Solgar Quercetin Complex with Ester-C Plus is a unique formula for natural seasonal support. Quercetin is a bioflavonoid found naturally in onions and other foods. It has antioxidant properties which help stabilize cell membranes. Ester-C Plus is a patented, pH neutral form of vitamin C that is gentle on the stomach. Ester-C Plus offers the additional benefits of incorporating acerola berry, citrus bioflavonoids, rutin and rose hips. Solgar's formula also features bromelain, a natural enzyme derived from pineapple. Free of gluten, wheat, dairy, soy, yeast, sugar, sodium, artificial flavor, sweetener, preservatives and color.