Application of liquid chromatography/mass spectrometry in assessment of potential use of azadirachtins (TreeAzin (TM)) against Asian longhorned beetle

Azadirachtins are natural triterpenoid compounds derived from Neem tree extracts with potential for use as systemic insecticides against invasive wood-boring insect pests. In this work, a sensitive and selective analytical method has been developed for the simultaneous determination of azadirachtin A and azadirachtin B (3-tigloylazadirachtol) in foliage and twigs of various tree species. Samples were mixed with C18 and primary-secondary amine (PSA), and extracted with acetonitrile. Then, an aliquot of the raw extract was 10-fold diluted with water and directly analyzed by liquid chromatography tandem mass spectrometry (LC-MS/MS). The method was validated in foliage and twig matrices of four different tree species (London Plane Tree, Red/Freemani Maple, Norway Maple and Sugar Maple) that are known hosts of the exotic invasive insect pest - Asian Longhorn Beetle (ALB). Analytical results for replicate (N = 5) samples, fortified at 0.01, 0.1 and 1 mg kg(-1), showed good recoveries (86-119%) and precision (< 20% RSD). The methodology was successfully applied to the analysis of 200 samples taken from a field experiment designed to investigate uptake, translocation and expression of azadirachtins in representative high-value urban trees followed by stem injection with TreeAzin (TM).