Polymethoxylated, C- and O-glycosyl flavonoids in tangelo (Citrus reticulata × Citrus paradisi) juice and their influence on antioxidant properties

• Eleven flavonoids were identified and quantified by SRM in tangelo juice in a single chromatographic course.
• Two C-glycosyl flavones and one O-triglycosyl flavanone have been identified for the first time.
• Antioxidant assays showed that flavonoids contribute significantly to the total antioxidant activity of crude tangelo juice.
• Analysis of antimicrobial activity showed that tangelo flavonoids are able to inhibit Staphylococcus aureus growth.

A separation/identification protocol based on RP-LC-DAD–ESI-MS–MS has been employed for the characterisation of the flavonoid fraction of the juice from tangelos (Citrus reticulata × Citrus paradisi) grown in Southern Italy. Eleven compounds were identified in a single chromatographic course. Of these, two C-glycosyl flavones (lucenin-2 and vicenin-2) and an O-triglycosyl flavanone (narirutin 4′-O-glucoside) were identified for the first time. Fruit juice antioxidant activity was evaluated on the basis of its ability to scavenge DPPH, O2−, OH and ABTS+ radicals, and to reduce iron (FRAP). Moreover, the influence of the identified polymethoxylated, C- and O-glycosyl flavonoids on the total antioxidant activity has been elucidated. We also checked the antimicrobial activity of a broad fraction, containing all the detected flavonoids obtained by preparative HPLC, in terms of MICs for Staphylococcus aureus.