Bio imaging of Citrus Flavones and pesticides in fresh orange

Sweet orange (Citrus sinensis Osbeck) is highly consumed fruit throughout the world. It has been consumed not only for the edible flesh but also for the thick bitter peels for the source of foods, drugs and cosmetics. Its major constituents include flavonoids, mainly polymethoxylated flavonoids, and terpenoids, including limonene and linalool. Major concern in utilizing this bio-functional part of orange is possible exposure to high concentration of pesticides. In order to analyze the distribution of bio-active flavonoids and pesticide from outer orange peel (flavedo) to its inner skin (alvedo) simultaneously, direct analysis in real time-time of flight-mass spectrometry (DART-TOF-MS) was utilized. Mass spectrometry imaging is an efficient way to show the distribution of metabolites in various tissues. In this study, we analyzed the distribution of polymethoxyflavones (tetra, penta, hexa, heptamethoxyflavone), limonene, and pesticides (imazalil, thiabendazole) in orange by using DART-TOF-MS. This method allowed to obtain images related to flavonied and pesticide concentration in the outer and inner peel of oranges. The flavonoids and the pesticides are mainly located in outer peels. DART-TOF-MS analysis and mass spectrometry imaging for local distribution of target compounds on natural resources can be applied as a key tool for efficient monitoring to secure safety and quality.

Keywords: DART-imaging