Characterization of polyphenols in fruits and their influence on antioxidant activity of fruits

U ovom radu je, primjenom HPLC i spektroskopskih metoda, provedena karakterizacija polifenolnih spojeva: antocijanina, flavonola (kvercetin, miricetin, kemferol), flavanola ((+)- katehin, (-)-epikatehin), hidroksibenzojevih (p-hidroksibenzojeva, elaginska), hidroksicimetnih kiselina (p-kumarinska, kafeinska, ferulicna); koji su prisutni u borovnici, bobicama bazge, kupini, malini, višnji, trešnji, crnom i crvenom ribizu, jagodi i aroniji. Antioksidacijska aktivnost voća određena je primjenom DPPH i ABTS metode, a utjecaj polifenola na antioksidacijsku aktivnost voća ispitan je traženjem korelacije izmedu količine polifenola i antioksidacijske aktivnosti voća. Rezultati analiza pokazali su da se u ispitivanom voću nalaze vrlo velike količine ukupnih polifenola (od 1763 mg kg-1 u malini do 7194 mg kg-1 u aroniji) od kojih su najznačajniji antocijanini (od 169 mg kg-1u jagodi do 4069 mg kg-1 u borovnici). Sadržaj flavonola (od 4 mg kg-1 u malinama do 183 mg kg-1 u borovnici), flavanola (0-256 mg kg-1) hidroksicimetnih (12-92 mg kg-1) te hidroksibenzojevih kiselina (0-121 mg kg-1) znatno je manji. Iako se voće značajno razlikuje po količini, vrsti i rasprostranjenosti polifenola, aronija, borovnica, bobice bazge i crni ribiz mogu se izdvojiti po vrlo velikoj količini polifenolnih spojeva i vrlo visokoj antioksidacijskoj aktivnosti te bi ove vrste voća mogle poslužiti kao dobra sirovina u proizvodnji funkcionalne hrane. Visoke korelacije između antioksidacijske aktivnosti i sadržaja ukupnih polifenola, ukupnih antocijanina, ukupnih flavonola, ukupnih hidroksicimetnih kiselina te pojedinih polifenolnih spojeva (kafeinska kiselina, derivati cijanidina, p-kumarinska kiselina i kvercetin) pokazuju da ovi polifenolni spojevi imaju snažan utjecaj na ukupnu antioksidacijsku aktivnost voća, dok ostali istraživani polifenoli nisu značajni za ukupnu antioksidacijsku aktivnost. Ovi rezultati pridonose boljem objašnjenju antioksidacijske aktivnosti polifenola iz voća koji su bitni za pozitivno djelovanje voća u ljudskom organizmu.In this study, the characterization of polyphenolic compounds: anthocyanins, flavonols (quercetin myricetin, kaempferol), flavanols ((+)-catechin, (-)-epicatechin), hydroxybenzoic acids (p-hydroxybenzoic, ellagic) and hydroxycinnamic acids (p-coumaric, caffeic, ferulic; which are present in blueberry, elderberry, blackberry, red raspberry, sour cherry, sweet cherry, black currant, red currant, strawberry and chokeberry was carried out by using HPLC and spectroscopic methods. DPPH and ABTS assays were used to determine antioxidant activity of fruits. The correlation between the amount of polyphenols and antioxidant activity of fruits was investigated in order to examine the influence of polyphenols on antioxidant activity. The results showed that investigated fruits contained high amounts of polyphenols (from 1763 mg kg-1 in red raspberry to 7194 mg kg-1 in chokeberry) among which anthocyanins were the most important ones (from 169 mg kg-1 in strawberry to 4069 mg kg-1 in blueberry). The amount of flavonols (from 4 mg kg-1 in red raspberries to 183 mg kg-1 in blueberries), flavanols (0-256 mg kg-1), hydroxycinnamic (12-92 mg kg-1) and hydroxybenzoic acids (0-121 mg kg-1) was considerably lower. Fruits differ greatly in the amount, species and distribution of polyphenols but chokeberry, blueberry, elderberry and black currant stand out in high amounts of polyphenolic compounds and in strong antioxidant activity and could be used as a good raw material in production of functional foods. High correlations between antioxidant activity and amount of total polyphenols, total anthocyanins, total flavonols, total hydroxycinnamic acids, or the amount of individual polyphenolic compounds (caffeic acid, cyanidin derivatives, pcoumaric acid and quercetin) showed that these polyphenols have strong influence on total antioxidant activity of fruits whereas other investigated polyphenols were not significant for total antioxidant activity of fruits. Overall results are a contribution to better understanding of antioxidant activity of fruit’s polyphenols, the compounds that are important for positive action of fruits in human organism