Citrus Bioflavonoid Complex. Gluten Free and Vegetarian. 500-C Methoxyflavone is a synergistic formula that features 500 mg of vitamin C per tablet and a specialized complex of full spectrum bioflavonoids including methoxyflavone such as hesperidin naringin neohesperidin narirutin eriocitrin didymin poncirin and other phenolic compounds. . Vitamin C is a powerful antioxidant that plays an important role in immune function and is essential for collagen production.