Evaluation of Total Phenols, Flavonoids, and Antioxidant Activity in the Peel and Flesh of Old Apple Cultivars

Apples (Malus domestica Borkh.) are widely cultivated due to their storability, adaptability to diverse climatic conditions, versatility, and affordability. In addition to these agronomic advantages, apples are a significant dietary source of nutrients and bioactive compounds, particularly polyphenols, a major class of phytochemicals with several beneficial health effects. The aim of this study was to quantify and compare the total phenolic and flavonoid contents of peel and flesh of eighteen traditional old apple cultivars from the Banat region of Romania, evaluate their antioxidant activity, and characterize the colour parameters and individual phenolic profiles of two selected cultivars. The results showed considerable variation among cultivars, with ‘Caslere’ and ‘Măr de Jupani’ exhibiting the highest contents of bioactive compounds. Across the 18 cultivars, phenolic contents ranged from 218.17–1497.35 µg gallic acid equivalents (GAE)/g dry matter (DM) in the peel and 323.54–1111.65 µg GAE/g DM in the flesh, while flavonoid contents ranged from 1157.43–4796.05 and 1426.01–3697.16 µg rutin equivalents (RE)/g DM, respectively. Antioxidant activity ranged from 33.55–99.51% in the peel and 44.41–88.88% in the flesh, highlighting pronounced tissue-specific differences in bioactive compound distribution. Positive correlation was found between phenolic content and antioxidant activity. High-performance Liquid Chromatography (HPLC) analysis revealed cultivar-specific phenolic profiles, with rosmarinic acid and resveratrol among the predominant compounds, while epicatechin was particularly abundant in the peel of ‘Caslere’ cultivar. Colour analysis further demonstrated distinct differences between the two cultivars, reflecting variation in peel pigmentation and biochemical composition. These findings highlight the nutritional and functional value of traditional apple cultivars and support their conservation and valorization as valuable genetic resources and sources of health-promoting phytochemicals.