This provides new information on the structure-activity relationship of flavonoids. Recently we demonstrated that several flavonoids can inhibit the proliferation of certain human thyroid cancer cell lines. Among the flavonoids tested, apigenin and luteolin are the most effective inhibitors of these tumor cell lines. Protein levels of these signaling molecules were not affected. Apigenin may provide a new approach for the treatment of human anaplastic thyroid carcinoma for which no effective therapy is presently available.
Flavonoids display a wide range of pharmacological properties including anti-inflammatory.
A431 cells treated with Lu or Qu exhibited protuberant cytoplasmic blebs and progressive shrinkage morphology. Lu and Qu also time-dependently induced the appearance of a ladder pattern of DNA fragmentation, and this effect was abolished by EGF treatment. The addition of EGF only marginally diminished the inhibitory effect of luteolin and quercetin on the growth rate of A431 cells, treatment of cellular proteins with EGF and luteolin or quercetin greatly reduced protein phosphorylation, indicating Lu and Qu may act effectively to inhibit a wide range of protein kinases, including EGFR tyrosine kinase. Examination of the relationship between the chemical structure and inhibitory effects of eight flavonoids reveal that the double bond between C2 and C3 in ring C and the OH groups on C3 and C4 in ring B are critical for the biological activities. Tea is grown in about 30 countries and, next to water, is the most widely consumed beverage in the world.