Antioxidant properties of fruit juices of six Viburnum opulus genotypes were evaluated by DPPH, ABTS(+) radical scavenging capacity (RSC), ferric reducing antioxidant power (FRAP), oxygen radical absorbance capacity (ORAC) and Folin-Ciocalteu total phenolic content (TPC) assays. TPC varied in the range of 5.4-10.6 mg gallic acid equivalents/g, RSC (ABTS(+)), FRAP and ORAC values were 31.9-109.8, 32.3-61.8 and 141.6-260.4 μmol trolox equivalents/g, respectively. V. opulus var. sargentii fruit juice was a remarkably stronger antioxidant than the other five V. opulus genotypes. The content of chlorogenic acid (the main phenolic compound in berry juices) depending on plant cultivar varied in the range of 0.54-6.93 mg/ml. The RSC of individual constituents was measured by the on-line HPLC-UV-DPPH method: chlorogenic acid was the dominant radical scavenger in V. opulus P3 (74%), while epicatechin and catechin (the main antioxidants in V. opulus var. sargentii) contributed to 40% and 23% of the total RSC for the sargentii genotype. Nine constituents were identified in V. opulus juice by using ultra high performance liquid chromatography coupled to quadruple and time-of-flight mass spectrometers (UPLC-QTOF-MS). In general, the study demonstrated that V. opulus var. sargentii followed by V. opulus P3 and V. opulus var. americanum possessed the highest antioxidant capacity. The obtained results may assist in selecting the most valuable V. opulus genotypes for the production of fruits possessing strong antioxidant capacity and containing beneficial phenolic constituents.
Keywords: Antioxidant activity; Catechins; Chlorogenic acid; Identification; Polyphenolics; Viburnum opulus.
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