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.
This study was focused on in vitro screening of the total antioxidant activity of the selected extracts of the mushroom Coprinus comatus and quinic acid, one of their antidiabetic ingredients, by an uncommon electrochemical assay. Indeed, direct current (DC) polarographic HydroxoPerhydroxo Mercury(II) Complex (HPMC) assay based on decrease of anodic limiting current originating from HPMC formation in alkaline solutions of hydrogen peroxide at potential of mercury dissolution, observed upon gradual addition of antioxidants, was applied herein for the estimation of the natural products' antioxidativity. Quinic acid was found to exhibit most promising antioxidant potential (4.0±0.2 %µL -1 ) being ≈ 2-fold more active than the screened C. comatus extract samples. Actually, such a finding puts some light on the antioxidativity of cyclic polyols, well understimated class of organic compounds, compared to aromatic (poly)phenolics. As a low cost, easy-to handle and accurate this polarographic assay may be thoroughly recommended for much broader use.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.