If the product is all-natural, what is the ingredient that makes teeth white in the Extra Whitening formula?

Rather than use synthetic, harsh bleaching chemicals which can harm the tooth enamel, our whitening formulas use two natural Enzymes. Bromelain, derived from the Stems of Pineapples, and Papain, derived from the Papaya. These Enzymes gently remove foreign material from the surface of the teeth which can cause discoloration.