Analyses of arbutin and chlorogenic acid, the major phenolic constituents in Oriental pear

The HPLC retention time, photodiode array UV spectrum analysis, and LC/MS results indicated that arbutin and chlorogenic acid are the main phenolic constituents in Oriental pear. The two compounds exist in different organs of the Yali pear, which is one of the major cultivars of Pyrus bretschnrideri. The contents of arbutin in the leaf bud, floral bud, flower, and young fruit were 11.9, 12.4, 8.29, and 9.92 mg/g fresh weight (FW), respectively. Chlorogenic acid amounts in the same organs were 2.26, 3.22, 5.32, and 3.72 mg/g FW, respectively. During development, the concentration of the two compounds in Yali pears was the greatest in young fruit (9.92 mg/g FW of arbutin and 3.72 mg/g FW of chlorogenic acid), and then declined swiftly with fruit growth to less than 0.400 and 0.226 mg/g FW, respectively, in mature fruit. Large differences existed in the distribution of the two compounds in parts of the mature fruit of 14 Oriental pear cultivars. The greatest concentration of arbutin was found in the peel (1.20 mg/g FW), which was 3-5 times greater than that found in the core and 10-45 times greater than the level in the pulp. The concentration of chlorogenic acid in the core was greater than that in the peel. The compounds in 17 cultivars of Oriental pear, including P. bretschnrideri, Pyrus pyrifolia, Pyrus ussuriensis, and Pyrus sinkiangensis, were compared with those in 5 cultivars of Occidental pear (Pyrus communis). The mean concentration of arbutin in the Oriental pear cultivars was 0.164 mg/g FW, greater than the 0.083 mg/g FW found in the Occidental pear cultivars. The greatest arbutin content was 0.400 mg/g FW, found in the Yali pear. However, the mean concentration of chlorogenic acid in the Oriental pear was 0.163 mg/g FW, less than that found in the Occidental pear (0.309 mg/g FW).