Chemical characterization of proanthocyanidins in purple, blue, and red maize coproducts from different milling processes and their anti-inflammatory properties

Colored maize cultivars are drawing attention as economically viable sources of polyphenolic pigments, which may be used as a replacement of synthetic food dyes. Ingestion of polyphenolic compounds is also associated with potential health benefits. Proanthocyanidins (PA) are oligomeric and polymeric flavonoids. The objective was to evaluate the effect of dry milling, wet milling, and dry grind processes on coproduct yields of purple, blue, and red corn, and to determine the concentration and type of PA in various coproducts generated from these three processes. Furthermore, to evaluate their anti-inflammatory potential using biochemical assays. Highest PA concentrations were detected in purple maize coproducts. In wet milling process, steepwater contained the highest concentration of PA (170.3 ± 4.4 g catechin equivalent, eq/kg of maize on dry basis, db) followed by gluten slurry. In dry milling, pericarp contained the highest concentration (43.5 ± 2.1 g catechin eq/kg maize db), followed by small grits and large grits. Total PA recovered in wet milling were higher (204.3 ± 6.2 g catechin eq/kg maize db) compared to dry milling coproducts (91.0 ± 8.5 g catechin eq/kg maize db). PA degree of polymerization was below 10. PA from purple maize demonstrated anti-inflammatory effects inhibiting 66% of inducible nitric oxide synthase and 89% of cyclooxygenase-2 activities. Maize processing produces biologically active compounds with anti-inflammatory activity for potential pharmaceutical use.