Comparative HPLC-DAD-ESI-QTOF-HR-MS/MS analyses of phenolic compounds of authentic lemon, lime, orange, and grapefruit juices

Detailed knowledge about phenolic compounds of Citrus fruits and derived juices is important for investigations into Citrus product authentication as well as for their potential health benefits. We present an HPLC-DAD-ESI-QTOF-HR-MS/MS method for the identification and simultaneous quantitation of more than 50 compounds ranging from polar phenolic acids over flavonoid glycosides to apolar coumarins, psoralens, and polymethoxyflavones in lemon, lime, orange, and grapefruit juices. Hydroxycinnamic acid derivatives mainly comprised esters with aldaric acids, N-p-coumaroylputrescine, and N-feruloylputrescine. Predominant flavonoids were flavone-C- and O-glycosides, flavonol- and flavanone-O-glycosides, and polymethoxyflavones. Mass fragmentations of flavone-C- and O-glycosides as well as limocitrin glycosides and their acylated derivatives carrying malonyl- and/or hydroxymethylglutaryl moieties are proposed. The presence of diverse phenolic compounds in juices from four Citrus species was confirmed and numerous novel constituents were assigned. Total levels of phenolic constituents in the aforementioned Citrus juices are presented.