First‐Pass Metabolism of Chlorophylls in Mice

Abstract

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.

Influence of Alkaline Treatment on Structural Modifications of Chlorophyll Pigments in NaOH—Treated Table Olives Preserved without Fermentation

“…In plant foods, pheophytins, pheophorbides and pyroderivatives are the chlorophyll compounds that originate widely during thermal processing or fermentation of fruits, vegetables and green algae [ 47 ] while chlorophyll derivatives with phytyl-chlorin or phytyl-rhodin structures are specifically associated with the processing of alkali-treated table olives [ 26 , 27 , 31 ]. In another field, this type of derivatives has also been identified during the senescence of microalgaes incubated under oxic conditions [ 49 ], and more recently as secondary metabolites of digestion in mice from a diet rich in chlorophylls [ 50 ]. Its presence in the liver indicates the existence of alternative metabolic pathways that modify the structure of the chlorophyll macrocycle increasing its polarity and, as indicated by the authors [ 50 ], to facilitate probably a greater metabolism and/or excretion.…”

“…In another field, this type of derivatives has also been identified during the senescence of microalgaes incubated under oxic conditions [ 49 ], and more recently as secondary metabolites of digestion in mice from a diet rich in chlorophylls [ 50 ]. Its presence in the liver indicates the existence of alternative metabolic pathways that modify the structure of the chlorophyll macrocycle increasing its polarity and, as indicated by the authors [ 50 ], to facilitate probably a greater metabolism and/or excretion.…”

Carotenoids and Chlorophylls as Antioxidants

“…The major outcome is that chlorophylls a and b are transformed into their corresponding pheophorbides and pheophytins and are absorbed at similar rates as carotenoids. A further step has been to show that pheophorbide a is transported at the intestinal level by a protein-mediated mechanism, with scavenger receptor class B type 1 (SR-BI) being a plausible transporter [ 159 ]. These results have been confirmed at the in vivo level, using mice as the experimental model, showing a preferential accumulation of pheophorbide in the liver along with multiple other chlorophyll compounds [ 159 ].…”

“…A further step has been to show that pheophorbide a is transported at the intestinal level by a protein-mediated mechanism, with scavenger receptor class B type 1 (SR-BI) being a plausible transporter [ 159 ]. These results have been confirmed at the in vivo level, using mice as the experimental model, showing a preferential accumulation of pheophorbide in the liver along with multiple other chlorophyll compounds [ 159 ]. However, in humans, a trial was developed with copper chlorophylls, identifying copper chlorophyll e4 as the major component in serum [ 160 ].…”

Green Natural Colorants

“…At this point, and by means of comparative absorption experiments with the Caco-2 cellular model at different concentrations of pheophytins, it was hypothesized that the absorption process could correlate with a passive facilitated mechanism [42]. On the contrary, to decipher the kind of cellular transport process for pheophorbides, Viera et al [44] described the production of micelles rich in pheophorbide a to reach physiological micellar concentrations (7 μm). Pre-incubations of cell monolayers with different amounts of one specific inhibitor of the Scavenger Receptor class B type I (SR-BI) transporter (BLT1), significantly inhibited the uptake of pheophorbide a , which strongly suggests that SR-BI is involved in the transport of pheophorbide a .…”