Kazuki Mori, Yoshihiro Ayano, Yoshitomo Hamada, Taichi Hojima, Ryuta Tanaka, Yusuke Higashino, Mayu Izuno, Taisuke Okamoto, Takashi Kawasaki, Masahiro Hamada, Noriyuki Nakajima and Akiko Saito
Flavan-3-ol, which is primarily found in tea, is able to inhibit the proliferation of the human cancer cell line HeLa S3; in this study, we investigate the importance of the 2,3-cis structure in this inhibition. We synthesized six (−)-epicatechin and (+)-catechin analogs modified with a galloyl moiety at either the 3-hydroxyl, 5-hydroxyl, or 3,5-dihydroxyl positions. We then investigated their biological activity, DPPH radical scavenging activity and inhibitory activity on HeLa S3 cell proliferation. Among the six compounds, (−)-epicatechin-3,5-O-digallate showed the strongest inhibitory activity on HeLa S3 cell proliferation, whereas (+)-catechin-3,5-O-digallate was not active. In addition, there is no relation among the cell proliferation inhibitory activity and DPPH radical scavenging activity. Furthermore non-specific BSA binding ability of synthesized compounds was demonstrated. Improved photoaffinity beads method revealed that there is no difference between (−)-epicatechin-3,5-O-digallate and (+)-catechin-3,5-O-digallate on the non-specific BSA absorption. These data indicated that the 2,3-cis structure of flavan-3-ol is essential for the inhibition of HeLa S3 cell proliferation