Flavonoid Composition of Tarocco (Citrus sinensis L. Osbeck) Clone “Lempso” and Fast Antioxidant Activity Screening by DPPH-UHPLC-PDA-IT-TOF

Introduction: Clonal selection and hybridisation are valid strategies to obtain fruits with enhanced sensorial and nutraceutical properties. Within Citrus sinensis varieties, Tarocco clone “Lempso” is a typical product of the Calabria region (Italy) characterised by its red pulp. This is the first report concerning its accurate profiling. Objective: To characterise in detail the flavonoid composition of Lempso clone and to compare its antioxidant potential with other Citrus varieties by a fast screening method. Methodology: Extracts were subjected to solid phase extraction and the qualitative/quantitative profile was elucidated through ultra-high performance liquid chromatography (UHPLC) coupled to photodiode array (PDA) and ion trap time-of-flight (IT-TOF) mass spectrometry detection, and compared to both Cleopatra mandarin (Citrus reticulata) and blood orange (Citrus sinensis (L.) Osbeck) Sanguinello varieties. The antioxidant activity was assessed by pre-column 2,2′-diphenyl-1-picrylhydrazyl (DPPH) reaction coupled to UHPLC-PDA. Results: Lempso is characterised by flavonoids (17) and anthocyanins (8). Flavanones content (Hesperidin: 57.19 ± 0.49, Vicenin-2: 4.59 ± 0.03, Narirutin: 5.78 ± 0.13 mg/100 mL) was considerably higher than Cleopatra and Sanguinello varieties. The developed DPPH-UHPLC-PDA method provides information regarding the single contributions to antioxidant activity, highlighting how Ferulic acid, Quercetin and Cyanidin derivatives possess considerable radical scavenging activity (> 50%). The total antioxidant activity was also evaluated and compared with positive controls, showing higher scavenging activity than Cleopatra and Sanguinello (IC50: 333.76 ± 10.81 μg/mL vs. 452.62 ± 10.81 and 568.39 ± 26.98 μg/mL, respectively).