Sustainable Characterization of Some Extracts of <i>Origanum vulgare</i> L. and Biosafety Evaluation Using <i>Allium cepa</i> Assay

<i>Origanum vulgare</i> L. is ethnomedicinally valuable against various diseases. In Romania, attention for the oregano extracts such as infusions, decoctions, or tinctures, which are very popular among consumers, is constantly increasing, mainly as an important therapeutic alternative. Therefore, this study was undertaken to evaluate the comparative cytotoxic and genotoxic effects of aqueous and hydroalcoholic extracts of local oregano using a sustainable method such as the <i>Allium cepa</i> assay. Two aqueous oregano extracts obtained by infusion (I01) and decoction (D02) and two hydroalcoholic extracts (E03—water/ethanol 80:20 <i>v</i>/<i>v</i>; E04—water/ethanol 60:40 <i>v</i>/<i>v</i>) were used in this study. Before performing the <i>Allium cepa</i> test, a phytochemical screening carried out using fast and efficient analytical methods (electrometry, colorimetry, UV-Vis spectrometry, and high-performance thin-layer chromatography/HPTLC) allowed the qualitative differences in the chemical profile of the investigated oregano extracts to be highlighted. The aqueous and hydroalcoholic oregano extracts were tested on root meristems of <i>Allium cepa</i> and the cytotoxicity and genotoxicity parameters evaluated were the mitotic index (MI) and chromosomal aberration (CA). The results revealed a decrease in MI for each analyzed sample, with hydroethanolic extract E04 showing the most significant effect on MI (9.66%, 3 times less than that of the control sample), followed by the D02 sample obtained by decoction. Chromosomal aberrations such as the ana-telophase with bridges, expelled chromosomes, or delayed chromosomes were observed in all four extracts. The frequency of cells with CA was higher in the case of samples treated with hydroalcoholic extracts compared to aqueous extracts. The experimental extraction conditions influenced the mitotic index, the varieties of identified chromosomal aberrations, and their frequency. Therefore, based on the result obtained in this study, it may be concluded that the <i>Oregano vulgare</i> L. extracts present cytotoxic and genotoxic effects on onion cells. The <i>Allium cepa</i> assay proves to be an easy-to-handle method, with reliable results, minimal cost, and environmental friendliness for the evaluation of the cytotoxic and genotoxic effects of oregano extracts.