polyphenols promote the regeneration of ascorbate (vitamin C), enhancing its antioxidant functions in the body. After ascorbate neutralizes a free radical, it becomes oxidized. Polyphenols can donate an electron to this oxidized ascorbate, restoring it to its active, reduced form.

The regeneration process

Ascorbate neutralizes free radicals: Ascorbic acid (the reduced form of vitamin C) functions as an antioxidant by donating an electron to neutralize reactive oxygen species (ROS).Ascorbate becomes oxidized: In the process of donating an electron, ascorbic acid becomes oxidized, turning into the ascorbyl radical.Polyphenols donate an electron: Polyphenols—a broad class of plant compounds—have antioxidant properties of their own. They can also donate an electron to the oxidized ascorbyl radical, reducing it and regenerating it back into active ascorbic acid.

When vitamin E is oxidized, it can be regenerated by ascorbic acid.
This creates a chain reaction where polyphenols regenerate vitamin C, which in turn regenerates vitamin E, bolstering the body's overall antioxidant defenses both inside and outside cell membranes.

While polyphenols are not inherently regenerative, some can be recycled indirectly. For example, vitamin C (a potent regenerative antioxidant) can assist in the regeneration of other antioxidants, including polyphenols and vitamin E.

Ascorbate Free Radical (AFR), also known as monodehydroascorbate

Enzymes called ascorbate free radical reductases (AFRases) can rapidly convert AFR back to ascorbic acid, helping to maintain cellular ascorbate levels and continue the antioxidant cycle.

Compounds that regenerate Vitamin C (ascorbic acid) include dehydroascorbic acid (DHA), the oxidized form of ascorbic acid, which can be readily reduced back to ascorbic acid in a reversible process. Other compounds that participate in or facilitate this regeneration include glutathione (GSH) and NADPH, which serve as electron donors in enzymatic processes, as well as other antioxidants like α-tocopherol (vitamin E) and certain flavonoids.

Vitamin C is necessary for the hydroxylation of amino acids, which are critical for stabilizing collagen's structure. Without enough Vitamin C, the body may not be able to effectively utilize the sulfur provided by MSM for collagen formation.

Pro-Oxidant Effect: Unlike its well-known antioxidant role at lower concentrations, at these high levels, vitamin C acts as a "prodrug" to generate significant amounts of hydrogen peroxide.

Tumor Cell Susceptibility: Tumor cells are often less effective at clearing hydrogen peroxide due to lower levels of the enzyme catalase, which normally breaks it down. This difference in catalase activity can lead to selective damage and death of cancer cells exposed to high-dose vitamin C.

Increased production under high light: A plant's vitamin C content increases under high light intensity to combat the additional oxidative stress. Research shows that genetically modifying crops to improve vitamin C transport could increase their tolerance to strong light.

Primary site for vitamin C activity: Leaves, particularly the chloroplasts of photosynthetic cells, contain the highest concentration of vitamin C in plants. Here, vitamin C protects the photosynthetic machinery from light-induced damage.

Light-dependent regulation: High light intensity during the growing season generally leads to higher vitamin C content in leaf tissue.