Insecticide-Induced Perturbations in Sugar Metabolism and Alkaloid Biosynthesis in Coffea arabica (L.) Seedlings

The application of soil-applied insecticides can cause unintended metabolic changes on coffee plants, but these effects are still poorly understood. This study sought to assess the metabolic profile of coffee seedlings treated with insecticides commonly used for managing the coffee leaf miner (Leucoptera coffeella) using gas chromatography coupled to mass spectrometry (GC–MS). Coffee seedlings were treated via soil application with thiamethoxam, thiamethoxam + cyproconazole, dinotefuran, dinotefuran + pyriproxyfen, imidacloprid, and flupyradifuron, with water as the control treatment. After 80 days, the third pair of leaves was collected and analyzed using GC-MS. Insecticide treatments showed distinct metabolomic profiles (Student's t test, p < 0.05). Neonicotinoid applications generally increased the expression of free sugars, particularly impacting the galactose pathway, and consistently reduced inositol levels, suggesting a common metabolic cost. Notably, the butenolide flupyradifurone triggered a unique response, distinguished by the considerable accumulation of the neuroactive alkaloid N-methylphenylethanolamine, putatively identified by mass spectral library matching. This study demonstrates that insecticides induce specific and complex metabolic shifts in coffee seedlings, offering essential understanding into their biochemical effects beyond pest control.