Digestive stability, human intestinal cell uptake, and bioactivity of dietary chlorophyll derivatives

Increased fruit and vegetable consumption has been associated with a decreased risk of specific chronic diseases. Consequently, interest in plant food phytochemicals as potential physiologically active agents has intensified. A relationship between antimutagenic activity and chlorophyll content for a number of common vegetable extracts has been made and specific natural and commercial grade derivatives have been identified as possible bioactive agents with powerful antimutagenic and antioxidative activities. While these results have been promising, very little is known regarding human digestion, absorption, and metabolism of dietary chlorophyll derivatives. Susceptibility of these pigments to heat and acid may modulate observed chemopreventive activity of native compounds as they are modified through the gastrointestinal tract.; The present study was designed to qualitatively and quantitatively investigate digestive modifications occurring to dietary chlorophylls, and to assess the potential roles these derivatives have in human health with regard to their availability, as well as antioxidant and antimutagenic activity. Both natural and commercial grade chlorophylls were subjected to two stage in vitro digestion followed by introduction to a Caco-2 human intestinal cell culture model. Native chlorophylls quantitatively degraded to metal free pheophytins during the in vitro process whereas metallo-chlorophylls such as Zn-pheophytins and Cu-chlorins were stable during simulated digestion. Both water soluble and lipophilic chlorophyll pigments were accumulated intact by monolayers of Caco-2 human intestinal cells, suggesting that these compounds may be absorbed by humans.; Predominant dietary chlorophyll derivatives demonstrated potential antioxidant activity through their ability to scavenge long-lived free radicals such as 1,1-diphenyl-2-picrylhydrazyl (DPPH·) and 2,2 ′-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS ·+). Metal-free pheophytin and pyropheophytin derivatives were found to have limited antioxidant activity compared to magnesium, zinc and copper chelates, illustrating that digestive and food processing induced alterations may affect the antioxidative potential of natural chlorophyll derivatives. However, both metal-free and metallo-chlorophyll derivatives exhibited dose-dependent inhibitory activity against benzo[a]pyrene induced mutagenesis in Salmonella typhimurium TA100, demonstrating that strong antimutagenic activity is most likely retained during processing and digestive modification of the natural chlorophyll structure. Information gained from these studies has provided basic information critical to the understanding of the digestion, uptake, metabolism, and potential bioactivity of chlorophylls in humans. This information will facilitate the design of future investigations evaluating the association between consumption of chlorophylls and modulation of disease outcomes.