Title : Integrating EPR spectroscopy with LC-MS-based foodomics to elucidate radical-mediated antioxidant activity in Cascara (coffee husk)
Abstract:
Cascara (coffee husk), a by-product of coffee processing, is increasingly recognized as a source of bioactive compounds, particularly polyphenols. However, the relationship between its chemical composition and functional antioxidant activity remains insufficiently understood. This study applies an integrated analytical approach combining Electron Paramagnetic Resonance (EPR) spectroscopy with Liquid Chromatography–Mass Spectrometry (LC-MS) to investigate radical-mediated processes in cascara extracts. LC-MS analysis was used to characterize the profile of phenolic compounds, including chlorogenic acids and flavonoids. EPR spectroscopy with spin trapping (DMPO) enabled direct detection and semi-quantitative evaluation of reactive oxygen species and secondary radical species. To assess the contribution of metal-catalyzed reactions, selected experiments were conducted in the presence of metal chelators. Multivariate analysis (PCA/PLS) was applied to explore relationships between compound profiles and radical-related activity.
The results indicate that cascara exhibits a dual role, acting both as a source of antioxidants and a matrix capable of promoting radical formation under specific conditions, likely due to transition metal-mediated reactions. The intensity and kinetics of EPR signals were not directly proportional to total phenolic content, suggesting that specific compound classes and interactions within the matrix play a key role in modulating oxidative processes. This study highlights the importance of combining compositional and functional analyses to better understand the redox behavior of plant-based food matrices. The proposed approach provides a framework for evaluating the oxidative properties of food by-products within an evidence-based nutrition context.
