Assessment of degradation and intestinal cell uptake of carotenoids and chlorophyll derivatives from spinach puree using an in vitro digestion and caco-2 human cell model

Although numerous studies have demonstrated the health benefits of chloroph yll derivatives, information regarding the digestion, absorption, and metab olism of these phytochemicals is quite limited. To better understand the di gestion of these pigments, green vegetables including fresh spinach puree ( FSP), heat- and acid-treated spinach puree (HASP), and ZnCl2-treated spinac h puree (ZnSP) were subjected to an in vitro digestion method which simulat es both the gastric and small intestinal phases of the process. Native chlo rophylls were converted to Mg-fi-ee pheophytin derivative's during digestio n. Conversely, Zn-pheophytins were completely stable during the digestive p rocess. Transfer of lipophilic chlorophyll derivatives, as well as the caro tenoids lutein and beta -carotene, into the aqueous micellar fi action from the food matrix was quantified. Micellarization of total chlorophyll deriv atives differed significantly (p < 0.05) for FSP (37.6%), HASP (17.2%), and ZnSP (8.7%). Micellarization of chlorophyll a derivatives was determined t o be significantly more efficient than chlorophyll b derivatives in FSP and HASP (p < 0.01), but not in ZnSP (p > 0.05). Intestinal cell uptake of mic ellarized pigments was investigated using HTB-37 (parent) and clonal TC7 li nes of human Caco-2 cells. Medium containing the pigment-enriched fraction generated during digestion was added to the apical surface of fully differe ntiated monolayers for 4 h. Pigments were then extracted from cells and ana lyzed by C18 HPLC with photodiode array detection. Both Caco-2 HTB-37 and T C7 clone cells accumulated 20-40% and 5-10% of micellarized carotenoid and chlorophyll derivatives, respectively. These results are the first to demon strate uptake of chlorophyll derivatives by human intestinal cells and to s upport the potential importance of chlorophylls as health-promoting phytoch emicals.