American Health Ester-C Powder with Citrus Bioflavonoids 750 mg. - 8 oz. American Health Ester-C Powder with Citrus Bioflavonoids is a breakthrough patented formula that contains naturally-occurring Vitamin C metabolites. American Health non-acidic Ester C is quickly absorbed. American Health s Ester-C s unique manufacturing process neutralizes pH making it gentle on the digestive system.