Antioxidant Capacity and Polyphenol Compounds Characterization Through LC-ESI-QTOF-MS/MS in Citrus Peels From Different Varieties

Abstract

Citrus peel, a waste product of fruit processing industries, is an abundant source of polyphenols with strong antioxidant capacity. This study aimed to investigate the antioxidant potential of peels from six Victorian-grown citrus varieties through a combination of in vitro antioxidant assays and polyphenol profiling by LC-ESI-QTOF-MS/MS. Peels from Cara Cara Navel variety had the greatest total phenolic content (7.26 mg GAE/g). Peels from Dekopon variety demonstrated the strongest antioxidant capacity in ABTS, DPPH, and FRAP assays. A moderate positive correlation was observed between total flavonoid content and DPPH antioxidant activity (r = 0.61), while it had a high positive correlation (r = 0.71) with FRAP. A tentative characterization of polyphenolic compounds using LC-ESI-QTOF-MS/MS analysis identified 55 phenolic compounds within the citrus peels, with flavonoids representing the predominant class. Our findings demonstrated the significant antioxidant capacity and polyphenolic compounds in these citrus peel samples, in particular Dekopon variety. These findings provide the first detailed characterization of polyphenolic diversity across Victorian citrus peels and highlight their potential as a source of bioactive compounds. The observed varietal differences and significant antioxidant properties provide a foundation for valorization of citrus peel waste for utilization in food preservation or nutraceutical development, thereby supporting a broader circular economy.