First-Pass Metabolism of Chlorophylls in Mice

Abstract

Scope: The dietary intake of chlorophylls is estimated to be ≈50 mg d^-1 . However, their first pass metabolism and systemic assimilation is not well characterized.

Methods and results: A group of 30 mice are fed a diet rich in chlorophylls, while 10 mice received a standard diet without chlorophylls (control group). Liver extracts are analyzed every 15 days by HPLC-ESI(+)/APCI(+)-hrTOF- MS/MS to measure the accretion of specific chlorophyll metabolites. The chlorophyll profile found in the livers of mice fed a chlorophyll-rich diet shows that the formation and/or absorption of pheophorbides, pyro-derivatives, and phytyl-chlorin e₆ require the occurrence of a precise first-pass metabolism. In addition, the apical absorption of pheorphorbide a-rich micelles is significantly inhibited in Caucasian colon adenocarcinoma-2 cells pre-incubated with BLT1.

Conclusion: Pheophorbide a absorption is, at least partly, protein-mediated through SR-BI. This active absorption process could explain the specific accumulation of pheophorbide a in the livers of animals fed a chlorophyll-rich diet. A complementary mechanism could be the de-esterification of pheophytin a in the liver, yielding pheophorbide a and phytol, which can explain the origin of phytol in the liver. Hence, the results suggest two molecular mechanisms responsible for the accumulation of the health-promoting compounds pheophorbide and phytol.

Keywords: SR-BI; absorption; chlorophylls; liver; pheophorbide.