In this article Dr. B states:

Unlike more complex antioxidants, which are
naturally made up of a mixture of antioxidants,
vitamin C or E alone can actually
produce free radicals. “They need to be
in the presence of a similar antioxidant
to counteract this effect,” says Baumann.
That’s why you often see vitamin C with
vitamin E, and sometimes also with ferulic
acid. “The combination of these three
more than doubles the sun protection in
the skin and prevents DNA mutations
from occurring,” says Sheldon R. Pinnell,
professor emeritus of dermatology at
Duke University School of Medicine.

www.skintypesolutions.com/media/Skin_Defenders.pdf

So does that mean you shouldn't use a product such as Potent-C 10.5 Concentrate by Biomedic (30 ml.) because it doesn't contain Vitamin E or ferulic acid?