Antioxidative free and bound phenolic constituents in pericarp, germ and endosperm of Indian dent (Zea mays var. indentata) and flint (Zea mays var. indurata) maize

Distribution of phenolics in Indian dent and flint yellow maize was analyzed. HPLC and ESI-MS/MS results indicated that germ of maize samples contained significantly higher free phenolic acids than pericarp whereas, pericarp contained more bound phenolics. Free and bound phenolic acids in pericarp, germ and endosperm of dent maize were 267.5 ± 28.9 and 4329.6 ± 221.5; 468.7 ± 23.0 and 3428.6 ± 101.2; 6.2 ± 0.6 and 172.0 ± 11.1 µg/g, respectively, whereas in flint corn these values were 157.9 ± 27.4 and 5523.3 ± 292.2; 262.3 ± 20.8 and 1341.9 ± 80.6; 19.3 ± 1.3 and 224.0 ± 14.6 µg/g, respectively. Vanillic, syringic, p-hydroxybenzoic, protocatechuric, caffeic, p-coumaric and ferulic acids were detected among phenolic acids. Among flavonoids, cyanidin-3-O-glucoside, kaempferol and quercetin were also detected in trace amounts in the yellow maize. The pattern of radical scavenging by bound phenolic extract of pericarps varied between the samples. Peroxide scavenging and reducing capacity of botanical fractions also varied similarly. Free phenolics contributed 0.6–1.7, 5–15 and 46–60% to the anti-radical, peroxide scavenging and reducing capacity, respectively. Among lipophilic tocochromanols, γ-tocopherol was the most abundant homolog and varied significantly in its content for dent (29.4 ± 8.7 µg/g) and flint maize (63.2 ± 7.5 µg/g). Data show that dent and flint maize hold promise for the development of whole grain functional foods.