Analysis of Polyphenolic Content in Frequently Consumed Cereal Grains in China: Emphasis on Phenolic Acids

This study analyzed the polyphenol profiles of commonly consumed whole cereal grains. A total of 118 samples were collected from major online retail platforms, including six poaceae cereals (22 wheat, 21 triticale, 12 hulless barley, 7 oat, 7 naked oat, and 8 sorghum), 21 buckwheat samples (a pseudocereal from the polygonaceae family), and 12 refined wheat flour samples. Seven phenolic acids and five alkylresorcinol (ARs) homologs were quantified using high-performance liquid chromatography with photodiode array (HPLC-PDA) and fluorescence detection (HPLC-FLD), respectively. Total polyphenol content was calculated as the sum of all 12 compounds. The relative standard deviations (RSDs) for both methods were below 10%. Spike recovery rates ranged from 87.6% to 115.7% for phenolic acids and from 94.5% to 103.8% for ARs. Triticale, wheat, and hulless barley contained the highest total polyphenol levels, with ferulic acid as the predominant phenolic acid and ARs as the major polyphenols. Principal coordinates analysis (PCoA) and cluster analysis grouped the grains into five distinct categories, revealing clear profile similarities between wheat and triticale, and between oat and naked oat. Significant positive correlations among individual polyphenols were observed in the wheat–triticale group. These findings indicate that ARs are potential indicators of whole-wheat nutritional quality.