Azadirachtin-A and tetrahydroazadirachtin-A concentrates: preparation, LC-MS characterization and insect antifeedant/IGR activity against Helicoverpa armigera (Hübner).
A 60% azadirachtin-A concentrate has been obtained through repeated precipitation with hexane from a methanolic solution of a 20% concentrate. Azadirachtin-A (90%) has been obtained by medium-pressure liquid chromatography of the 60% concentrate with an RP-18 column and a methanol + water (1 + 1 by volume) solvent system. Catalytic hydrogenation of the 60 and 90% azadirachtin concentrates yielded the corresponding tetrahydroazadirachtin concentrates. Dihydroazadirachtin and tetrahydroazadirachtin formed during the first 5 h of hydrogenation were identified by LC-ESI-MS on the basis of their unique mass fragmentation pattern. The efficacy of tetrahydroazadirachtin concentrates in inhibiting the feeding and growth of Helicoverpa armigera (Hübner) larvae has been compared with that of azadirachtin concentrates. They were in general more active and deterred larvae from feeding at all concentrations. Tetrahydroazadirachtin-A (90%) and azadirachtin-A (90%) with respective IC(50) values of 280 and 390 mg L(-1) were effective as insect growth regulators, while tetrahydroazadirachtin-A (90%) displayed higher antifeedant activity (AI(50) 14 mg L(-1)) against the test insect.
Sharma
Vandana
V
Division of Agricultural Chemicals, Indian Agricultural Research Institute, New Delhi 110 012, India.
Walia
Suresh
S
Dhingra
Swaran
S
Kumar
Jitendra
J
Parmar
Balraj S
BS
D000818:Animals; D002853:Chromatography, Liquid; D005247:Feeding Behavior / Q000187:drug effects; D006865:Hydrogenation; D007306:Insecticides / Q000138:chemical synthesis* / Q000737:chemistry; D007814:Larva; D007915:Lepidoptera; D036701:Limonins / Q000138:chemical synthesis* / Q000737:chemistry / Q000633:toxicity; D013058:Mass Spectrometry
D007306:Insecticides; D036701:Limonins; C514548:tetrahydroazadirachtin-A; C010329:azadirachtin