Triterpenoid saponins from Albizia (Mimosaceae) decrease brain tumor cells proliferation

Avicin D, a natural triterpenoid saponin isolated from Acacia victoriae found in Autralia's deserts, inhibits tumor cell growth and induces apoptosis in transformed tumor cell lines in vitro and mouse skin carcinogenesis models in vivo. In order to discover potential new bioactive avicin analogues, ten African Mimosaceae including Albizia, Acacia, and Entada genera were selected to screen their saponins content. Finally, three Albizia species were chosen for their HPLC-DAD, LC-NMR and LC-MS profiles. Saponin enriched-fractions were evaluated for their inhibitory effect on the metabolism of high grade human brain tumor cells. These include the U87 human glioblastoma cell line and glioblastoma cancer stem cells isolated from patients and known to be particularly resistant to chemotherapies. The isolated avicins induce a decrease in the ATP level in the different cell types tested with EC50 values in the range of 3 to 6µg/mL. For some avicins, a differenzial effect could be observed between the stem and non stem cancer cells, the compounds showing higher activity on the cancer cells with stem properties. The specificity of avicins compared to other saponosides has also been evaluated. This study unveils the presence of highly active avicins in African plants and suggests a possible use of these compounds as tools to investigate the pathophysiology of cancer cells and as efficient antitumor agents.