Metabolic Profiling of Dietary Polyphenols and Methylxanthines in Normal and Malignant Mammary Tissues from Breast Cancer Patients

Scope Dietary polyphenols may protect against breast cancer. However, it is unknown whether polyphenols reach human malignant breast tumors in molecular forms and(or) at concentrations likely to act against cancer. Methods and Results Ninteen breast cancer patients consumed three capsules daily from biopsy‐confirmed diagnosis to surgery (6 ± 2 days). The capsules contained pomegranate, orange, lemon, olive, cocoa, and grapeseed extracts plus resveratrol, providing 37 different phenolics (473.7 mg), theobromine and caffeine (19.7 mg). A total of 101 metabolites are identified in urine, 69 in plasma, 39 in normal (NT), and 33 in malignant (MT) tissues by UPLC‐ESI‐QTOF‐MS. Eight control patients did not consume extracts. Phenolic‐derived metabolites in MT and NT are mainly glucuronidated and(or) sulfated. Some representative metabolites detected in MT (median and range, pmol g −1 ) are urolithin‐A‐3‐ O ‐glucuronide (26.2; 3.2−66.5), 2,5‐dihydroxybenzoic acid (40.2; 27.7−52.2), resveratrol‐3‐ O ‐sulfate (86.4; 7.8−224.4), dihydroresveratrol‐3‐ O ‐glucuronide (109.9; 10.3−229.4), and theobromine (715.0; 153.9−3,216). Metabolites, as detected in breast tissues, do not exert antiproliferative or estrogenic/antiestrogenic activities in MCF‐7 breast cancer cells. Conclusion This is the first study that describes the metabolic profiling of dietary phenolics and methylxanthines in MT and NT comprehensively. Although phase‐II conjugation might hamper a direct anticancer activity, long‐term tumor‐senescent chemoprevention cannot be discarded.