Vitamin C Equivalent Antioxidant Capacity (VCEAC) of Phenolic Phytochemicals

Abstract

To express the antioxidant capacity of plant foods in a more familiar and easily understood manner (equivalent to vitamin C mg/100 g), two stable radical species, ABTS(*)(-) and DPPH(*), commonly used for antioxidant activity measurements, were employed independently to evaluate their efficacies using apple polyphenolic extracts and seven polyphenolic standards including synthetic Trolox. Their antioxidant activities were expressed as vitamin C equivalent antioxidant capacity (VCEAC) in mg/100 g apple or mg/100 mL of the reference chemical compounds in 10 and 30 min using the ABTS(*)(-) and DPPH(*) scavenging assays, respectively. The antioxidant capacity of Gala apples and seven phenolic standards, determined by both ABTS(*)(-) and DPPH(*) scavenging assays, showed a dose-response of the first-order. Fresh Gala apples had a VCEAC of 205.4 +/- 5.6 mg/100 g using the ABTS assay, and the relative VCEACs of phenolic standards were as follows: gallic acid > quercetin > epicatechin > catechin > vitamin C > rutin > chlorogenic acid > Trolox. With the DPPH radical assay, the VCEAC of fresh Gala apples was 136.0 +/- 6.6 mg/100 g, and the relative VCEACs of seven phenolic standards were, in decreasing order, as follows: gallic acid > quercetin > epicatechin > catechin > or = vitamin C > Trolox > rutin > chlorogenic acid. Because the ABTS assay can be used in both organic and aqueous solvent systems, employs a specific absorbance at a wavelength remote from the visible region, and requires a short reaction time, it is a more desirable method than the DPPH assay. Therefore, it is recommended that antioxidant capacity be expressed as vitamin C mg/100 g equivalent (VCEAC) using the ABTS assay.

Plum pomaces as a potential source of dietary fibre: composition and antioxidant properties

“…Sum of proanthocyanidins was measured according to method described by Nakamura et al (2003). Antioxidant activity was measured by DPPH method and calculated as Trolox equivalent (TEAC) (Kim et al 2002). Composition of sugars was determined by HPLC as described previously (Kołodziejczyk et al 2009).…”

Comparison of the phenolic content and total antioxidant activity in wines as determined by spectrophotometric methods

“…The working solution was prepared by dilution of methanolic DPPH • solution (98 mg/l, absorbance ≈ 1.9) to the absorbance of ≈ 1.5 AU (the same for the sample and standard) to provide a sufficient reaction capacity for higher contents of antioxidants in the extracts. A portion (950 μl) of the working solution and the sample of wines (50 μl; red wines diluted 5 to 10-fold) or standard were adjusted to 1000 μl with aqueous methanol (1:1, v/v) and incubated 30 minutes to reach plateau (Kim et al 2002). The absorbance was read at 515 nm against blank (aqueous methanol).…”

The roles of polyphenols in cancer chemoprevention

“…Quercetin (3,3',4',5,7-pentahydroxyflavone) is a major antioxidative flavonol present in apple [62] and onion [98] that exhibits significant inhibitory activity against lipid peroxidation induced by tert-butyl hydroperoxide in rat hepatocytes [89] and scavenging activity against 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) and 2,2-diphenyl-1-picrylhydrazyl radicals [46]. The strong antioxidant activity of quercetin appears to be attributable to the presence of an orthocatechol group (3',4'-OH) in the Bring [104].…”