A major inducer of anticarcinogenic protective enzymes from broccoli: isolation and elucidation of structure.
Level 5 - mechanism / opinion, no new human data
Preclinical in vitro cell culture and rodent tissue study
PubMed 1549603 · doi:10.1073/pnas.89.6.2399
What was done
Using quinone reductase induction in cultured murine hepatoma cells as a bioassay, the authors isolated and identified the major Phase II detoxication enzyme inducer from SAGA broccoli (*Brassica oleracea italica*). They chemically synthesized racemic sulforaphane and structural analogues varying in sulfur oxidation state (sulfide, sulfoxide, sulfone) and carbon chain length to examine structure-activity relationships, and evaluated enzyme induction (quinone reductase and glutathione S-transferase) in murine hepatoma cells and mouse tissues.
What was found
The active compound was identified as (-)-1-isothiocyanato-(4R)-(methylsulfinyl)butane (sulforaphane). It was shown to be a monofunctional inducer that selectively upregulated Phase II enzymes without inducing aryl hydrocarbon receptor-dependent cytochrome P-450 (Phase I) enzymes. Sulforaphane was the most potent analogue tested, with the presence of oxygen on the sulfur enhancing inducer potency. Sulforaphane and its sulfide and sulfone analogues induced quinone reductase and glutathione S-transferase in mouse tissues. The abstract reports no numerical values, concentrations, or effect sizes.
Why it matters
This study provided the first identification of sulforaphane as the primary bioactive Phase II enzyme inducer in broccoli, offering a specific chemical mechanism to explain how cruciferous vegetables exert chemoprotective effects against carcinogens.
Limits
The study is entirely preclinical, relying on murine hepatoma cell lines and mouse tissue assays without human pharmacokinetic, efficacy, or safety data. The abstract does not provide sample sizes, dosages, or quantitative measurements of enzyme activity.
Cited by
- supports Sulforaphane was identified in broccoli by Paul Talalay and Yanyan Zhang in 1992 as an inducer of Phase 2 cytoprotective enzymes in cell culture and animal models.