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.