2.7. Sample Preparation
The frozen urine samples were thawed at room temperature and subjected to different extraction procedures and analytical methods based on the compound of interest. A brief description of these procedures is provided below.Urinary tartaric acid was measured after slightly modifying and validating a previously published method [For the rest of the metabolites, including F2-isoprostane, resveratrol, quercetin, and catechin, previously published methods [