Vitamin C and Bio-Quercetin Phytosome is a high-potency vitamin C supplement enhanced with an ultra-absorbable form of quercetin. Vitamin C is a powerful antioxidant that also supports immune health, a healthy cardiovascular system, whole body health, and more. Quercetin is a flavonoid that complements vitamin C?s health benefits. Bio-quercetin is encased in a plant-derived phytosome delivery system, which makes it up to 50 times more bioavailable than a dose of standard quercetin. Vitamin C is a powerful antioxidant that provides profound whole-body health benefits. This supplement delivers 1,000 mg of vitamin C, along with 15 mg of an ultra-absorbable quercetin. Quercetin complements vitamin C?s activity in supporting whole-body health.