Vitamin C (ascorbic acid) has numerous biological functions. It is essential for the synthesis of collagen and glycosaminoglycans, which are the building materials of all connective tissues, such as skin, blood vessels, tendons, joint cartilage and bone. Vitamin C is the required coenzyme for two groups of enzymes that catalyze the crosslinking of collagen fibers – lysyl hydroxylases and prolyl hydroxylases. As such, vitamin C is essential for normal wound healing and capillary health. Vitamin C participates in the biosynthesis of carnitine, serotonin, and certain neurotransmitters, including norepinephrine. Vitamin C is among the most powerful antioxidants in humans and animals. It is a water-soluble, chain-breaking antioxidant that reacts directly with superoxide, hydroxyl radicals, and singlet oxygen. Laboratory studies show that vitamin C completely protects lipids in plasma and low-density lipoprotein (LDL) against peroxidative damage. In addition, vitamin C interacts with glutathione and alpha-lipoic acid, and regenerates vitamin E. The antioxidant functions of vitamin C appear to have clinical significance in providing protection from free radical damage to the eyes, lungs, blood and the immune system. Bioflavonoids (also called flavonoids) are a class of phytochemicals that are potent antioxidants, which scavenge many potentially damaging free radicals. Another aspect of the antioxidant properties of bioflavonoids is their synergy with vitamin C. The bitter tasting flavanones hesperidin and naringin, from the white albedo layer of citrus peels, have been shown to extend the nutritional functions of vitamin C. Bioflavonoids are also capable of binding to metal ions, which prevents these metals from acting as catalysts in the body to enhance free radical production. Many bioflavonoids, especially rutin and quercetin, support the health of the body’s circulatory system by helping maintain capillary blood flow and proper vascular permeability, integrity, and resiliency.