Antioxidační komplex bioflavonoidů a askorbové kys. v jablkách

Antioxidační komplex bioflavonoidů a askorbové kyseliny v jablkách

( Malus pumila Mill.).

Abstract: Polyphenolic compounds esp. flavonoids and ascorbic acid are effective antioxidants regarding their ability to react with free radicals of fatty acids and oxygen (free radical scavenging effect). One of the richest sources of flavonoids in human nutrition are apples (Malus pumilla Mill.) that contain abundant complex. Their flavonol content decreases in great deal atherosclerotic processes, inhibits from cholesterol accumulation in blood serum and enhances resistance of vascular walls and decreases risk of coronary heart disease.

In review article is given information about the composition of flavonoid complex of apples that represent rich source of dominant flavonol - quercetin - in human nutrition. Apples are also rich source of other antioxidants as ascorbic acid that forms with antioxidant net work of flavonoids that influences anticancerogenic properties of these compounds.

Polyphenolic complex of apples includes glycosides of flavonols, ie. glycosides of kaempferol - astragalin (3-O-glucoside), glycosides of quercetin - quercitrin - (3-O-rhamnoside), isoquercitrin (3-O-glucoside), hyperoside (3-O-galactoside), 3-O-xyloside, avicularin (3-O-arabinoside) and rutin (3-O-rutinoside). The other flavonoid compounds are flavanones, esp. naringin (naringenin-7-O-rhamnoglucoside), dihydrochalcone phloretin and eriodictyol-7-O-glucoside. As dominant red colorant of apples was determined cyanidine -3-O-galactoside (95 - 100 mg anthocyanins in kg of apples). The most manifested compound is chlorogenic acid, from anthocyanes cyanidine-3-O-galactoside > cyanidine-3-O-glucoside > cyanidine-3-O-arabinoside > cyanidine-3-O-xyloside. The quercetin content in apples is 21 - 72 mg.kg-1 dependent on cultivar. For apples are typical leucoanthocyanidins. From phenolcarboxylic acids are manifested p-coumaric, protocatechuic, o-coumaric, vanillic and p-hydroxyphenylacetic acid, from flavan-3-ols and flavan-3,4-diols (+)-catechin, (-)-epicatechin and di-, tri-, and tetramers of procyanidins. An important constituent of the antioxidant complex of apples is ascorbic acid (1.8 - 6.4 mg.100 g-1).

In review article is discussed influence of extrinsic and intrinsic factors influencing polyphenolic antioxidants content (varietal differences, influence of locality, year, maturation, pre-harvest treatment, storage, technological ways of processing). It is discussed the influence of polyphenol contents on resistance of apple trees. Resistant cultivars contain higher amounts of p-coumaric acid and flavanols. During storage there is apparent decrease of both ascorbic acid and polyphenols. Contents of anthocyanes and chalcones are in positive correlation with resistance of trees to low and variable temperatures. During maturation of apples it could be determined synthesis and accumulation of polyphenols (esp. anthocyanes) and ascorbic acid. Meanwhile polyphenols are substrates of polyphenol oxidases in the process of enzymic browning, ascorbic acid is a natural inhibitor of this browning deterioration. Process of enzymic browning of apples and apple juices is inhibited with ascorbic and citric acids addition to apple products. Polyphenol content could be influenced by pre-harvest and technological procedures.

Key words: Apples; flavonoid antioxidants; flavonols; anthocyanes; chalcones; phenolcarboxylic acids; ascorbic acid; varietal differences; influence of year; influence of maturity; changes during storage