Differential Pharmacokinetics of Tetracycline and Sulfamethoxazole in Ipomoea aquatica Forsk Grown Hydroponically

Introduction: Veterinary antibiotics in edible vegetables have quietly become an increasing food safety concern as these antibiotics may find their way back to the human food chain through vegetable consumption. Although much has been studied on the deposit levels of antibiotics in plants, relatively little is known regarding the fate of antibiotics with time once they got entry to the plant.

Purpose: To investigate the pharmacokinetics (uptake, distribution, metabolism and elimination) of two commonly detected environmental antibiotic residuals, tetracycline (TC) and sulfamethoxazole (SMX), in vegetable Ipomoea aquatica Forsk.

Methods: The vegetable was grown on 100 μg/ml of drug in cultivation fluid for 24 hours, drug concentrations in roots, stem and leaves at 0, 0.5, 3, 6, 12 and 24 hours were quantified by HPLC-UV method and the bioaccumulation factors (BAF) were calculated. Drug biotransformation was determined by LC/MS/MS. Subsequently, the vegetable was exposed to fresh cultivation fluids for evaluation of drug elimination. 

Results: At 24 hours, for TC and SMX, the drug concentration was both highest in the root (30 and 6 μg/ml), followed by the leaves (10 and 5 μg/ml) and the stems (5 and 1 μg/ml). The BAF in tested tissues were either < 1 (TC) or < 0.1 (SMX), suggesting little accumulation. Drug biotransformation was not evident after one-week of growth. The elimination of drugs occurred mainly in the first 30 min, a total of 20% reduction for TC and 10% for SMX was recorded in 24 hours. Results were compared to those found in Brassica Chinensis L.

Significance: Differential pharmacokinetics existed for TC and SMX in Ipomoea aquatic Forsk and was different in Brassica Chinensis L. The ability of vegetables to quickly uptake micrograms of antibiotics in one day cannot be overlooked, but the deposition in the stems is minimal.