Description

Poster. Abstract: Sorghum and maize are increasingly being recognised as sources of phenolic acids with health-benefiting antioxidant activity. These phenolic compounds are concentrated in the bran mainly in bound form. To release the intact etherified bonds, alkaline refluxing is employed for lengthy periods. Microwave assisted extraction (MAE) offers an alternative due to its rapidity, and a combination of high temperature and pressure. Microwave assisted extraction procedure was applied to sorghum and maize bran to release bound phenolic acids and sample solubilisation was achieved after 45s in 2 M NaOH. Phenolic acids were quantified and confirmed by HPLC-MS/MS. Ferulic acid (FA) and p-coumaric acid (PCA) were the only monomeric phenolics found in both cereal brans. The diferulic acids (DFA) 8-O-4′ and 8-5′ benzofuran form were found in sorghum bran and only the former in maize bran. The Contents of ferulic acid and diferulic acids in sorghum bran were at least 6 and 5 times less than in maize, respectively. Several phenolic acids have been reported in sorghum and maize although our findings showed few of these suggesting that MAE could have resulted in the thermal degradation of most phenolic acids. The large differences in phenolic acid Contents despite similarities in structure and chemical composition of these cereals suggest variations in their biosynthesis and cross-linking, hence affecting the degree of alkaline hydrolysis and breakage of ether bonds