Polyphenolic Profiling of Plants and Edible Mushrooms to Aid Characterizing Polyphenol Oxidase Selectivity

Polyphenol oxidases are important metalloenzymes that catalyze the oxidation of polyphenols. Organisms can contain multiple isoenzymes whose possible different functionality is not understood. Moreover, their substrate preference is still unexplored, and a working hypothesis assumes their specificity is tailored to the substrates naturally present. Polyphenols are a broad molecular class whose presence in an organism is frequently unknown. Therefore, nine different mushrooms and plants were applied a LC-HRMS-based suspect screening workflow to investigate the polyphenols present. Overall, 401 features were annotated, composed of 221 flavonoids and 180 non-flavonoids. As 64% of the flavonoids were conjugated with a glycone, (semi-)quantification was applied when a reference standard of the aglycone was available. Isomers of hesperetin-O-glucoside were ubiquitous in all investigated samples. Additionally, a targeted LC-MS/MS assay covering 90 polyphenols was applied, showing phenolic acids as prevalent. This study provides new insights into the complex polyphenol profiles of nine mushroom and plant species.