Monitoring the antioxidant status of woody plants using amperometric detection and solvents of different polarity

The antioxidant status of woody plants is linked to their adaptation to stress factors, including the influence of phytopathogens and agricultural practices. Information on methods for extracting natural plant antioxidants is contradictory or insufficient due to the complexity of the physicochemical extraction processes and analysis conditions. This study aims to investigate the extraction efficiency of antioxidants using extractants of different polarity in samples of a model woody plant. The following pure solvents and their mixtures in specified ratios were examined: distilled water (DW), water/ethanol 50:50 (W/E), water/ acetone 50:50 (W/A), acetone (AC), 96 % ethanol (ET), acetone/ethanol 50:50 (A/E50), acetone/ethanol 90:10 (A/E10), and dichloromethane (DCM). The antioxidant activity of the obtained extracts was assessed using an amperometric detector and standard antioxidants of various nature (ionol, quercetin, gallic acid). Additionally, the instrument sensitivity to these compounds was evaluated using mobile phases of varying acidity. The study experimentally demonstrated the high sensitivity of the method for detecting plant antioxidants using a gallic acid standard in the concentration range of 0.1–5 μg/ml. Water and acetone-ethanol solutions were identified as the most effective for extracting antioxidant compounds from plant samples (leaves and roots of the model plant), while acetone was most effective for samples of the multicomponent nutrient substrate (soil model). In leaf samples, the highest content of acid-soluble antioxidants was observed for: DW – 0.12–0.14 mg/g, A/E50 – 0.11 mg/g, and A/E10 – 0.19 mg/g. The highest content of the base-soluble antioxidants group was characterized for: DW – 0.53 mg/g, W/A – 0.41 mg/g, and A/E10 – 0.57 mg/g. Data on the antioxidant activity of root extracts showed maximum values for: A/E10 – 0.15 mg/g, DW – 0.14 mg/g, W/A – 0.11 mg/g – for acid-soluble antioxidants; and W/E – 0.4 mg/g, W/A – 0.43 mg/g, AC – 0.41 mg/g, A/E50 – 0.403 mg/g, A/E10 – 0.64 mg/g – for base-soluble antioxidants. The data on the antioxidant content in extracts from the soil substrate showed selectivity, with significant values obtained only for the AC variant – 0.6–3.2 mg/g.