Examining the Performance of Two Extraction Solvent Systems on Phenolic Constituents from U.S. Southeastern Blackberries.

Two common extraction solvent systems, namely acidified aqueous methanol and acidified aqueous acetone, were used to extract blackberry phenolics, and the antioxidant properties of the recovered extracts were compared. The crude extracts were fractionated into low- and high-molecular-weight phenolics by Sephadex LH-20 column chromatography. The hydrophilic-oxygen radical absorbance capacity (H-ORACFL), ferric reducing antioxidant power (FRAP), and the cellular antioxidant activity (CAA) assays were employed as indices to assess antioxidant capacity of the extracts and their respective fractions. The methanolic solvent system displayed a greater efficiency at extracting anthocyanin and flavonol constituents from the blackberries, while the acetonic solvent system was better at extracting flavan-3-ols and tannins. Anthocyanins were the dominant phenolic class found in the blackberries with 138.7 ± 9.8 mg C3G eq./100 g f.w. when using methanol as the extractant and 114.6 ± 3.4 mg C3G eq./100 g f.w. when using acetone. In terms of overall antioxidant capacity of blackberry phenolics, the acetonic solvent system was superior. Though present only as a small percentage of the total phenolics in each crude extract, the flavan-3-ols (42.37 ± 2.44 and 51.44 ± 3.15 mg/100 g f.w. in MLF and ALF, respectively) and ellagitannins (5.15 ± 0.78 and 9.31 ± 0.63 mg/100 g f.w. in MHF and AHF, respectively) appear to account for the differences in the observed antioxidant activity between the two solvent systems.

The cellular antioxidant and anti-glycation capacities of phenolics from Georgia peaches.

Plant-based polyphenolics have been reported to bestow health benefits when consumed, which are partially ascribed to their antioxidant activity. Yet, many current in vitro chemical assays to characterize antioxidant potential do not truly reflect the physiological properties of food antioxidants in vivo. The present study employed biological approaches, including a cellular antioxidant activity (CAA) and protein glycation assays, to offer an improved picture of antioxidant potential of phenolic extracts from Georgia peach cultivars. The phenolic extracts from two peach varieties, showing contrasting antioxidant capacities according to hydrophilic-oxygen radical absorbance capacity (H-ORACFL) and ferric reducing antioxidant power (FRAP) assays, exhibited significant differences in two biological tests when the assays were performed on a fresh weight basis. The procyanidins fraction displayed notable antioxidant capacity, when compared to other phenolic classes in the peach extract, in these two biologically relevant assays.

Characterizing the phenolic constituents and antioxidant capacity of Georgia peaches.

Acetonic crude phenolic extracts of six Georgia peach cultivars were prepared and separated into low- and high-molecular-weight (LMW and HMW) fractions by Sephadex LH-20 column chromatography. Further characterization via RP-HPLC-ESI-MS identified the main phenolics as hydroxycinnamates, (+)-catechin, and proanthocyanidins with degrees of polymerization up to seven. The LMW phenolics of the commercial cultivar, 'July Prince', were further chromatographed and examined by RP-HPLC-ESI-MS. Derivatives of phenolic acids and flavan-3-ols, along with eriodictyol and quercetin diglycosides, were identified. Antioxidant capacities of the LMW and HMW fractions were determined using in vitro assays. H-ORACFL and FRAP assays gave values of 872 to 2428 µmol Trolox eq./100 g f.w. and 309 to 432 µmol Fe2+ eq./100 g f.w., respectively. The total phenolics content (TPC) was also measured; correlations between TPCs and antioxidant assays indicated that the HMW fractions of peach extracts were major contributors to the antioxidant capacity of the cultivars analyzed.