The present article reviewed the
biological activities and possible dental application of three major
polyphenols, i.e.,
lignin-
carbohydrate complexes,
tannins, and
flavonoids, citing mostly our in vitro studies together with those from other groups. All these
polyphenols showed much lower
tumor-selective cytotoxicity against
oral squamous cell carcinoma cells vs. normal oral cells (gingival fibroblast, pulp cell, periodontal ligament fibroblast), in comparison to popular chemotherapeutic
antitumor drugs. Several compounds showing higher
tumor-selectivity did not induce internucleosomal DNA fragmentation, a biochemical hallmark of apoptosis, in oral
carcinoma cell lines.
Lignin-
carbohydrate complex protected the cells from the cytopathic effects of
HIV infection and UV irradiation more efficiently than other
polyphenols. Limited digestion of
lignin-
carbohydrate complex suggests that the
lignin moiety is involved in the prominent anti-HIV activity, whereas the
carbohydrate moiety may function in immunopotentiating activity through a
cell surface receptor. Alkaline extract of plant leaf, which contains higher amounts of
lignin-
carbohydrate complex, showed potent anti-inflammatory action against IL-1β-stimulated human gingival fibroblasts. Local application of
lignin-
carbohydrate complex through oral mucosa is recommended, considering its poor intestinal absorption.