Toxicological insights into the non-target effects of ornidazole using the Allium cepa bioassay system

In this study, the biochemical and cytogenetic toxicity induced by the antibiotic active ingredient ornidazole in the non-target organism Allium cepa L. was investigated. In the toxicity assessment, the level of malondialdehyde (MDA), a biochemical marker of lipid peroxidation; genotoxicity indicators such as micronucleus (MN) frequency and mitotic index (MI); the incidence of chromosomal abnormalities (CAs); activities of antioxidant defense enzymes catalase (CAT) and superoxide dismutase (SOD); and the levels of chlorophyll a and b pigments reflecting photosynthetic capacity were analyzed. Additionally, DNA damage was assessed using the Comet test method, and the interaction of ornidazole with macromolecules-particularly DNA-was examined using the molecular docking approach. Four groups of A. cepa bulbs-one control and three treatments-were created. Three distinct dosages (0.0179, 0.0357 and 0.0714 mg/L) of ornidazole were used to germinate the bulbs in the treatment group, while tap water was used to germinate the bulbs in the control group. Following germination, samples from the roots and leaves were gathered and ready for examination. As a result, there was no cytogenetic damage or biochemical alteration that was statistically significant (p > 0.05) in the control group (Group I). MI value, DNA, and chlorophyll levels significantly (p < 0.05) decreased with ornidazole treatment, while MN frequency, CAs, MDA levels, SOD, and CAT activities significantly (p < 0.05) increased. At the ornidazole dosage of 0.0714 mg/L, these rises and declines were shown to be more noticeable. Ornidazole promoted several CAs in root meristem cells, the most common being the sticky chromosome. DNA damage was highlighted by the comet assay results, which indicated a drop in head DNA and an increase in tail DNA. In the control group, the Tail DNA was 1.00 ± 1.05 (%), whereas in the group treated with 0.0714 mg/L ornidazole, it increased to 72.0 ± 1.63 (5), indicating high DNA fragmentation. Molecular docking results showed ornidazole-DNA, ornidazole-tubulin, ornidazole-topoisomerase, ornidazole-glutamate-1-semialdehyde aminotransferase and ornidazole-protochlorophyllide reductase interaction supporting the biochemical and cytogenetic toxicity results. In conclusion, ornidazole exposure induced significant toxic effects in the non-target organism Allium cepa. The study further validated the efficacy of the Allium test as a reliable bioassay for detecting such toxicity. These findings underscore the urgent need for implementing appropriate environmental management strategies to mitigate pharmaceutical contamination and protect non-target organisms from drug-induced toxicity.