Protective effects of broccoli extracts and sulforaphane against hydrogen peroxide induced oxidative stress in B16 cells

The antioxidant activity of broccoli extracts and its purified compounds (polyphenols and purified sulforaphane (PSF)) was investigated. Broccoli extracts and SF protected B16 cells from H2O2-induced oxidative stress through increasing total antioxidant capacity (T-AOC) and activities of NADPH dehydrogenase quinone1 (NQO1) and catalase (CAT), and decreasing content of malondialdehyde (MDA). Western blot and qRT-PCR revealed that the expression of nuclear factor erythroid 2-related factor 2 (Nrf2), NQO1 and heme oxygenase 1 (HMOX-1) was increased. Broccoli extracts was better than SF in improving T-AOC, antioxidant enzyme activity (especially, NQO1) and reducing MDA content. Polyphenols and PSF were separated from broccoli extracts by high-speed countercurrent chromatography (HSCCC). They could significantly increase T-AOC and NQO1 activities (P < 0.05). PSF increased activities of Phase 2 enzymes more than polyphenols. Broccoli extracts protected B16 cells from H2O2-induced oxidative stress via enhancing Nrf2/Keap1 signaling pathway. The protection was mainly attributable to SF, followed by polyphenols.