Since 1947 With Ester-C Plus Unique Synergistic Formula Immune Health Support Gluten, Wheat & Dairy Free Suitable for Vegans Certified Gluten Free Kosher Parve Dietary Supplement Solgar Quercetin Complex includes the important bioflavonoid Quercetin in a synergistic formula with Ester-C Plus to provide unique antioxidants as well as immune health support. Quercetin is found in onions and other foods. It possesses antioxidant properties which help to stabilize cell membranes. Ester-C Plus provides a patented, pH neutral (non acidic), 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. This formula also features bromelain, a natural enzyme derived from pineapple.