Abstract
Glucoraphanin is the main glucosinolate found in broccoli and other cruciferous vegetables (Brassicaceae). The objective of the study was to evaluate whether glucoraphanin and its breakdown product sulforaphane, are potent modulators of various phase I and phase II enzymes involved in carcinogen-metabolising enzyme systems in vitro. The glucosinolate glucoraphanin was isolated from cruciferous vegetables and exposed to human hepatoma cell line HepG2 at various concentrations (0-25 μM) for 24 hours. Glucoraphanin at higher concentration (25 μM) decreased dealkylation of methoxyresorufin, a marker for cytochrome P4501 activity; supplementation of the incubation medium with myrosinase (0.018 U), the enzyme that converts glucosinolate to its corresponding isothiocyanate, showed minimal induction in this enzyme activity at concentration 10 μM. Quinone reductase and glutathione S-transferase activities were unaffected by this glucosinolate; however, supplementation of the incubation medium with myrosinase elevated quinone reductase activity. It may be inferred that the breakdown product of glucoraphanin, in this case sulforaphane, is superior than its precursor in modulating carcinogen- metabolising enzyme systems in vitro and this is likely to impact on the chemopreventive activity linked to cruciferous vegetable consumption.
Highlights
Sulforaphane [1-isothiocyanato-4-(methylsulphinyl) butane] is a structurally-linked isothiocyanate possessing an aliphatic side chain which is present in large amounts in cruciferous vegetables and present as the glucosinolate, glucoraphanin
The objective of the study was to evaluate whether glucoraphanin and its breakdown product sulforaphane, are potent modulators of various phase I and phase II enzymes involved in carcinogen-metabolising enzyme systems in vitro
It may be inferred that the breakdown product of glucoraphanin, in this case sulforaphane, is superior than its precursor in modulating carcinogenmetabolising enzyme systems in vitro and this is likely to impact on the chemopreventive activity linked to cruciferous vegetable consumption
Summary
Sulforaphane [1-isothiocyanato-4-(methylsulphinyl) butane] is a structurally-linked isothiocyanate possessing an aliphatic side chain which is present in large amounts in cruciferous vegetables and present as the glucosinolate, glucoraphanin. Consumption of these vegetables has been repeatedly associated to lower cancer incidence in epidemiological studies, and it is believed that glucosinolates may be liable for this effect (Ambrosone et al, 2004; Lam et al, 2009). Sulforaphane induced cytotoxicity and lysosome- and mitochondria-dependent cell death in colon cancer cells with deleted p53, a tumour suppressor protein (Rudolf and Cervinka, 2011) Based on those findings, it was believed that the chemopreventive activity of cruciferous vegetables is completely the result of exposure to degradation products of glucosinolates, such as the aforementioned isothiocyanates, and that the parent glucosinolates make no contribution. Our finding is presented in the current paper that sulforaphane is a superior than its precursor
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