As 42% of the features were conjugated with a glycone (Fig. and.2), the concentration of these conjugated features (Table .9) was approximated based on the relative chromatographic peak area to their corresponding aglycone if a reference standard was available (Table .2). Standard addition was applied as the reference standards were spiked in the QC sample (Table .2). For certain analytes, the calibration curve in neat solvent was used as no change in peak area was observed after spiking due to high natural concentrations in the QC. Moreover, despite that the focus of the present study was to characterize the numerous polyphenols that are present with an untargeted workflow, the samples were also quantified with a broad targeted LC-MS/MS method (Table .10) to better define the concentrations of various polyphenols. Though the targeted LC-MS/MS method was not validated for the different matrices used here, it was previously validated for three complex bio-samples (urine, serum, and plasma) , demonstrating this general high selectivity and sensitivity. Moreover, for this method, the extraction efficiency and SSE were approximated for all the samples by enriching extra samples of white button mushrooms with the reference standards. Table .11 lists the five features of each sample from the untargeted workflow that had the largest chromatographic peak areas, the largest relative concentration, and the five analytes with the highest concentration from the targeted analysis. It is not unexpected that the most intense/concentrated polyphenols determined by the two alternative approaches may not match while some of the concentrations are in line with each other. This is due to inherent differences between the two analytical approaches. The untargeted method allows to investigate a far broader chemical space compared to the targeted method, but at the cost of reduced sensitivity due to the different LC-MS equipment required and its limited capacity for delivering full quantitative results.