Authors: Fahey, Jed W.¹; Stephenson, Katherine K.¹; Dinkova-Kostova, Albena T.¹; Egner, Patricia A.²; Kensler, Thomas W.²; Talalay, Paul¹

Source: Carcinogenesis, Volume 26, Number 7, 1 July 2005 , pp. 1247-1255(9)

Publisher: Oxford University Press

Abstract:

Plant chlorophylls and carotenoids are highly colored, conjugated polyenes that play central roles in photosynthesis. Other porphyrins (tetrapyrroles), such as cytochromes, which are structurally related to chlorophyll, participate in redox reactions in many living systems. An unexpected new property of tetrapyrroles, including tetramethyl coproporphyrin III, tetrabenzoporphine, copper chlorin e4 ethyl ester, and of carotenoids including zeaxanthin and -cryptoxanthin is their ability to induce mammalian phase 2 proteins that protect cells against oxidants and electrophiles. The capacity of these compounds to induce the phase 2 response depends upon their ability or that of their metabolites to react with thiol groups, a property shared with all other classes of phase 2 inducers, which show few other structural similarities. Pseudo second-order rate constants of these inducers are correlated with their potency in inducing the phase 2 enzyme NAD(P)H:quinone oxidoreductase 1 (NQO1) in murine hepatoma cells. One of the most potent inducers was isolated from chlorophyllin, a semisynthetic water-soluble chlorophyll derivative. Although chlorophyll itself is low in inducer potency, it may nevertheless account for some of the disease-protective effects attributed to diets rich in green vegetables because it occurs in much higher concentrations in those plants than the widely studied ‘phytochemicals’.

Document Type: Research article

DOI: http://dx.doi.org/10.1093/carcin/bgi068

Affiliations: 1: Lewis B. and Dorothy Cullman Cancer Chemoprotection Center, Department of Pharmacology and Molecular Sciences, School of Medicine, 2: Department of Environmental Health Sciences, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA

Publication date: 2005-07-01

More about this publication?

• Carcinogenesis is a multi-disciplinary journal that brings together all the varied aspects of research that will ultimately lead to the prevention of cancer in man. The journal will publish papers that warrant prompt publication in the areas of Cancer Biology, Molecular Epidemiology and Cancer Prevention, and Carcinogenesis.

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