ABSORPTION AND TRANSPORT OF FLUORINE FROM DIFFERENT TEAS IN A Caco-2 CELL MODEL

This paper aimed to clarify the absorption and transport of fluorine from different fermented teas in a Caco-2 cell model. Chemical composition analysis showed that tea polyphenols and catech ins were the highest in green tea water extract (GE) and the lowest in dark tea water extract (DE), while the fluorine content was the lowest in GE and the highest in DE. The water extracts of green tea, black tea (BE), and dark tea were shown to vary significantly in their effects on the proliferation of Caco-2 cells, with IC50 values of 624.6 mu g/mL, 710.5 mu g/mL, and 1258.8 mu g/mL for them, respectively, which were significantly higher than that of sodium fluoride (NaF, IC50 67.2 mu g/mL) and suggest that DE has the lowest inhibitory activity and least toxicity to Caco-2 cells. Meanwhile, DE was significantly lower than GE or NaF and exhibited no difference from BE in the fluorine positive transport amount and apparent permeability coefficient (P-app) in the Caco-2 cell model, indicating the least fluorine bioavailability for DE. The fluorine P-ratio(P-app(BL-AP)/P-app(AP-BL)) for the three tea extracts showed an upward trend with increasing treatment time and concentration and approached 1.5, indicating mainly passive diffusion as the fluorine transport form at low concentration and active transport at high concentration. The three tea extracts also varied significantly in fluorine bioavailability, with a lower fluorine toxicity and bioavailability for post-fermented dark tea than green tea or black tea. The morphology of fluorine and the synergetic effect of polyphenol-oxidized polymers may be important influencing factors for fluorine bioavailability. This study has shed light on the absorption and transport of fluorine from different teas and facilitates the understanding of the related transport mechanism.