Antioxidant and Anticancer Activities of Water Extracts from Flowers, Leaves and Stems of In Vitro Cultivated and Wild-Growing Marrubium vulgare Plants

<b>Background/Objectives:</b><i>Marrubium vulgare</i> L. is a medicinal plant with diverse pharmacological properties, yet its in vitro cultivation and the biological potential of aqueous extracts of the plant remain poorly studied. The present research aimed to establish an efficient in vitro propagation protocol and to compare the antioxidant and anticancer activities of freeze-dried water extracts from different parts (leaves, flowers, and stems) of in vitro cultivated and wild-growing <i>M. vulgare</i> plants. <b>Methods:</b> A micropropagation system was developed using Murashige and Skoog medium supplemented with kinetin and indole-3-acetic acid. Extracts from leaves, flowers, and stems were evaluated for the total polyphenol and flavonoid content, antioxidant capacity (ORAC, HORAC), and antiproliferative effects against HeLa, HT-29, and MCF-7 cancer cell lines. The mechanism of cytotoxicity was examined through apoptosis and cell cycle analysis. <b>Results:</b> The established protocol achieved high propagation efficiency (90% shoot formation). Cultivated leaves showed the highest polyphenol and flavonoid content and the strongest antioxidant activity. Aqueous extracts, particularly from leaves and flowers, displayed selective antiproliferative effects with HeLa cells being the most sensitive. The extracts induced apoptosis and cell cycle arrest -mainly at the G1 phase for cultivated plants and at both G1 and G2/M phases for wild plants. <b>Conclusions:</b> An efficient micropropagation protocol was successfully developed, providing a sustainable source of biologically active plant material. The study provides the first comprehensive comparison of <i>M. vulgare</i> water extracts from in vitro cultivated and wild-growing plants, linking phytochemical content with antioxidant and anticancer properties and highlighting both wild and in vitro cultivated plants, though wild plants in certain cases are generally more efficient, as promising candidates in natural anticancer therapeutics. The elevated flavonoid levels in in vitro cultivated plants, together with enhanced antioxidant capacity, indicate the strong potential of in vitro cultivated plants in antioxidant and cytoprotective formulations for cardiovascular, neurodegenerative, and metabolic diseases.