Studies on anti-cancer activities of sesquiterpene lactons from yacon(Smallanthus sonchifolius) leaves

Abstract

Since 1970, cancer has been holding the first place of the mortality rate in Japan. Causes of cancer are considered to be related to aging, lifestyle and other environmental conditions. From now on, cancer is a severe health problem because cancer mortality rate would be rapidly increased among an aging Japanese society.

In our previous study, Sesquiterpene Lactones (SLs) isolated from yacon leaf such as enhydrin, uvedalin and sonchifolin exhibited an anticancer promoter activity coupled with TPA-induced deformation of Raji cells. Furthermore, the SLs showed cytotoxicity against HeLa cell, which was caused by inducted of apoptosis as a consequence of caspase-3/7 activation. In this study, dimeric SLs, enhydrofolin (5) and uvedafolin (6), from yacon leaf were newly found in the extract and also exhibited cytotoxicity in HeLa, HL60 and B16 cell lines.

Dimeric SLs (IC₅₀ 5; 1.69 and 6; 1.93 μM, respectively) are found to be the most effective substances among 8 SLs and typical cancer drug, etoposide (IC₅₀ 3.2 μM) on HeLa cells. Common functional group of these SLs for the activity-structure relationship was 1) the a-methylene-g-lactone, 2) the ester linkage of Dimeric SL between two sets of SL monomers, and 3) the acetyl group at the C-9 for the great cytotoxicity.