(Tea flavor, color and astringency are in part due to the condensation of the catechins to form the bright orange-red pigment thalami.) Researchers believe that catechin is effective because it easily sticks to proteins, blocking bacteria from adhering to cell walls and disrupting their ability to destroy them. Viruses have hooks on their surfaces and can attach to cell walls. The catechin in green tea prevents viruses from adhering and causing harm. Catechin reacts with toxins created by harmful bacteria and harmful metals such as lead, mercury, chrome and cadmium.