Phenolic compounds and antioxidant activity in red-fleshed apples

• Difference in phenolic profile is analysed between red- and white-fleshed varieties.
• Three red-fleshed apple varieties from Xinjiang are evaluated for the first time.
• Quantitative analysis is conducted on the individual phenolic compounds.
• Correlations between anthocyanin content and antioxidant activity are discussed.

Red-fleshed apples are receiving increased attention because of their remarkable anthocyanin contents. To provide sufficient experimental evidence about their phenolic composition and strong antioxidant capacity, three red-fleshed varieties from Xinjiang, P.R. China and one from the USA were evaluated. For comparison, two commercial white-fleshed varieties were also included. In samples of the flesh, contents of phenolics (total phenolics, flavonoids, flavanols, and anthocyanins) and antioxidant activity were significantly higher for red-fleshed varieties than for white-fleshed varieties. Flavonoid profiles also differed between the red- and white-fleshed varieties. Among the red-fleshed varieties, ‘Roberts Crab’ had the highest amounts of total phenolics, flavonoids, and anthocyanins, as well as the strongest antioxidant activity, while ‘Xiahongrou’ had the lowest levels of total phenolics and flavonoids and the weakest activity. HPLC analysis revealed that individual phenolic compounds varied significantly among red-fleshed varieties. These results suggest that red-fleshed apples are a promising source of antioxidants for human nutrition.