Quercetin-Bromelain Complex, provided by Douglas Laboratories®, is a unique formulation of quercetin, buffered vitamin C, and bromelain. Quercetin is a bioflavonoid that has excellent antioxidant activity.  Magnesium ascorbate is a buffered form of vitamin C, a key antioxidant, which synergistically supports the quercetin activity.  Bromelain is a proteolytic enzyme purified from pineapple, which is active and stable at the acidic levels found in the stomach.