Chemical composition and antioxidant-prooxidant potential of a polyphenolic extract and a proanthocyanidin-rich fraction of apple skin

Abstract

The apple is a food rich in diverse classes of polyphenols (PP), among which the proanthocyanidins (PCs), which are primarily concentrated in the skin, are one of the most abundant. These compounds are of considerable interest for their possible positive health effects because of their antioxidant properties. However, depending on the classes of PP present (chemical composition) and their relative concentrations in the apple skin, their antioxidant effects vary and some of their components can even generate prooxidant effects. This work determined the chemical composition and antioxidant-prooxidant potential of a polyphenolic extract (PPE) and a proanthocyanidin-rich fraction (PRF) of apple skin, along with the contribution of their most abundant individual compounds, based on their copper chelating ability, ease in reducing peroxidase-generated free radicals and TEAC (Trolox-Equivalent Antioxidant Capacity) assay. For this purpose, chromatographic and colorimetric methods were used. The majority compounds identified in PPE were flavan-3-ols (44.58%), flavonols (42.89%) and dihydrochalcones (11.60%). In PRF, we detected monomers and oligomers from dimers to heptamers, which were composed of 97% (−)-epicatechin and 3% (+)-catechin. The antioxidant potential was notably higher in PRF than in PPE. The (−)-epicatechin monomer and the procyanidin B2 dimer showed more ease in reducing peroxidase-generated free radicals compared to other compounds of the apple skin, whereas phloridzin dihydrochalcone produced prooxidant effects.

Nutritional Composition, Total Phenolic Content, Antioxidant and α-Amylase Inhibitory Activities of Different Fractions of Selected Wild Edible Plants

“…On the other hand, our observed content was lower than some reported Asian vegetables [7,34]. However, it is well recognized that several factors, such as species, plant tissue, temperature, water stress and light conditions, as well as phenological development, can influence the TPC in the plants [22,24,35]. Thus, this explains the large differences observed between our and previous findings.…”

“…Plants rich in secondary metabolites including phenolics and flavonoids demonstrate powerful antioxidant properties, both in vitro and in vivo, which is attributed to their redox properties and chemical structures [35,36,37]. The results of the previous studies are also similar to ours [28,30,31,32,33,38].…”

Efficacy, Stability, and Safety Evaluation of New Polyphenolic Xanthones Towards Identification of Bioactive Compounds to Fight Skin Photoaging

“…In the same way as other catechol containing polyphenols [ 35 ], 1,2-DHX ( 1 ) did not generate prooxidant effects, which are usually associated with the presence of one phenol group on the aromatic ring, since the derived phenoxyl radicals tend to be very unstable.…”

“…Solvents were evaporated using a rotary evaporator under reduced pressure, Buchi Waterchath B-480 (BÜCHI Labortechnik AG, Switzerland). The reaction was monitored by TLC carried out on precoated plates with 0.2 mm thickness using Merck (Darmstadt, Germany) silica gel 60 (GF254) with In the same way as other catechol containing polyphenols [35], 1,2-DHX (1) did not generate prooxidant effects, which are usually associated with the presence of one phenol group on the aromatic ring, since the derived phenoxyl radicals tend to be very unstable.…”

Effect of Constituent Units, Type of Interflavan Bond, and Conformation on the Antioxidant Properties of Procyanidin Dimers: A Computational Outlook

“…, and PB8 [(+)-catechin-(C4 →C6)-(−)-epicatechin], are less frequent in foods but are important components of fruits and cereals of high commercial value, among these grape, apple, and barley, as well as derived beverages, such as juice, red wine, and beer [7][8][9]. Together, these dimers afford contrasting structural characteristics related to the type of constituent units, type of interflavan bond, and conformation, whose study could provide insights concerning the role of molecular structure of PCs on their antioxidant properties.…”