Natural chlorophyll inhibits aflatoxin B1-induced multi-organ carcinogenesis in the rat

Abstract

Chemoprevention by chlorophyll (Chl) was investigated in a rat multi-organ carcinogenesis model. Twenty-one male F344 rats in three gavage groups (N = 7 rats each) received five daily doses of 250 microg/kg [(3)H]-aflatoxin B(1) ([(3)H]-AFB(1)) alone, or with 250 mg/kg chlorophyllin (CHL), or an equimolar amount (300 mg/kg) of Chl. CHL and Chl reduced hepatic DNA adduction by 42% (P = 0.031) and 55% (P = 0.008), respectively, AFB(1)-albumin adducts by 65% (P < 0.001) and 71% (P < 0.001), respectively, and the major AFB-N(7)-guanine urinary adduct by 90% (P = 0.0047) and 92% (P = 0.0029), respectively. To explore mechanisms, fluorescence quenching experiments established formation of a non-covalent complex in vitro between AFB(1) and Chl (K(d) = 1.22 +/- 0.05 microM, stoichiometry = 1Chl:1AFB(1)) as well as CHL (K(d) = 3.05 +/- 0.04 microM; stoichiometry = 1CHL:1AFB(1)). The feces of CHL and Chl co-gavaged rats contained 137% (P = 0.0003) and 412% (P = 0.0048) more AFB(1) equivalents, respectively, than control feces, indicating CHL and Chl inhibited AFB(1) uptake. However, CHL or Chl treatment in vivo did not induce hepatic quinone reductase (NAD(P)H:quinone oxidoreductase) or glutathione S-transferase (GST) above control levels. These results are consistent with a mechanism involving complex-mediated reduction of carcinogen uptake, and do not support a role for phase II enzyme induction in vivo under these conditions. In a second study, 30 rats in three experimental groups were dosed as in study 1, but for 10 days. At 18 weeks, CHL and Chl had reduced the volume percent of liver occupied by GST placental form-positive foci by 74% (P < 0.001) and 77% (P < 0.001), respectively compared with control livers. CHL and Chl reduced the mean number of aberrant crypt foci per colon by 63% (P = 0.0026) and 75% (P = 0.0004), respectively. These results show Chl and CHL provide potent chemoprotection against early biochemical and late pathophysiological biomarkers of AFB(1) carcinogenesis in the rat liver and colon.

Heterocyclic Aromatic Amines Heterocomplexation with Biologically Active Aromatic Compounds and Its Possible Role in Chemoprevention

“…The protection resulted from decreased mutagen uptake from the intestines, which was concluded from the increased excretion of AFB1 in feces of CHL-and chlorophyll-fed animals. Moreover, molecular complexes formation between two anticarcinogens and AFB1 were confirmed by fluorescence quenching experiments, with 1 : 1 stoichiometries and dissociation constants = 1.22 M and 3.05 M for AFB1-chlorophyll and AFB1-CHL interactions, respectively [62]. CHL administered together with AFB1 in the diet inhibited AFB1-DNA binding in trout.…”

“…Direct interactions between chlorophyll, CHL and, dibenzo[a,l]pyrene (DBP) contributed to the reduced uptake of the mutagen to the liver, thus diminishing stomach and liver cancer incidents in rainbow trout [61]. Chemopreventive properties of natural chlorophyll and CHL were also described for another aromatic mutagen/carcinogen-AFB1, and AFB1-induced carcinogenesis in rats [62]. The protection resulted from decreased mutagen uptake from the intestines, which was concluded from the increased excretion of AFB1 in feces of CHL-and chlorophyll-fed animals.…”

The Antioxidant and Free Radical Scavenging Activities of Chlorophylls and Pheophytins

“…One proposed mechanism is that the chlorophyll porphyrin ring acts as an interceptor molecule, or desmutagen, by directly binding to other planar cyclic molecules through a shared pi-cloud [5][6][7]. Carcinogenic molecules with planar structures have been shown to be bound [7] and prevented from acting as carcinogens in biological systems [2,[7][8][9][10]. However, other carcinogenic molecules are not directly bound by chlorophyll compounds, yet are still less effective as mutagens in the presence of chlorophyll compounds [7].…”

Single-head broccoli response to nitrogen application

“…Leaves and stem are usually discarded. However, photosynthetic pigments production (chlorophyll and carotenoids) in the leaves, increased by N dose increase, indicates that this part should be exploited as food, mainly because chlorophyll and carotenoids are beneficial to human health (LANFER-MARQUEZ, 2003;SIMONICH et al, 2007;MCQUISTAN et al, 2012). In addition, broccoli leaves are a source of polyphenols, which are substances known for its antioxidant activity, as well as stems and leaves are rich in fiber and lipids (STORCK et al, 2013).…”

“…Increase in photosynthetic pigments content stimulates photosynthetic rate and the plant biomass production (ENGELS et al, 2012). Furthermore, higher chlorophyll content can promote a larger antioxidant, antimutagenic and chemopreventive activity in humans (LANFER-MARQUEZ, 2003), inducing cancer prevention (SIMONICH et al, 2007;MCQUISTAN et al, 2012) and contributing for healing process (TANAKA et al, 1997). Carotenoids are vitamin A precursors and also powerful antioxidants, working in the prevention of degenerative diseases (RODRIGUEZ-AMAYA, 2001;AMAN et al, 2005).…”