Abstract: Ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS) based metabolomics was used to analyze the relationship between the varieties and contents of flavonoids and color change during the fruit development of jujube (cv. Sanbianhong). Results showed that as fruit development proceeded from S1 to S2 to S3, the color changed from purple red to green white to deep red, and the total flavonoid content of jujube peel showed an increase-decrease-increase trend, which was 4.94, 0.95 and 4.45 mg/g dry at mass at the three time points, respectively, indicating that the content of total flavonoids in jujube peel was positively correlated with the color change. Principal component analysis (PCA) and orthogonal partial least square-discriminate analysis (OPLS-DA) showed clear differences in the composition and contents of flavonoids at the three developmental times. The contents of quercetin 3-O-rutinoside, methyl quercetin O-hexoside, luteolin O-sinapoylhexoside, luteolin O-sinyl hexoglucoside, naringenin O-malonylhexoside, 3,4,5-trihydroxyflavone O-rutinoside, 6-C-hexosyl-luteolin O-hexoside and isovitexin at S1 were much higher than those at S2 and S3, and they were identified as characteristic flavonoids at the S1 stage, while cyanidin O-hexose, apigenin O-hexosyl-pentoside, quercetin 5-O-malonylhexosyl-hexoside, sirolimus O-glucuronoic acid (salicyl alcohol) ether O-dialuronic acid, and chrysoeriol were considered as characteristic flavonoids at the S3 stage. This study is of great significance to reveal the mechanism of fruit coloration in “Sanbianhong” jujube.

Key words: “Sanbianhong” jujube fruit; characteristic flavonoids; ultra-high performance liquid chromatography-mass spectrometry; cluster analysis