Bioflavonoid rescue of ascorbate at a membrane interface

Area of Science:

• Biochemistry
• Cell Biology
• Oxidative Stress

Background:

• Cytochrome c is a vital protein in cellular respiration and apoptosis.
• Oxidative damage from reactive oxygen species (ROS) can impair cytochrome c function.
• Ascorbate (Vitamin C) is a known antioxidant, but its efficacy in membrane environments is debated.

Purpose of the Study:

• To investigate the protective effects of ascorbate on cytochrome c in the presence of lipid membranes.
• To determine the role of bioflavonoids in enhancing ascorbate's antioxidant activity in a hydrophobic environment.
• To elucidate the mechanism of bioflavonoid-mediated electron transfer from ascorbate.

Main Methods:

• Experiments were conducted in aqueous solutions and liposomes mimicking mitochondrial membranes.
• Protection of cytochrome c from bleaching by hydrogen peroxide and t-butyl hydroperoxide was measured.
• The effects of ascorbate, bioflavonoids (epicatechin, quercetin, rutin), and Trolox were assessed, alone and in combination.

Main Results:

• Ascorbate effectively protected cytochrome c in aqueous solution but failed in liposomes.
• Bioflavonoids epicatechin and quercetin, similar to TMPD, restored ascorbate's protective function in liposomes.
• Quercetin synergistically enhanced ascorbate's protection, while rutin and Trolox were less effective.

Conclusions:

• Bioflavonoids are crucial for mediating ascorbate's electron transfer into hydrophobic membrane environments.
• Certain bioflavonoids are essential for the antioxidant protection of cytochrome c within biological membranes.
• This highlights a potential role for bioflavonoids in modulating cytochrome c's hydroperoxidase activity and overall cellular redox balance.