Mandarin cultivars (Citrus reticulata) represent 22% of the total citrus fruit crops1. Mandarin fruit residues (peel, seeds, and pulp) are usually discarded without regard to potential nutritional and commercial value. Mandarin peels are an abundant source of natural flavonoids2 and other antioxidants. The aim is to determine the polyphenols content and antioxidant capacity from hybrid mandarins peel from Valencia province (Spain). A 33 samples of hybrid mandarins (´Clemenvilla`, ´Nadorcott` and ´Ortanique`), procured by citrus farmers of the province of Valencia (Spain), were selected. Fresh mandarin peel extracts were prepared by ultrasound assisted extraction (400 W, 80% v/v duty cycle, 40 ºC) at 30 min employing ethanol 50% (v/v) as solvent in 1:10 (w/v) solid-liquid ratio. Total polyphenols (TP), and total flavonoids (TF) content were determined by spectrophotometry3 and, 2,2-diphenyl-1-picrylhydryzyl (DPPH) and Trolox equivalent antioxidant capacity (TEAC) assays3,4 were employed to determine the antioxidant capacity. Before the chromatographic analysis, C18 cartridges (200 mg) were employed for the Solid Phase Extraction clean-up process5. A ultra-performance liquid chromatography system coupled with a quadrupole time-of-flight mass spectrometer was used to identify and quantify the main polyphenols in samples. TP and TF content varied according to the mandarin variety (p<0.05). TP was higher in ´Ortanique` samples (1155±171 mg GAE/100 g), while ´Clemenvilla` samples had the highest values of TF (90 ± 16 mg catechin/100 g). ´Clemenvilla` and ´Ortanique` extracts showed the highest antioxidant capacity by DPPH (14±4.8 mmol Trolox/100 g) and TEAC (32±3.8 mmol Trolox/100 g) assays, respectively. The main polyphenol present in samples was hesperidin being higher in ´Nadorcott` peel (72±7.0 µg/g). Narirutin and rutin were higher in ´Ortanique` and ´Clemenvilla` peel (33±6.3 and 7.3±3.8 µg/g, respectively). Analyzed mandarin peels are an important source of polyphenol compounds with high antioxidant capacity. Results suggest that hesperidin, narirutin and rutin are the main polyphenols in hybrid mandarin peel.
