Effect of the Phenological Stage on the Phenolic Composition, and Antioxidant and Antimicrobial Properties of Cirsium vulgare (Savi) Ten. Extracts

<i>Cirsium vulgare</i> (Savi) Ten. is a plant from the <i>Asteraceae</i> family that is commonly used in traditional medicine. The purpose of this work was to investigate the antioxidant and antimicrobial characteristics of phenolic compounds found in ethanol and dry extracts of <i>C. vulgare</i> leaves, inflorescence, and roots during various phenological stages. Apigenin-7-<i>O</i>-glucoside and chlorogenic acid were identified in practically all <i>C. vulgare</i> extracts. Extracts from leaves collected at the end of the phenological dormancy period and in the first growing year had the highest antioxidant (cupric ion-reducing antioxidant capacity of 12,938 Trolox equivalents/g dry weight) and antimicrobial activity (against <i>Staphylococcus aureus</i>, <i>Staphylococcus epidermidis</i>, <i>Pseudomonas aeruginosa</i>, <i>Proteus vulgaris</i>, and <i>Candida albicans</i>) with MIC values of ethanol extract from 16.7 mg/mL to 8.35 mg/mL. These extracts included a high concentration of chlorogenic acid and apigenin-7-<i>O</i>-glucoside. Also, dry extracts from <i>C. vulgare</i> roots and inflorescences showed a higher antimicrobial effect compared to ethanolic extracts with MIC values from 5.57 mg/mL to 3 mg/mL. The study emphasizes the critical role of phenological stages and raw material composition in the accumulation of phenolic compounds and their biological activity in <i>C. vulgare</i>. The findings suggest that extracts from <i>C. vulgare</i> leaves, especially those collected at the end of the phonological dormancy period, are promising candidates for further research into bioactive compounds with potential medicinal applications. The strong antioxidant and antibacterial properties of these extracts highlight their potential for development into natural pharmaceutical products.