Antioxidative free and bound phenolic constituents in botanical fractions of Indian specialty maize (Zea mays L.) genotypes

Specialty maize genotypes viz. QPM (quality protein maize), Baby corn, Popcorn and Sweet corn, which are usually consumed in whole forms can be good supplements of phenolic antioxidants. Botanical fractions of these maize genotypes were analyzed to explore the distribution of free and bound phenolics. HPLC and ESI-MS/MS results indicated the presence of vanillic, syringic, p-hydroxybenzoic, caffeic, p-coumaric, ferulic and isoferulic acids along with cyanidin-3-O-glucoside, kaempferol and quercetin. Germs of maize samples contained significantly higher free phenolics than pericarps, whereas, pericarps contained 74-83% of bound ones. QPM and Popcorn contained only 3% free phenolics whereas, Baby corn and Sweet corn had 14-17%. Unlike in peroxide scavenging and reducing capacity, anti-radical capacity of free phenolics of germs was significantly higher than that of pericarps. Free phenolics contributed 0.2-1.65%, 2-5% and 42-49% in anti-radical, peroxide scavenging and reducing capacity, respectively. Among lipophilic tocochromanols γ-tocopherol was the most abundant isomer in the samples among which Sweet corn contained the most (84.2 μg/g). Data showed that specialty maize genotypes are rich sources of hydrophilic and lipophilic bioactives and are natural antioxidants.