Chemical and biochemical studies on the effect of heat on some nuts: i. Phenolic content and it's antioxidant activities

ABSTRACT

Polar extracts of walnut, hazelnut and almond, with a significant antioxidant and antiradical activities, were found to contain phenolic acids and tannins with remarkable amount in walnut extract but it is less poor phenolic and flavonoid contents in hazelnut and almond extracts. Tannins content are hydrolysable tannins which are derivatives of gallic acid, hexahydroxydiphenic acid and ellagitannis, while the flavonoids content are very poor and mainly flavonols, which were determined by comparative chromatographic analysis with authentic samples of flavonoids to be glycosides of kaempferol, quercetin isorhamnetin with their aglycones and the flavanones catechin and epicatechin. A significant increasing of inhibition percentage effect with raising the temperature due to the increasing of the concentration of phenolic contents and not due to the change of the structure of the phenolic contents