Evaluating the Phytotoxic Impact of Pharmaceutical Antibiotics on Spinach: Insights into Growth, Metabolism, and Protein Dynamics

The increasing presence of pharmaceutical contaminants, particularly antibiotics, in agricultural environments poses significant risks to crop health and productivity. This study investigated the phytotoxic effects of Azithromycin and Gentamicin on spinach ( Spinacia oleracea ) by assessing growth parameters, chlorophyll content, total phenolic content (TPC), total flavonoid content (TFC), and protein profile. Azithromycin at 10 mg/L enhanced seed germination, whereas it inhibited at higher concentrations of 100 and 500 mg/L. In contrast, Gentamicin promoted germination at all-tested concentrations relative to the control. Azithromycin treatment resulted in significant reductions in plant height, root length, chlorophyll a and b contents, total phenolic content (TPC), and total flavonoid content (TFC), indicating impaired growth and metabolic activity. While gentamicin exhibited moderate effects on these parameters, its impact was not statistically significant compared to that of azithromycin. SDS-PAGE analysis revealed qualitative alterations in protein profiles, suggesting disruption of protein synthesis or stability, which was further supported by quantitative protein estimation. Comparatively, azithromycin exerted significant effects on all evaluated parameters. This response may be attributed to its greater ability to penetrate plant tissues, where it can interfere with plastid (chloroplast) and mitochondrial ribosomes, thereby disrupting essential metabolic processes. In contrast, gentamicin likely remains confined to the extracellular spaces, resulting in minimal physiological impact. This study provides novel insights into the concentration-dependent phytotoxicity of Azithromycin in spinach, highlighting its impact on key phytochemicals and protein metabolism. These findings underscore the potential risks of specific antibiotic contamination in agricultural systems and contribute to understanding plant responses to emerging pharmaceutical contaminants.