Sweetpotato leaves (Ipomoea batatas L.) contain a high content of polyphenolics that consist of
caffeic acid,
chlorogenic acid,
3,4-di-O-caffeoylquinic acid,
3,5-di-O-caffeoylquinic acid, 4,5-di-O-caffeoylquinic
acid, and 3,4,5-tri-O-caffeoylquinic
acid. We investigated the suppression of the proliferation of selected human
cancer cells by phenolic compounds isolated from sweetpotato leaf. The human
cancer cells used in this research included a
stomach cancer (Kato III), a
colon cancer (DLD-1), and a promyelocytic
leukemia cell (HL-60).
Caffeic acid and di- and tricaffeoylquinic
acids dose-dependently depressed
cancer cell proliferation, and the difference in sensitivity between
caffeoylquinic acid derivatives and each kind of
cancer cell was observed. Specifically, 3,4,5-tri-O-caffeoylquinic
acid effectively depressed the growth of three kinds of
cancer cells, and
caffeic acid had an exceptionally higher effect against HL-60 cells than other di- and tricaffeoylquinic
acids. In attempting to clarify the mechanism of growth suppression with the addition of the apoptotic inhibitor
N-ethylmaleimide, we observed that the nuclear granulation in 3,4,5-tri-O-caffeoylquinic
acid-treated HL-60 cells suggested apoptosis induction. This effect was confirmed by DNA fragmentation, an increase of
caspase-3 activity, and expression of c-Jun. Growth suppression of HL-60 cells by 3,4,5-tri-O-caffeoylquinic
acid was determined to be the result of apoptotic death of the cells. These results indicate that 3,4,5-tri-O-caffeoylquinic
acid may have potential for
cancer prevention.