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Phenolic compounds (acids and flavonoids) in fruits and fruit juices determined by UV/VIS spectroscopy and HPLC

Phenolic compounds in fruits and fruit juices have important influence on their quality and nutritional properties. These substances posses great chemical reactivity and they may participate in the complex enzymatic and non-enzymatic reactions during the juice production process. Chlorogenic acid is the predominant phenolic acid in fresh fruits and fruit juices, and quercetin is predominant flavonoid (there are some other flavonoids, but in minor quantities). Due to the biological properties of these compounds the aim of this research was to determine the level of some important flavonoids (quercetin, kaempferol and myricetin) and non-flavonoid compounds (chlorogenic acid) in the different fruits and fruit juices. Total phenols, flavonoids and chlorogenic acid were determined using UV/VIS spectrophotometric methods. Individual flavonoids were identified by HPLC using UV-Diode Array detection. Phenolic acids are the most abounded phenolic components in the investigated samples. Concentration of chlorogenic acid is the highest, while the flavonoids content is relatively low. Flavonoids content in the fresh fruits is much higher then that in the fruit juices, which means that they are lost during the juice production process so it is difficult to preserve them at original levels.

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