Comprehensive evaluation on phenolic derivatives and antioxidant activities of diverse yellow maize varieties

The main phenolic derivatives and antioxidant capacity of ninety-three yellow maize varieties were investigated, together with their color parameters. Sixteen phenolics were identified in the free extract by UPLC-ESI-MS/MS, N', N″-diferuloyl putrescine and N', N″-dicoumaryl spermidine were the major phenolic derivatives. Fourteen phenolic compounds were found in the bound extract, with trans-p-coumaric acid, trans- and cis-ferulic acid being the predominant phenolic acids. The orange-yellow maize varieties presented the highest total phenolic content (TPC) and total flavonoid content (TFC), along with significantly higher antioxidant potential. Correlation analysis showed that b* value (corresponding to yellow degree) was positively correlated with the total carotenoid content (TCC), phenolic content, and antioxidant capacity (p < 0.05). Through Hierarchical Clustering Analysis (HCA), the 93 maize varieties could be divided into three categories according to b* value and antioxidant activity. The heatmap visualization further underscored the component differences across various varieties, unveiling the intricate phytochemical profiles of these maize varieties.