Abstract
The major component of green tea tannin, (-) -epigallocatechin gallate (EGCg), has been found to exhibit bio-antimutagenicity in certain bacterial strains or anti-tumor-promoting activity in certain cultured cells. Based on these findings, EGCg and crude catechins (those extracted from green tea and composed mainly of EGCg) were given to animals to see if these test compounds could prevent the growth of inoculated tumors. Tumor cells were inoculated into mice or rats either intraperitoneally (i. p.) to grow ascites tumors or subcutaneously (s. c.) to grow solid tumors. The results showed that both EGCg and crude catechins exhibited appreciable effects when administered (i. p. or s. c.) to the animals after s. c. inoculation of the tumors. No life-prolongation effect was observed among the animals with ascites tumors. Oral administration of crude catechins before tumor inoculation appeared to strengthen the effect of i. p. administration after the inoculation. Furthermore, long-term feeding of crude catechins to mice suppressed the growth of inoculated tumor cells. Moreover, the effect of s. c. administration of crude catechins was clearly enhanced by i. p. injection of lipopolysaccharide (LPS) afterwards, suggesting the induction of a TNF-like substance. From the results of the above experiments, it was assumed that EGCg and crude catechins might suppress the growth of inoculated tumor cells in animals through potentiation of immunological mechanisms rather than working directly on proliferating tumor cells.
