Tannins are polymeric phenolic substances capable of precipitating gelatinous compounds from solution. Many human physiological activities, such as stimulation of phagocytic cell, host-mediated tumor activity, and a wide range of anti-infective actions, have been assigned to tannins. Thus, their mode of antimicrobial action, as described in the section on quinones may be related to their ability to inactivate microbial adhesins, enzymes, cell envelope transport proteins, etc. The antimicrobial significance if this paticular activity has not been explored.