Solaray QBC Plex™ is an effective blend of quercetin, bromelain and Vitamin C. Quercetin may help support normal healthy sinus, respiratory and immune function. Bromelain is a plant enzyme known to help breakdown protein. Vitamin C provides antioxidant activity and is intended to help normal, healthy collagen synthesis, capillary and blood vessel integrity, cartilage and bone development, immune function and nerve impulse transmission.