Flavonoid Profiles in the Pulp of Different Lemon Cultivars and Their Antioxidant Activity Based on UPLC–Q–TOF–MS

Previous studies have indicated that there may be differences among the varieties of lemon flavonoids, but the details have not yet been made clear, which limits the comprehensive use of different cultivated lemon varieties. In this study, ultra-performance liquid chromatography–quadrupole–time-of-flight–mass spectrometry (UPLC–Q–TOF–MS) and ultraviolet–visible spectroscopy (UV–Vis) were used to investigate the types and contents of flavonoids in the flesh of the main cultivated variety (Eureka) and five common lemon varieties, as well as their in vitro antioxidant activity. A total of 21 compounds were identified, five of which were common compounds. Among them, Verna, Lisbon, and Bearss each have characteristic components that can serve as potential criteria for variety identification. Each of the six varieties of lemon has strong antioxidant activity. The antioxidant activity of different lemon varieties is related to flavonoids. Therefore, Eureka and the other five varieties of lemon are good natural antioxidants, and the cultivation and industrial production of lemons should consider the needs and selection of suitable varieties.