Ester c174 calcium ascorbate is a unique and patented non acidic form of vitamin c ester c174 functions biologically like other forms of vitamin c but has the added benefit of quicker absorption and longer retention in the immune system healthaid ester c174 plus formulation contains natural flavonoids rutin quercetin citrus bioflavonoids hesperidin acerola and rosehip making this a unique complex powerful antioxidant to help boost the immune system and prevent colds and f