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PubMed1988

Photodynamic toxicity of porphyrins and chlorins for a human tumor cell line: combined light and concentration dose responses for the retained fraction.

In recent years porphyrins and related materials have been tested as antitumor agents. A technique was devised to obtain dose-response curves for the sensitizer fraction that resists one day of elution by tissue culture medium--the retained fraction. We found a steep "threshold" dose response relationship that helps to explain tumor destruction without damage to normal tissues. The family of dose-response curves produced by a wide range of light exposures suggests that chlorins and porphyrins do not act by identical mechanisms. Moreover, they suggest that chlorins will prove superior in practical use.

Carcinoma↗
PubMed1992

Sn-chlorin e6 antibacterial immunoconjugates. An in vitro and in vivo analysis.

Monoclonal antibody-Sn-chlorin e6 immunoconjugates were prepared by the site-selective covalent modification of the monoclonal oligosaccharide moiety. By carefully controlling the reaction conditions and introducing triethanolamine groups as axial ligands of the Sn moiety, conjugates with in vivo biodistribution properties similar to underivatized IgG were prepared. By varying the reaction conditions, conjugates were reproducibly prepared with a range of photosensitizer to mAb molar ratios from 1.6 to 10. Based on a competitive inhibition radioimmunoassay, conjugates prepared by this method showed selectivity and binding affinity comparable to the unmodified antibody. The immunoconjugates had only slightly lower singlet oxygen yields than that observed with the Sn-chlorin e6 precursor indicating that negligible aggregation or structural modification of the chromophores occurred during the synthesis process. In vitro cell killing experiments demonstrated that all conjugates possessed significant cytotoxic activity. Biodistribution studies in mice showed that conjugates prepared with axial ligands had significant serum retention 24 h after injection while conjugates prepared without the triethanolamine ligand were much more rapidly cleared. In vivo specificity was demonstrated using rats infected with Fisher immunotype I P. aeruginosa at a site in the left posterior thigh muscle. Target to background ratios exceeded 60 at 120 h after conjugate injection of the specific immunoconjugate, compared to a ratio of only 6 for a non-specific mouse IgG conjugate. Biodistribution patterns at 120 h post injection indicate that the conjugates were both biologically active and structurally intact.

Animals↗
PubMed1985

Antimutagenic activity of some naturally occurring compounds towards cigarette-smoke condensate and benzo[a]pyrene in the Salmonella/microsome assay.

Several compounds, occurring in food, were tested for antimutagenic activity towards cigarette-smoke condensate (CSC) and benzo[a]pyrene (BaP). Antimutagenicity was determined in the Salmonella/microsome test, with tester strain TA98, in the presence of rat-liver homogenate. Dose-response curves did show reduction of CSC- and BaP-induced mutagenicity by ellagic acid, riboflavin and chlorophyllin. Chlorophyll a and chlorophyll b, although less distinct, also inhibited CSC- and BaP-induced mutagenicity. Ascorbic acid, beta-carotene, tocopherol acetate, chlorogenic acid and butyl hydroxyanisole did not have any influence on the mutagenicity of CSC and BaP. The similarity in results for cigarette-smoke condensate and for BaP indicates that a general mechanism may be involved in the inhibition of CSC- and BaP-induced mutagenicity.

Animals↗
PubMedDate not supplied

The metabolic activation of 4-nitro-o-phenylenediamine by chlorophyll-containing plant extracts: the relationship between mutagenicity and antimutagenicity.

Chlorophyllin, the sodium and copper salt of chlorophyll, chlorophyll a, and chlorophyll b were tested for their ability to inhibit the mutagenic activity of the direct-acting mutagen 4-nitro-o-phenylenediamine (NOP) and its plant-activated mutagenic enhancement. All three forms of chlorophyll were antimutagenic against both NOP and its plant-activated product, with chlorophyllin proving most effective. Chlorophyll-containing plant extracts, however, proved very efficient at activating NOP into a mutagen of greater potency. When these extracts were assayed for total chlorophyll content it was found that they contained far less chlorophyll than was required for an antimutagenic effect to occur. Thus, the balance between chemical mutagen activation and/or enhancement by chlorophyll-containing plant extracts and the potential antimutagenicity of these plant extracts is a function of chlorophyll concentration. The data presented here indicate that this balance must be taken into consideration in future studies investigating the efficacy of complex natural plant extracts as antimutagenic substances.

Biotransformation↗
PubMed1993

Binding of polycyclic planar mutagens to chlorophyllin resulting in inhibition of the mutagenic activity.

Chlorophyllin is known to inhibit the mutagenicity of a variety of compounds. Using highly purified samples of chlorophyllin and its family compounds, we studied the mechanism of the inhibition. Since mutagens with polycyclic planar structures are particularly strongly inhibited, it seemed likely that the inhibition arises by trapping of the mutagens by chlorophyllin through complex formation at the planar surfaces of these molecules. To explore this possibility, we prepared a Sepharose bearing covalently linked chlorophyllin as ligand, and the adsorption of mutagens to this Sepharose was measured. Three different chlorophyllin derivatives were used, i.e., copper-chlorin, iron-chlorin and chlorin, to investigate the role of metal in the center of the chlorophyllin chromophore. Adsorption of 37 different compounds, mostly mutagens, in 0.02 M Tris-HCl buffer at pH 8.0 to these chlorophyllin-Sepharose preparations was studied in a quantitative manner. The results showed that most of the compounds having three or more fused rings were strongly adsorbed with apparent dissociation constants of 10(-5)-10(-6) M, whereas those having two fused rings or one ring were only poorly adsorbed. Since the three Sepharose adsorbents gave similar adsorption profiles, it appeared that the central metal in the chlorophyllin molecule does not play a crucial role in the adsorption. We also measured the inhibitory effect of copper-chlorin against the mutagenicity of some of these compounds using the Salmonella assay. The results showed that those mutagens that were strongly adsorbable to copper-chlorin-Sepharose were subject to efficient inhibition by copper-chlorin, whereas many of those only poorly adsorbed were inhibited only weakly. We concluded that trapping by complex formation plays a role in the antimutagenic actions of chlorophyllin against many mutagens, particularly notable being the actions against ICR-170, quinacrine, aflatoxin B1, Trp-P-1 and Trp-P-2. An unusual behavior of Trp-P-2 in the adsorption process, i.e., a very tight complex formation at an extremely low Trp-P-2 concentration, was found; the implication of this phenomenon in relation to the real environmental setting is discussed.

Adsorption↗
PubMed1994

Mechanisms of the in vitro antimutagenic action of chlorophyllin against benzo[a]pyrene: studies of enzyme inhibition, molecular complex formation and degradation of the ultimate carcinogen.

Mechanisms of the antimutagenic action of chlorophyllin (CHL) towards benzo[a]pyrene (BP) were studied in vitro. In the Salmonella assay, CHL inhibited the mutagenic activity of BP in the presence of an S9 activation system and was particularly effective against the direct-acting ultimate carcinogen, benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE). Spectral studies indicated that the time-dependent hydrolysis of BPDE to tetrols was augmented in the presence of CHL concentrations on the order of 5 microM. Dose-related inhibition of several cytochrome P450-dependent enzyme activities was observed upon addition of CHL to in vitro incubations. Spectral changes for the interaction between CHL and cytochrome P450 indicated that CHL does not bind to the active site of the enzyme, but exerts its inhibitory effect indirectly. This was achieved by inhibiting NADPH-cytochrome P450 reductase (Ki approximately 120 microM with cytochrome c as substrate), and did not involve lowering of the effective substrate concentration by complex formation with the procarcinogen. It is concluded that the in vitro antimutagenic activity of CHL towards BP involves accelerated degradation of the ultimate carcinogen, with inhibition of carcinogen activation occurring only at high CHL concentrations. The latter mechanism is unlikely to occur in vivo following p.o. administration due to the limited uptake of CHL from the gut, but tissue concentrations may be sufficiently high to cause degradation of BPDE.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1996

Activity profiles of antimutagens: in vitro and in vivo data.

In this review, retinol, chlorophyllin, and N-acetylcysteine are examined and compared with regard to their antimutagenic activity against some promutagens and a group of direct-acting alkylating agents. The promutagens included aflatoxin B1, certain polycyclic aromatic hydrocarbons (e.g., benzo[a]pyrene), and certain heterocyclic amines (e.g., food pyrolysates). Results of antimutagenicity testing selected from data surveyed in the published literature are displayed graphically as activity profiles of antimutagens showing both the doses tested and the extent of inhibition or enhancement of mutagenic activity. All three antimutagens are discussed in terms of their putative mechanisms of action in vitro and in vivo with emphasis on the xenobiotic metabolizing enzyme systems.

Acetylcysteine↗
PubMed1996

Utility of a test for chromosomal malsegregation in Saccharomyces cerevisiae strain D61.M for the detection of antianeugens: test of the model combination of chlorophyllin and nocodazole.

Despite the fact that aneuploidy is a major genetic cause of human morbidity and mortality, antimutagenicity studies have used predominantly short-term tests that detect gene mutations, chromosomal aberrations, and micronuclei. Therefore, the major deficiency in the use of short-term tests for antimutagenicity studies is those that detect chromosomal malsegregation leading to aneuploidy. Thus, we initiated a study on the utility of short-term tests for the detection of antianeugenic activity. We selected strain D61.M of Saccharomyces cerevisiae, nocodazole, and chlorophyllin as a model short-term test, aneugen, and antimutagen, respectively, for our initial study. Chlorophyllin strongly inhibited the aneugenic activity of nocodazole, but had no effect on the endpoints when tested alone, in strain D61.M. To our knowledge, this is the first report of an antianeugen. Furthermore, we conclude that strain D61.M can be used as a relatively simple, inexpensive, and rapid short-term test for the study of antianeugenicity.

Aneuploidy↗
PubMed1994

Chlorophyll and chlorophyllin as modifiers of genotoxic effects.

Reports on an inverse relationship between the consumption of fresh vegetables and human gastrointestinal cancer have been followed by screening for the protective activity of a large number of plant extracts, including leafy vegetables. Chlorophyll is ubiquitous in all green plant parts. Chlorophyllins are derivatives of chlorophyll in which the central magnesium atom is replaced by other metals, such as cobalt, copper or iron. An attempt has been made in this article to review the relative efficacy of chlorophyll and chlorophyllin in modifying the genotoxic effects of various known toxicants.

Animals↗
PubMed1989

Comparative antimutagenicity of 5 compounds against 5 mutagenic complex mixtures in Salmonella typhimurium strain TA98.

Using the Ames Salmonella/microsome assay, we compared the antimutagenic activities of chlorophyllin, retinol, beta-carotene, vitamin C, and vitamin E against solvent extracts of coal dust, diesel emission particles, airborne particles, fried beef, and tobacco snuff. The results show that chlorophyllin inhibited 69% of the mutagenic activity of tobacco snuff and over 90% of that of the other 4 complex mixtures. Retinol inhibited 29-48% of the mutagenic activity of all 5 complex mixtures. beta-Carotene, vitamin C, and vitamin E inhibited, if any, less than 39% of the activity of the complex mixtures studied. Vitamin C enhanced the mutagenicity of airborne particles. These results indicate that for these dietary and environmental complex mixtures chlorophyllin is a more effective antimutagen than retinol, beta-carotene, vitamin C, and vitamin E.

Air↗
PubMed1994

Role of chlorophyllin as an in vivo anticlastogen: protection against gamma-radiation and chemical clastogens.

Chlorophyllin was evaluated in the mouse bone marrow micronucleus test for its possible protective effects against chromosomal damage induced by gamma-radiation, cyclophosphamide, N-nitroso-N-ethylurea and urethane. Three doses of chlorophyllin (50, 100 and 200 mg/kg, b.w.) were orally administered to mice 2 h before exposure to the clastogens under investigation. The results obtained demonstrated that chlorophyllin can significantly reduce the incidence of micronucleated polychromatic erythrocytes induced by gamma-radiation (1.15 Gy) and all the three chemical clastogens. However with the exception of cyclophosphamide there was no indication of a dose response for the in vivo anticlastogenic effects of chlorophyllin.

Animals↗
PubMed1994

In vivo effect of chlorophyllin on gamma-ray-induced sister chromatid exchange in murine bone marrow cells.

The aim of the present work is to determine the radioprotective capacity of chlorophyllin, by measuring the reduction of gamma-ray-induced sister-chromatid exchange (SCE) in murine bone marrow cells in vivo. The results obtained in two separate experiments, using 10, 50 and 100 micrograms of chlorophyllin per g of body weight (bw), indicate that chlorophyllin per se did not have any effect on the SCE frequency and that the dose of 100 micrograms/g bw protects 100% against the induction of SCE by 1.0 Gy of gamma-rays; 50 micrograms/g bw protects less than 50% and 10 micrograms/g bw affords no protection.

Animals↗
PubMed1996

Effect of chlorophyllin on gamma ray induced micronuclei in polychromatic erythrocytes of murine peripheral blood determined by the ABC strategy.

The effect of chlorophyllin on micronucleated polychromatic erythrocyte (MN-PCE) induction by gamma ray exposure in peripheral blood of mice was studied. The area beneath the curve (ABC) of MN-PCE frequency versus time was used as an index of total MN-PCE induction. The dose of 200 mg chlorophYllin per kg of body weight caused a slight, but not significant, reduction of the MN-PCE caused by 1.0 Gy exposure. This result indicates that chlorophyllin did not protect the cells against MN induction. In previous studies it was observed that the same chlorophyllin dose was able to protect 100% against sister chromatid exchange (SCE) induction by 1.0 gamma rays in both murine spermatogonia and bone marrow cells. These contradictory results indicate that chlorophyllin did not protect cells by scavenging free radicals, but by other mechanism, i.e. stimulating repair of lesions involved in SCE induction.

Animals↗
PubMed1995

In vivo radioprotective effect of chlorophyllin on sister chromatid exchange induction in murine spermatogonial cells.

The radioprotective capacity of chlorophyllin was determined by measuring the reduction of gamma-ray-induced sister chromatid exchange (SCE) in murine spermatogonia in vivo. The results obtained in experiments using 100 and 200 micrograms of chlorophyllin per gram of body weight (bw) and irradiated either before or after BrdU incorporation, indicate that a chlorophyllin dose of 200 micrograms/g bw protects 100% against the induction of SCE by 0.75 Gy of gamma-rays and 100 micrograms/g bw protects less than 50%. Chlorophyllin per se did not have any effect on the SCE frequency.

Animals↗
PubMed1995

Inhibitory effect of hemin, chlorophyllin and related pyrrole pigments on the mutagenicity of benzo[a]pyrene and its metabolites.

Hemin and chlorophyllin are known to inhibit strongly the mutagenicity of benzo[a]pyrene in the Salmonella assay. To further investigate this phenomenon, a series of these pyrrole pigments including pure samples of Cu- and Fe-chlorins were tested for their potency to inhibit the mutagenicity of benzo[a]pyrene and its metabolites, benzo[a]pyrene-7,8-diol, benzo[a]pyrene-4,5-epoxide, and benzo[a]pyrene-7,8-diol-9,10-epoxide. Hemin was the most potent among the pigments tested for these inhibitions. Both hemin and Cu-chlorin accelerated efficiently the degradation of benzo[a]pyrene-7,8-diol-9,10-epoxide, and this acceleration seemed to be the predominant mechanism by which these pigments inhibit the overall mutagenicity of benzo[a]pyrene in Salmonella. Based on spectroscopic evidence, we speculate that a complex formation between hemin and benzo[a]pyrene-7,8-diol-9,10-epoxide takes place and that this complexing is the cause of the accelerated degradation.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1986

Chlorophyllin: a potent antimutagen against environmental and dietary complex mixtures.

Chlorophyllin, the sodium and copper salt of chlorophyll, was tested for its ability to inhibit the mutagenic activity of a variety of complex mixtures--extracts of fried beef, fried shredded pork, red grape juice, red wine, cigarette smoke, tobacco snuff, chewing tobacco, airborne particles, coal dust and diesel emission particles--in strain TA98 of Salmonella typhimurium. Chlorophyllin was highly effective against the mutagenicity (90-100% inhibition) of 8 of these 10 mixtures. The mutagenicity of the other 2 mixtures was inhibited 75-80% at the highest concentration of chlorophyllin studied. Control and reconstruction experiments showed that chlorophyllin was not toxic to Salmonella at the concentrations used. The antimutagenic activity of chlorophyllin was heat-stable. The mechanism of the antimutagenicity of chlorophyllin in these experiments is not known; however, chlorophyllin is an antioxidant. Scavenging of radicals and/or interaction with the active group of mutagenic compounds may be responsible for its antimutagenic activity. The data reported here indicate that chlorophyllin is potentially useful as an antimutagenic agent.

Chlorophyll↗