Sulforaphane is Superior to Glucoraphanin in Modulating Carcinogen-Metabolising Enzymes in Hep G2 Cells

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, arepotent modulators of various phase I and phase II enzymes involved in carcinogen-metabolising enzyme systems invitro. The glucosinolate glucoraphanin was isolated from cruciferous vegetables and exposed to human hepatomacell line HepG2 at various concentrations (0-25 μM) for 24 hours. Glucoraphanin at higher concentration (25μM) decreased dealkylation of methoxyresorufin, a marker for cytochrome P4501 activity; supplementation ofthe incubation medium with myrosinase (0.018 U), the enzyme that converts glucosinolate to its correspondingisothiocyanate, showed minimal induction in this enzyme activity at concentration 10 μM. Quinone reductaseand glutathione S-transferase activities were unaffected by this glucosinolate; however, supplementation of theincubation medium with myrosinase elevated quinone reductase activity. It may be inferred that the breakdownproduct of glucoraphanin, in this case sulforaphane, is superior than its precursor in modulating carcinogenmetabolisingenzyme systems in vitro and this is likely to impact on the chemopreventive activity linked tocruciferous vegetable consumption.