Phytochemical Composition and Antioxidant Activity of Traditional Plant Extracts with Biocidal Effects and Soil-Enhancing Potential

This research provides a comprehensive evaluation of the phytochemical composition, antioxidant potential, and biological properties of four plant species with longstanding use in ethnobotanical traditions: <i>Calendula officinalis</i>, <i>Mentha</i> × <i>piperita</i>, <i>Urtica dioica</i>, and <i>Juglans regia</i>. Plant extracts were obtained using a range of solvent systems and subsequently analyzed for their content of total polyphenols, flavonoids, and phenolic acids. Ultra-high-performance liquid chromatography coupled with mass spectrometry (UHPLC-MS) enabled the accurate identification and quantification of major polyphenolic constituents. The antioxidant capacity was assessed through a series of in vitro assays, and elemental analysis was conducted to determine microelement content. To evaluate potential ecological implications, acute toxicity was tested using <i>Daphnia magna</i>, while phytotoxic effects were also examined. The results demonstrate pronounced antioxidant activity along with notable biocidal and soil-enhancing properties. These findings underscore the potential of such plant-based formulations as sustainable alternatives to conventional agrochemicals and highlight the relevance of integrating traditional botanical knowledge with modern strategies for enhancing soil quality, crop performance, and environmental sustainability.