Do bioflavonoids enhance Vitamin C absorption?

Vitamin C absorption from the gut is governed by sodium content for active transport. For passive absorption throughout the length of the intestine the vitamin does not use a similar co-factor.

The bioflavonoids come into play after vitamin C has been absorbed and is in circulation.  This vitamin has a relatively short half-life and depends on other antioxidants to act as electron donors to 'reduce' oxidized vitamin C (dehydroascorbate) back into the antioxidant form (ascorbate; ascorbic acid).  Various antioxidants, including bioflavonoids and polyphenols in fruits, are typically used to provide that extra benefit.  So the recycling and longevity of vitamin C after absorption depends greatly on the presence of other antioxidants; including not only rutin and bioflavonoids but also alpha lipoic acid, glutathione, and numerous other antioxidants.

So there is a benefit to using a base, often called vitamin C complex, in a vitamin C formula, but not so much in the initial absorption as in the vitamin's retention and recycling for re-use over time.  The variety of antioxidant-related nutrients in the human diet is thought responsible for why humans can retain vitamin C between meals when we cannot manufacture our own from blood sugar at will, as most mammals can.