Molecular signatures of amoxicillin phytotoxicity revealed by integrated cytogenetic, biochemical, and molecular docking analyses

Amoxicillin, one of the most frequently prescribed β-lactam antibiotics in both human and veterinary medicine, is released into the environment due to its widespread use; it enters aquatic ecosystems and especially the food chain, posing potential risks to non-target organisms. This study aimed to investigate the genotoxic and oxidative stress-inducing effects of amoxicillin in Allium cepa meristematic cells. To evaluate toxicity, mitotic index (MI), micronucleus (MN) frequency, chromosomal abnormality (CAs), malondialdehyde (MDA) level, superoxide dismutase (SOD) and catalase (CAT) activities, and chlorophyll ( a and b ) contents were used as key indicators. In addition, the Comet assay assessed DNA integrity, and molecular docking was performed to evaluate amoxicillin interactions with DNA, proteins, and enzymes. Analysis of these parameters made it possible to determine the oxidative damage caused by the toxic impact of amoxicillin on Allium cepa plant cells. A. cepa bulbs were allocated into four groups, comprising one control and three treatment groups, and were germinated in tap water (control), 36, 71, and 142 µg/L amoxicillin solutions, after which root and leaf tissues were harvested for subsequent analyses. Exposure to amoxicillin markedly suppressed cell division, induced DNA damage, disrupted chlorophyll biosynthesis, and enhanced oxidative stress in Allium cepa . These alterations were evidenced by a reduced mitotic index and chlorophyll contents, together with increased MDA levels, SOD and CAT activities. In the Comet assay, a decrease in head DNA percentage and an increase in tail DNA percentage were observed with increasing amoxicillin concentrations. Molecular docking analyses suggested that amoxicillin may interact with DNA, tubulin proteins, topoisomerase enzymes, and enzymes involved in chlorophyll biosynthesis, providing mechanistic support for the experimentally observed genetic and biochemical alterations. This study provides the first integrated evidence that environmentally relevant concentrations of amoxicillin induce genotoxicity and oxidative stress in Allium cepa , supported by cytogenetic, biochemical, Comet, and molecular docking analyses, thereby providing new mechanistic insights for the environmental risk assessment of amoxicillin.