The aim of this study was to establish a novel method to assess the function of food components using fluorescently labeling strategies. In this report, we focused on olive polyphenol hydroxytyrosol (HT) as a target of fluorescent labelling. HT, one of the major polyphenols present in olive leaf and oil, is known to possess a high antioxidant and anticancer capacity. HT was conjugated with FITC to the phenolic hydroxyl group (FITC-HT). Caco-2 cells were cultured on glass bottom dishes, and then incubated with 500 μm of FITC-HT for 24 hours and subsequently incubated with LysoTracker Red (Lysosome marker) or MitoTracker Red (Mitochondria marker) with Hoechst 33342 (Nuclei marker). Thereafter, using KEYENCE BZ-X700 Series All-in-one Fluorescence Microscope, the imaging data was acquired. As a result, FITC-HT was detected in the lysosome but not in the mitochondria and nuclei of Caco-2. And, FITC and fluorescein were not detected in the Caco-2 cells, suggested this imaging data of FITC-HT is dependent on the formula of HT. Thereafter, we concluded that cellular imaging using fluorescent labeled food compounds is a powerful tool to analyze the effect of functional food constituents.
