Abstract: In order to better understand the changes in the phenolic composition and antioxidant capacity of pear fruit from three major cultivars grown in Xinjiang during its development, the contents of total phenolics, total flavonoids and?individual phenolics in developing pear fruit from the cultivars ‘Korla fragrant’, ‘Zaosu’ and ‘Xinli 7’ (‘Korla fragrant’ × ‘Zaosu’ hybrid) were determined, and the 1,1-diphenyl-2-picrylhydrazyl (DPPH)- and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) cation radical-scavenging capacity were evaluated. The results showed that for all cultivars, the contents of total phenols and total flavonoids and DPPH radical-scavenging capacity exhibited an overall decreasing trend during the whole development process, while the ABTS cation radical-scavenging capacity initially decreased, then increased and finally decreased again. On day 50 after flowering, the highest contents of total phenols and total flavonoids and DPPH free radical-scavenging capacity (23.10, 32.25 mg/g and 29.12 μmol/g, respectively) were recorded in ‘Zaosu’ pears, as well as the highest ABTS cation radical-scavenging capacity of 80.74 μmol/g on day 80 after flowering. Significant differences among pear fruits from the same cultivar at different development stages were found in the contents of phenolics (P < 0.05), and the contents of arbutin, catechin, chlorogenic acid, epicatechin, antioxidant glycosidase and kaempferol-3-O-glucoside were gradually reduced. The content of arbutin was the highest, with an average of 5 797.82 μg/g, followed by chlorogenic acid, with an average of 1 781.02 μg/g. The contents of total flavonoids, total phenols, arbutin, catechin, chlorogenic acid and epicatechin in pear fruit were significantly positively correlated with DPPH radical-scavenging capacity (P < 0.01). In short, the phenolic contents and antioxidant capacity of the three pear cultivars at the young fruit stage (50 days after flowering) were higher, and the contents of total phenols and total flavonoids as well as DPPH and ABTS radical-scavenging capacity were higher in ‘Zaosu’ pears than in the other cultivars.

Key words: ‘Korla fragrant’ pears; ‘Zaosu’ pears; ‘Xinli 7’ pear; growth stages; antioxidant capacity; phenolic substances