Apple polyphenols

Polyphenols are one of the most important dietary antioxidants, and apple is a major source of phenol compounds, since its consumption is widespread in many countries and it is available on the market for the whole year. It has been reported that 22% of the fruit phenolics consumed in the United States is from apples.

Apples represent an important source of bio-available phenolic compounds, such as flavonols (with quercetin glycosides as the main component), monomeric and oligomeric flavanols, dihydrochalcones (e.g., phloridzin), anthocyanidins, p-hydroxycinnamic, and p-hydroxybenzoic acids. The content of phenolic compounds varies greatly among apple varieties as well as its peel and flesh, with apple peel containing a higher concentration of phenolic compounds than the flesh.

The phenolic composition of apples, and thus their antioxidant activity, is deeply influenced by their variety and can be modified by postharvest factors, including storage and processing.

In general, the polyphenolic contents per fruit ranges between 19.6 and 55.8 (flavan-3-ols), 17.7–33.1 (flavonols), and 10.6–80.3 (chlorogenic acid) mg per apple; the lowest values were recorded for phloridzin (1.0–9.3 mg per apple) and anthocyanin (0.1–6.5 mg per apple).

Apple peel and the flesh are significant sources of polyphenols and the polyphenol composition is unique in both peel as well as flesh. For example, flavonol glycosides are exclusively located in the peel and hydroxycinnamic acids are mostly found in the flesh.

The highest concentrations of dihydrochalcones (e.g phlotein-2-xyloglucosde) occurred in the core zone, the lowest concentrations were found in the parenchyma. The highest amounts of flava-3-ols were detected in the peel and the core zones. In total, 30-36% of the polyphenolic compounds were found in the parenchyma zone, 17-48% in the peel zone and 11-28% in the core zone.

Apples fruit, as well apple juice and other derivate products, have a rich phytochemical profile suggesting their potential to affect the health of the populations consuming them.
Apple polyphenols