Identification of anthocyanins in muscadine grapes with HPLC-ESI-MS

Muscadine grapes are important fruits grown in the southeastern United States. They are a good source of anthocyanins, but confirmatory analyses of the structure of individual anthocyanins in muscadine grapes using more advanced instrument are lacking. In this study, the anthocyanins of muscadine grapes were analyzed using HPLC-MS with electrospray ionization. Approximately 90% of the total anthocyanins were 3,5-diglucoside of delphinidin, cyanidin and petunidin; the remaining 10% were 3,5-diglucoside of peonidin and malvidin. There was a significant difference of total anthocyanin content among different cultivars of muscadine grapes with purple-skinned muscadine grapes having significantly higher levels of anthocyanins than bronze-skinned muscadine grapes. The total anthocyanin content in purple-skinned Jumbo and Cowart muscadine was 4.1 and 2.6 mg/g dry weight, respectively, while the total anthocyanin content in bronze-skinned Higgin and Carlos was negligible. The anthocyanins were mainly concentrated in the skin of the grapes. The results of the present study confirmed some of the anthocyanins reported by previous studies and also found one anthocyanin that might be falsely identified by previous studies.