the activities of SOD and CAT. The present work comprises the first report on insecticidal action of Amaryllidaceae alkaloids. N -Allylnorgalanthamine displayed a significant inhibition on AChE in Aphis citricola both in vivo and vitro . The insecticidal L. radiata extracts can be possibly used for controlling pests and isolated compounds, designing for new pesticides, can be the promising temples.
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