Polyphenolic compounds in apple (Malus domestica Borkh.) cultivars grown in Estonia

Abstract

Several studies have shown that apples (Malus domestica Borkh.) in the daily diet are healthy due to their rich content of phytochemicals. The aim of this study was to compare the content of polyphenols in the peels, flesh, seeds and leaves of five apple cultivars (‘Antonovka’, ‘à kerö’, ‘Cortland’, ‘Karksi renett’ and ‘Krista’) grown in Estonia. Of the 21 collected cultivars, these five were selected on the basis of their rich or distinct chemical composition according to the LC-DAD-MS/MS data. In addition, the weight of the fruit, the number of seeds in the fruit and the weight of the seeds were determined. A total of 33 compounds were detected in the peels, 23 in the flesh, 11 in the seeds, and 25 in the leaves. They belong to four groups: 1) flavon-3-ols (quercetin and its derivatives), 2) dihydrochalcones (phloretin and its derivatives), 3) flavan-3-ols (catechin, epicatechin and oligomers), and 4) esters formed between caffeic acid and L-quinic acid (chlorogenic acid). Based on the data presented in this article, the leaves contained the highest measured total polyphenol content (TPGA). The peels contained high amounts of all the major polyphenolic groups mentioned. The apple flesh lacked flavon-3-ols and the seeds flavon-3-ols and flavan-3-ols. In the peels, the major polyphenols were quercetin galactoside (3–342 mg/100 g), procyanidin B1 (18–179 mg/100 g), and (epi)catechin trimer (28–200 mg/100 g); in the flesh chlorogenic acid (77–298 mg/100 g); in the seeds phloridzin (466 mg/100 g in ‘Cortland’); and in the leaves chlorogenic acid (147–446 mg/100 g) and quercetin glycosides, especially quercetin rhamnoside (242–350 mg/100 g), quercetin galactoside (39–334 mg/100 g) and quercetin glucoside (91–321 mg/100 g).

Keywords

• apple
• flesh
• ‘karksi renett’
• ‘krista’
• leaves
• peel
• seeds.