Differentiating\nTangerine Peels from Other Citrus\nreticulata through GC-MS, UPLC-Q-Exactive\nOrbitrap-MS, and HPLC-PDA

The nonvolatile and\nvolatile compounds in the peels of 13 Citrus reticulata cultivars (4 mandarins, 5 tangerines,\nand 4 hybrids) and 5 Citrus sinensis (sweet oranges) cultivars were analyzed. Initially, 66 volatile\ncompounds were detected using gas chromatography–mass spectrometry\n(GC-MS). Tangerines were distinguished from other citrus cultivars\n(mandarins, sweet oranges, hybrids) by having higher volatile oil\nextraction rates and higher relative contents of o-Cymene, α-Terpinene, d-α-Pinene, Terpinolene, γ-Terpinene, l-β-Pinene, and 3-Thujene. Additionally, 115 nonvolatile compounds\nwere tentatively identified using ultraperformance liquid chromatography-Q-Exactive\nOrbitrap tandem mass spectrometry (UPLC-Q-Exactive Orbitrap-MS). C. sinensis contained fewer compounds than did C. reticulata. Pterostilbene was detected in all\ntangerines but not in mandarins and hybrids, suggesting its potential\nas a marker compound for differentiating tangerines from other C. reticulata. Lastly, a high-performance liquid\nchromatography-photodiode array (HPLC-PDA) was used to quantify 9\nmajor nonvolatile components. Heat map and principal component analysis\nshowed that the contents of tangerines differed from other cultivars\n(sweet oranges, mandarins, and hybrids). It may be caused by the higher\ncontent of synephrine, nobiletin, tangeretin, and 5-hydroxy-6,7,8,3′,4′-pentamethoxyflavone\nin tangerines. The study may obtain information for the application\nof different types of C. reticulata (tangerines, mandarins, or hybrids) and C. sinensis peels, thereby promoting their recycling.