Berry Phenolics Research Articles

Antioxidant Activity of Berry Phenolics on Human Low-Density Lipoprotein and Liposome Oxidation

The antioxidant activity of phenolic compounds present in berries was investigated by two copper-catalyzed in vitro oxidation assays: human low-density lipoproteins (LDL) and lecithin liposomes. The amount of total phenolics varied between 617 and 4350 mg/kg in fresh berries, as gallic acid equivalents (GAE). In LDL at 10 μM GAE, berry extracts inhibited hexanal formation in the order: blackberries > red raspberries > sweet cherries > blueberries > strawberries. In lecithin liposomes, the extracts inhibited hexanal formation in the order: sweet cherries > blueberries > red raspberries > blackberries > strawberries. Red raspberries were more efficient than blueberries in inhibiting hydroperoxide formation in lecithin liposomes. HPLC analyses showed high anthocyanin content in blackberries, hydroxycinnamic acid in blueberries and sweet cherries, flavonol in blueberries, and flavan-3-ol in red raspberries. The antioxidant activity for LDL was associated directly with anthocyanins and indirectly with flavo...

HPLC method for screening of flavonoids and phenolic acids in berries

An HPLC method is described for the simultaneous detection of selected flavonoids (kaempferol, quercetin, myricetin) and phenolic acids (p-coumaric, caffeic, ferulic, p-hydroxybenzoic, gallic and ellagic acids) in berries. Three extraction and hydrolysis methods and three HPLC column and solvent systems were tested for strawberry and blackcurrant. The optimal extraction and hydrolysis of these phenolics was obtained by incubating freeze-dried berry samples for 16 h at 35°C in 50% methanol and 1·2 M HCl. The best separation of the hydrolysed phenolics was achieved in ODS-Hypersil column using a ternary solvent system (dihydrogen ammonium phosphate, orthophosphoric acid and acetonitrile) with increasing hydrophobicity and changing pH. The method was used for the determination of the phenolic profiles of strawberry and blackcurrant. The relative content of flavonoids was low in strawberry but over 50% in blackcurrant. Ellagic acid was the main phenolic in strawberry while its relative content was very low in blackcurrant. Although the precision of the method was not equally good for all the phenolics, a reasonable amount of information was obtained within a single analysis. This simple, semiquantitative method is suitable for routine screening of the major phenolics in berries. © 1998 SCI.

Effects of Exogenous Factors on Phenylalanine Ammonia-Lyase Activity and Accumulation of Anthocyanins and Total Phenolics in Grape Berries

The effects of ethephon (E), sucrose (S), and light (L) on phenylalanine ammonia-lyase (PAL) activity and on the concentration of anthocyanins and total phenolics in the berry skins of <i>Vitis vinifera</i> L. Cardinal berries were studied at temperatures of 14°, 22°, and 35°C over a period of 72 hours. Maximum PAL activity was obtained in the light/ethephon/sucrose-treated (LES) and light/sucrose-treated (LS) berries at 36 and 48 hours. In berries kept in the dark, PAL activity decreased over the experimental period. Anthocyanin concentration increased rapidly after a phase of slow accumulation of 24 to 60 hours, depending on the temperature, in the presence of light but not in the dark. Sucrose plus ethephon had a synergistic effect on synthesis of anthocyanins at 22°C. The period of slow anthocyanin accumulation was shortened as temperature increased. Cycloheximide (CHI) applied to LES-treated berries at 22°C caused a significant reduction in the concentration of anthocyanins in berry skins. Rapid phenolic accumulation in grape berry skins occurred after 48 hours at all temperatures. The pattern of changes in total phenolics in berry skins was similar for all temperature treatments with the maximum concentration reached after 60 hours. There were no consistent effects of sucrose and ethephon on total phenol accumulation in berry skins.