Antioxidant and antimicrobial activities of phenolic acids rich extracts released from oat bran with the aid of carbohydrases.

摘要

Many studies have demonstrated that the health promoting capabilities of oats are due to the presence of antioxidants compounds, such as phenolic acids and avenanthramide (only present in oats), and also to dietary fibers (e.g. (β-glucan), and high content of lysine, a limiting amino acid in other cereals. Extraction of phenolic compounds in oat is difficult because up to 80% are conjugated with cell wall polysaccharides lipids. The aim of the research was to investigate the effect of four polysaccharide degrading enzymes on the release of polyphenols and biological properties of resulting polyphenol rich extracts.;The measurement of indices of antioxidant activities showed that treatment oat bran with the enzymes significantly increased radical scavenging and metal chelating capacities of samples. In the antimicrobial activity, viscozyme and cellulase treated samples had a significant inhibitory effect on the growth of the gram negative bacteria, E.coli.;The HPLC analysis showed the amount of free phenolic acids; such as ferulic acid and caffeic acid increased in samples treated with enzymes. The highest amount of caffeic acid was found in the alpha-amylase treated sample.;The pre-treatment of medium oat bran with the carbohydrases showed that more soluble phenolic acids were released and this was associated with increased antioxidant properties as well as inhibition of the growth of E. coli, a pathogen commonly encountered in foods. These data demonstrated that polysaccharide degrading enzymes could be used to obtain polyphenols rich fractions from bran (cereal by-products). This may find application in the formulation of nutraceuticals and functional food rich in antioxidants for health maintenance and reduction of risks of chronic diseases.;Aqueous solutions of medium oat bran flour were therefore treated with viscozyme, cellulase, alpha-amylase, and amyloglucosidase, and extracted with equal volume of methanol. Total phenolic content, antioxidant and antimicrobial activities of the extracts were determined. The effects on these enzymes on the release of individual phenolic acids were quantified using reverse-phase HPLC chromatography.