Ester-C with Bioflavonoids contains a non-acidic form of vitamin C, which allows the vitamin-C to be absorbed faster than excreted; supplies vitamin C at the circulatory and tissue level; allows large doses to be taken without side effects; and is enriched with bioflavonoids which provide antiviral, anti-cancer, antihistamine, and antioxidant properties, and enhance absorption of the vitamin C. Dietary Supplement. Ester-C is a unique form of Vitamin C containing naturally occurring metabolites. Ester-C's patented manufacturing process neutralized the pH, making Ester-C gentle on the digestive system. Ester-C brand of Vitamin C is a unique form of Vitamin C containing naturally occurring Metabolites. Ester-C's patented manufacturing process neutralizes the pH, making Ester-C gentler and easier on the digestive system, unlike other Vitamin C products that are often more acidic.