Radioprotective potential of Ophioparma ventosa (L.) Norman extract against UV-C-induced damage in Allium cepa

Ultraviolet-C (UV-C) radiation is capable of inducing severe physiological, cytogenetic, and biochemical disturbances in living organisms. Increasing exposure to artificial UV-C sources has intensified the search for natural radioprotective agents. Thanks to their unique antioxidant compounds and natural UV-filtering metabolites, lichens are able to withstand high levels of ultraviolet radiation. This study evaluated the protective potential of Ophioparma ventosa (L.) Norman lichen extract against adverse effects of UV-C in Allium cepa L., a well-established bioindicator for genotoxicity and oxidative stress assessment. Onion bulbs were exposed to 254-nm UV-C radiation alone or in combination with two concentrations of aqueous extract of O. ventosa (0.5 g/L and 1.0 g/L) for 72 h. Physiological parameters including germination percentage, root elongation, and weight gain were assessed. Genotoxic effects were evaluated using mitotic index (MI), micronucleus (MN) frequency, chromosomal aberrations (CAs), and DNA fragmentation (Comet assay). Malondialdehyde (MDA), proline levels, superoxide dismutase (SOD) and catalase (CAT) activities, and chlorophyll a and b contents were determined as oxidative stress markers. In addition, meristematic cell integrity was examined microscopically, and phenolic constituents of the extract were characterized by LC-MS/MS. UV-C exposure suppressed root growth, reduced MI, increased MN and CAs frequencies, elevated DNA fragmentation, and enhanced oxidative stress biomarkers, confirming its strong cytotoxic and genotoxic potential. Applied doses of the O. ventosa extract alone did not induce toxicity on A. cepa. In contrast, co-application of O. ventosa extract significantly mitigated these adverse effects in a dose-dependent manner. LC-MS/MS analysis revealed the presence of phenolic compounds, including p-coumaric acid, gallic acid, vanillin, gentisic acid and taxifolin, which likely contribute to the observed antioxidant and protective effects. Findings of the present study demonstrate that O. ventosa possesses radioprotective capacity against UV-C toxicity and highlight its potential as a natural bioresource for mitigating radiation-related oxidative and genotoxic stress in plant systems.