title: Electrochemical versus spectrophotometric assessment of antioxidant activity of hop (Humulus lupulus L.) products and individual compounds.
abstract: Antioxidant (AO) activity of extracts of hop cones (Serbian domestic varieties) and commercial hop products (Saaz, Spalter, Spalter select, and Magnum pellets) was determined by parallel application of recently developed direct current (DC) polarographic and widely used DPPH assay. Correlations between 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) scavenging and total phenolics (TPC) determined by the Folin-Ciocalteu assay (FC) (0.99), and between H2O2 scavenging (HPS) and humulone content (H) determined by conductometric method (0.94), total resins (TR) (0.85), and hop storage index (HIS) (-0.90), were found statistically significant at p < 0.05 level while complete lack of HPS correlation with TPC and DPPH was observed. To obtain an insight into differences between results of AO assays applied, activity of individual compounds, prevalent hop phenolics, and bitter acids was determined. By far superior HPS activity of humulone was followed by catechin, quercetin, xanthohumol, lupulone, and rutin. In contrast, DPPH scavenging activity of phenolics (quercetin > catechin > rutin > xantohumol) was found substantially higher than activity of bitter acids. According to ferric reducing antioxidant power (FRAP) and scavenging of 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS), higher AO activity was ascribed to phenolics, while almost neglecting humulone. Besides reliability, low cost, and an easy-to-handle procedure, an ability to recognize humulone as the major contributor of hop AO activity could allow DC polarographic assay to be applied in analysis of various hop-derived products.
authors: Institute of General and Physical Chemistry, University of Belgrade , P.O. Box 45, 11158 Belgrade 118, Serbia.
authors: Stanislava
authors: S
authors: Gorjanović
authors: Ferenc T
authors: FT
authors: Pastor
authors: Radica
authors: R
authors: Vasić
authors: Miroslav
authors: M
authors: Novaković
authors: Mladen
authors: M
authors: Simonović
authors: Sonja
authors: S
authors: Milić
authors: Desanka
authors: D
authors: Sužnjević
mesh_terms: D000975:Antioxidants / Q000032:analysis*; D055664:Electrochemical Techniques / Q000379:methods*; D027582:Humulus / Q000737:chemistry*; D010936:Plant Extracts / Q000032:analysis*; D013053:Spectrophotometry / Q000379:methods*
chemical_list: D000975:Antioxidants; D010936:Plant Extracts