Structure-activity relationships of red cabbage anthocyanins from AAPH reactivity using HPLC-HRMS/MS and electrochemical detector

The antioxidant activity of anthocyanins in red cabbage (Brassica oleracea var. capitata f. rubra) was evaluated using a multi-method approach combining kinetic, chromatographic, and electrochemical techniques. While numerous studies have examined anthocyanin antioxidant activity using isolated assays, few have integrated kinetic measurements with electrochemical profiling. High-resolution HPLC-MS/MS enabled the identification and quantification of thirteen cyanidin-based derivatives, predominantly acylated with sinapic, ferulic, or p-coumaric acids. The radical-scavenging capacity was evaluated using a stopped-flow DPPH kinetic assay and a degradation protocol employing the radical initiator 2,2'-azodiisobutyramidine dihydrochloride (AAPH). Among the characterized compounds, cyanidin-3-(disinapoyl)-diglucoside-5-glucoside (Cy3(disin)diG5G) exhibited the highest degradation rate, possibly due to the presence of two sinapoyl moieties. Electrochemical profiling by HPLC-DAD-CAD showed that compounds with lower half-wave potentials (E_1/2) displayed greater reactivity. Cy3(disin)diG5G exhibited the lowest E_1/2 (+525 mV), confirming it as a highly reactive antioxidant. These findings suggest that structural features such as acylation and glycosylation, alter both the redox potential and degradation kinetics, which may contribute to a deeper understanding of the structure-activity relationships in polyphenolic antioxidants in food. The present work, with the integration of kinetic measurements and electrochemical profiling, could provide a more mechanistic and realistic assessment of antioxidant function in complex food matrices.