Study on the compositions and contents of phenols in different parts of the fruit of different jujube varieties

Phenol, an important bioactive substance in jujube fruit, is one of the most important indexes of fruit quality. In this study, six jujube varieties, Junzao (JZ), Dongzao (DZ), Pingguozao (PGZ), Fucuimi (FCM), Jinlingyuanzao (JLYZ) and Fengmiguan (FMG), were used as test materials to determine the phenolic substance compositions and total phenolic and total flavonoid contents of different parts of the fruit and to analyze them by high performance liquid chromatography. The results showed that a total of 14 phenolic substances were identified in the jujube fruit, including proanthocyanidins, catechins, epicatechin, chlorogenic acid, rutin, rhizobioside, quercetin, quercitrin, P-hydroxybenzoic acid, quercetin triglycoside kaempferol glycoside, ferulic acid, quercetin rhamnoside and P-coumaric acid.The JLYZ and JZ fruits were found to be rich in phenolic substances, with the highest content of polyphenols in the jujube peel and the lowest content of polyphenols in the external pulp. A comprehensive evaluation of phenolic contents in different jujube varieties and different parts of the fruit was conducted via principal component analysis: JZ received the highest comprehensive score, indicating that it can be used as an excellent variety for functional product development; the score of the peel was much higher than that of the pulp. The scores of different parts of the pulp ranked as follows: internal > lower > middle > upper > external. Therefore, the jujube peel and pulp near the core of the fruit have better development prospects and greater processing and utilization value.