Discovery of a heat-generated compound DHD derived from water extract with inhibitory effects on colon cancer cells viability and migration.

The plant Juss. (PV) has long been used as a medicinal herb for treating intestinal disorders. Pharmacological activities such as anti-oxidation, anti-inflammation, and anti-cancer effects of compounds isolated from PV have been reported, but these bioactive compounds were not derived from PV water extract (PVW). Therefore, in the present study, we aimed to identify the active component(s) of PVW which exhibit inhibitory activities in colon cancer cells viability and migration. Human colon cancer HCT116 cells were treated with the isolated compounds of PVW and then subjected to MTT and transwell migration assays. Our results showed that an active compound in PVW, 8,9-didehydro-7-hydroxydolichodial (DHD) inhibited cell viability of HCT116 cells, with IC value at 6.1 ± 2.2 μM. Interestingly, DHD was not detected in the herbal material of PV. Further investigation revealed that DHD is in fact a heat-generated compound derived from a natural compound present in PV, namely valerosidate. Valerosidate also reduced cell viability in HCT116 cells, with IC value at 22.2 ± 1.1 μM. Moreover, both DHD (2.75 μM) and valerosidate (10.81 μM) suppressed cell migration in HCT116 cells, with inhibitory rates at 74.8% and 74.6%, respectively. In addition, western blot results showed that DHD (5.5 μM) could significantly increase p53 expression by 34.8% and PTEN expression by 13.9%, while valerosidate (21.6 μM) could increase expressions of p53 and PTEN by 26.1% and 34.6%, respectively in HCT116 cells after 48 h treatment. Taken together, this is the first report that a naturally-occurring valerosidate present in PV could actually transform to DHD by thermal hydrolysis, and both compounds exhibited inhibitory effects on cell viability and migration in HCT116 cells via increasing the expressions of tumor suppressors (p53 and PTEN). Our findings demonstrated that valerosidate is present in raw herb PV but not in PVW, while DHD is present in PVW rather than in raw herb PV. This difference in chemical profiles of raw herb and boiled water extract of PV may affect the anti-cancer activity, and hence further investigations are warranted.