In this Master’s thesis, we investigated the antioxidant (AOX) activity of soybean (Glycine max (L.) Merrill) extracts, with emphasis on the influence of extraction methods and genotypic differences. AOX activity was assessed using the spectrophotometric DPPH• assay (reaction kinetics), the TLC-DPPH• method with semi-quantitative evaluation (CI-AA index), and HPLC-DAD-MSⁿ for the identification and quantification of phenolic compounds. Statistical analyses (ANOVA, Kruskal-Wallis, regression) enabled comparisons between 16 extraction methods and 10 soybean varieties. The results showed that more polar solvents allowed for a higher yield of phenolic compounds but not necessarily higher AOX activity. Successive extractions confirmed that the removal of lipophilic compounds partly enhances AOX activity. Soxhlet extraction achieved the best results in both polar and nonpolar systems but altered the chemical profile of the extracts. Extracts obtained by magnetic stirring revealed that lipophilic AOX (tocopherols, carotenoids) and amphiphilic molecules remain underestimated in methods with polar solvents. The varieties showed moderate differences; 'Smuglyanka' stood out, being kinetically comparable to α-tocopherol (0.1 mM) and, in terms of DPPH• inhibition efficiency, to Trolox (0.1 mM). Correlation analysis showed the strongest relationship between AOX activity and glycosides (r² = 0.88), a moderate one with total phenolics (r² = 0.59), and for extraction methods, similar correlations for phenolics and glycosides (r² ≈ 0.64) but weak for aglycones (r² = 0.28). The findings indicate that glycosides are the key carriers of AOX activity in polar analytical environments and that the choice of extraction method and genotype critically determines AOX activity of soybean extracts.
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