Vitamin C, 100% L-Ascorbic Acid, USP, Ultrafine powder is a water soluble antioxidant.Vitamin C, a potent, naturally occurring antioxidant is an important constituent of skin. It plays a pivotal role in the prevention of dry skin and wrinkles, collagen synthesis and skin regeneration.itamin C, 100% L-Ascorbic Acid, USP, Ultrafine powder is a water soluble antioxidant.