Polyphenols as a chemopreventive agent in oral carcinogenesis: putative mechanisms of action using in-vitro and in-vivo test systems.

Polyphenols are present in foods and beverages, being related to sensorial qualities such as color, bitterness, and astringency, which are relevant in products such as wine, tea, and grape juice. These compounds occur naturally in forms varying from simple phenolic acids to complex polymerized tannins. Oral cancer is the most common head and neck cancer, and it often has a poor prognosis owing to local tumor invasion and frequent lymph node metastasis.