The effect of different solvents and acidifying reagents on the anthocyanin profiles and antioxidant capacity of purple corn

By-products (silk, cob, and husk) from purple corn processing are rich in anthocyanins, which can be used as natural antioxidants. In this work, the polyphenol and anthocyanin content and the chemical composition of solvent extracts from silk, cob, and husk were examined separately. The total anthocyanin (TAC) and polyphenols (TPC) content of purple corn silk is higher than the cob and husk. Ethanol can significantly improve the TAC in various purple corn extracts. Anthocyanins were identified using high-performance liquid chromatography coupled with an electrospray ionization mass spectrometer (HPLC-ESI-MS), and their composition was quantified using a diode matrix detector (DAD) coupled HPLC. The results of the quantitative analysis demonstrated that cyanidin derivatives were the main components of purple corn extracts, regardless of the solvent used. The selection of solvent and acidifier had a significant effect on the composition of anthocyanins. Ethanol and water can promote the dissolution of cyanidin derivatives, while methanol provides a solid incentive to extract peonidin derivatives. Formic acid may favor the production of malonyl anthocyanin, whereas hydrochloric acid may favor the production of succinyl anthocyanin. The results of the correlation analysis showed that the TAC primarily determined the antioxidant capacity of the purple maize extract in different extracts. The predictive evaluation of the VIP analysis shows that the higher relative concentration of C3dM, C3M, Pg3dM, and Pg3M in the water extract may contribute to its higher antioxidant power.