Profiling the flavan-3-ol content of foods and beverages commonly consumed in the UK

Flavan-3-ols are an important subclass of (poly)phenols widely present in plant foods and beverages, occurring as monomers and oligomers (proanthocyanidins) (1) . Although databases such as US Department of Agriculture (USDA) and Phenol-Explorer (PE) report flavan-3-ol composition for some foods and beverages, these data are often based on unvalidated methods, and many commonly consumed foods and beverages remain uncharacterised. An AOAC-validated method has been applied to quantify flavan-3-ols in cocoa products (2) , but it has not been used across broader food categories. Given that daily intakes of 400-600 mg flavan-3-ols are associated with cardiovascular benefits (3) , accurate quantification is essential for assessing health outcomes and dietary recommendations. This study aims to provide the first comprehensive quantification of flavan-3-ols across a wide range of foods and beverages commonly available in UK supermarkets. A total of 131 food samples and 38 cocoa products were selected based on the flavan-3-ol content reported in the USDA and PE databases and purchased from UK supermarkets. Samples were desiccated and/or defatted, then extracted using the AWAA system (acetone:water:acetic acid = 70:29.5:0.5, v/v/v). Food and beverage extracts were purified using Strata SCX cartridges (55 μm, 70 Å, 500 mg/3 mL). Flavan-3-ols were quantified by Ultra-High-Performance-Liquid-Chromatography coupled with Fluorescence Detector (UHPLC-FLD). Calibration and quantification were performed using cocoa flavan-3-ol extracts with different degrees of polymerisation (DP) obtained from the National Institute of Standards and Technology (NIST). The optimised methodology was validated, in terms of linearity, selectivity, accuracy, precision, and low analyte levels. Flavan-3-ols were quantifiable in 75 of 131 food and beverage samples and in 34 of 38 cocoa products. Green tea showed the highest total flavan-3-ol content (2969 ± 106 mg/100 g fresh weight). Only 7 of 22 tested vegetables contained quantifiable flavan-3-ol monomers. Flavan-3-ols were detected in most fruits, nuts, seeds, and both non-alcoholic and alcoholic beverages. Tea, cocoa products, berries, and stone fruits were rich in flavan-3-ols, while fruit sauces, jams, and conserve contained negligible or trace amounts. All dark chocolates (n = 7) and most cocoa powders (n = 4) contained flavan-3-ols with DP1-DP7; no flavan-3-ols were detected in 3 out of the 4 white chocolates tested, while milk chocolates showed variable profiles. A strong positive correlation (r = 0.80) was observed between cocoa solids content and total flavan-3-ol concentration. The method showed good selectivity for all cocoa products and most samples, with good linearity, precision, and stability. This study represents the first comprehensive analysis of flavan-3-ols across a wide range of foods and beverages commonly available in UK supermarkets. These findings highlight the need for more accurate estimations of dietary intake to better evaluate health effects and support evidence-based recommendations.