LC/MS-Based Metabolomic Analysis of Peels from Citrus Varieties

Abstract

Many new citrus varieties are developed to improve their quality, but the chemical profiles of their peels are rarely investigated. In this study, the peel metabolite profiles of 13 citrus varieties were analyzed using ultra-performance liquid chromatography-quadruple time-of-flight mass spectrometry (UPLC-Q-TOF MS) and their correlation with antioxidant activity was evaluated. Among the citrus peel metabolites, 30 flavonoids, including polymethoxyflavone (PMF), and vitamin C were identified. These flavonoids contributed to the difference between the 13 citrus peels, and their relative contents varied with each variety. Hesperidin, sinestin, nobiletin, tetramethoxyflavone derivatives, and tangeretin were identified as the major flavonoids in citrus peel, while rhoifolin, margaritene, isomargaritene, catharitcin, and fortunellin were detected only in Changshou kumquat. The correlation data between the metabolite profile and antioxidant activity indicated that didymin and some polymethoxyflavones had a positive correlation with antioxidant activity, while the flavonoids in Changshou kumquat had a negative correlation. Based on these data, the 13 citrus varieties were clustered into three groups: Changshou kumquat (cluster Ⅰ), Setoka and Kanpei (cluster Ⅱ), and other varieties (cluster Ⅲ). These results provide information on peel metabolites and their distribution according to citrus varieties. However, further studies on the beneficial effects of each metabolite and citrus peel are necessary.

Fermentation Characteristics of Unripe Citrus unshiu Vinegar Production Using Acetic Acid Bacteria Isolated from Traditional Fermented Vinegars

“…C. unshiu contains about 60 types of bioactive compounds, including flavonoids, carotenoids, phenylpropanoids, and limonoids ( Lee et al, 2022b ), along with various nutrients (e.g., free sugars, organic acids, dietary fibers, vitamins, and minerals) ( Ahn et al, 2007 ). Consequently, numerous preclinical and clinical trials have reported on the various physiological activities induced by antioxidants in C. unshiu peels and pulp ( Ahn et al, 2007 ; Park et al, 2020 ; Lee et al, 2022a ). In the past, unripe C. unshiu fruits, known as green tangerines, were largely considered to have no industrial value and were often discarded in large quantities ( Yi et al, 2022 ).…”

Chemical profile and antioxidant activity of peel of Yellowball, a novel citrus variety

“…Citrus fruits are rich in bioactive substances that are valuable for disease prevention, including vitamin C, citric acid, flavonoids, carotenoids, and pectin, and they are widely consumed as fresh fruits or as processed fruit products such as juice and jam (Lee et al, 2022). Notably, citrus fruits exhibit significant pharmacological value because they contain about 60 different flavonoids known https://doi.org/10.11002/kjfp.…”

“…Yellowball peel was included in a study of 13 citrus fruit varieties that used metabolite analyses to determine the phytochemical profiles and antioxidant activities of the fruits, and it exhibited significantly strong antioxidant activity. The main compounds in Yellowball were the flavonoid hesperidin, and PMFs such as tangeretin, sinensetin, nobiletin, and tetramethoxyflavone (Lee et al, 2022). However, the number of studies investigating the antioxidant compounds in Yellowball peel is currently insufficient.…”