Solgar's Quercetin Complex includes the important flavonoid quercetin in a synergistic formula with Ester-C Plus and Brome-lain. Ester-C Plus is exclusively formulated by Solgar and provides a patented method of supplementing pH neutral (non-acidic) vitamin C to prevent stomach irritation. In addition, Ester-C Plus includes the vitamin C metabolites, L-threonic acid, L-lyxonic acid and L-xylonic acid, that occur along with vitamin C in nature. A special manufacturing process is employed to form a unique calcium ascorbate metabolite complex. Solgar's Ester-C Plus offers the additional benefits of acerola, citrus bioflavonoids, rutin and rose hips in the Ester-C ascorbate metabolite complex