Determination of Neonicotinoids in selected fruits and vegetables and their impact on Nutritional Attributes

Abstract

The increased incidence of crop resistance to large number of insecticide has led to the development of new active ingredients which have been successfully applied to control pests in different agricultural and food commodities. Due to increased demand of food, research has been focused regarding the risks of food contaminated with pesticide residues. Hence, current study was designed to optimize and validate HPLC based determination of neonicotinoid residues including imidacloprid, acetamiprid, thiacloprid and thiamethoxam in selected fruits and vegetables and their effect on antioxidant potential and mineral profile. The selected fruits (guava and citrus) and vegetables (cauliflower, tomato and okra) were treated with neonicotinoid insecticides at a concentration of 0.5 mg/plant. The samples were harvested at different time intervals (0, 1, 7, 14, 21, and 28 days) after foliar spray and extracted using acetonitrile for neonicotinoid residues. High Performance Liquid Chromatography (HPLC) based method was validated successfully to analyze neonicotinoid residues. The antioxidant potential of selected fruits and vegetables was assessed at different harvest intervals in terms of their potential to hunt DPPH free radicals, ability to inhibit peroxidation in linoleic acid system and reducing power. The results regarding method validation evaluated that optimized HPLC-DAD method was linear over broad range of selected neonicotinoid concentrations. The residual levels of insecticides in selected fruits and vegetables at different time intervals revealed the decline in concentration (0.95-0.01μg/g) of neonicotinoids with the passage of time. Determination of neonicotinoid concentrations (0.5-0.95 μg/g) on the same day (after one hour of foliar spray) was higher than recommended Maximum Residue Limit (MRL), established by Codex Alimentarius Commission. After 7 days of foliar spray, only okra samples contained imadacloprid and acetamiprid residues (0.66 ± 0.02 and 0.58 ± 0.01) above than MRL (0.5μg/g). But these residues were not detected or found below MRL after 21 days of foliar application. The antioxidant behavior speculated that all fruits and vegetable contained good amounts of phenolic (2.53 ± 0.05 -63.18 mg Gallic Acid Equivalents (GAE)/g of extract) with substantial level of antioxidant activities following inclusive order as citrus > guava > okra > cauliflower > tomato. Overall, it was concluded that residues of neonicotinoid insecticides were within permissible limits after 21 days of foliar practices. However, neonicotinoids utilization in selected food commodities depleted the mineral profile but improved antioxidant character at the end of harvest interval (28 days). The study further suggested pre-harvest interval of 14 days for selected fruit and vegetables that would be optimistically safe according to health point of view.