LAUSR

Flavonoids interferes with colorimetric protein assays in a concentration- and structure-dependent manner. Degree (≥3) and position (C3) of -OH substitution was associated with intensified interference (p<0.05). Significant overestimation of protein (∼3-5 folds) could occur at higher flavonoid concentrations (>5μM) and is particularly evident at lower protein concentrations (25-250 μg/ml). Since, healthy human urinary protein (<200 μg/ml) and flavonoids urinary excretion (0.5-2 μg/ml) levels fall in this range, overestimation of protein concentration with flavonoids consumption in diet, including natural supplements, remains relevant issue for diagnostic and research labs. Protein precipitation by acetone to remove interfering flavonoid successfully resolve the problem.