Group B Oleanane Triterpenoid Extract Containing Soyasaponins I and III from Soy Flour Induces Apoptosis in Hep-G2 Cells

Soyasaponins I and III are monodesmodic oleanane triterpenoids that are thought to be one of the main potentially bioactive saponins found in soy (Glycine max) and related products. An extract that contained a majority of the soyasaponins as I (62%) and III (29%) was studied in a hepatocarcinoma cell line (Hep-G2) to determine the potential cellular bioactivity. The extract was found to inhibit the growth of Hep-G2 cells measured by the MTT viability assay (LC50 0.389 ± 0.02 mg/mL) dose-dependently. Cell death was determined using three distinct flow cytometry assays for apoptosis (sub-G1 cell-cycle analysis and multi-caspase and TUNEL assays), and cellular morphological images were acquired by confocal laser scanning microscopy. All of the apoptotic detection assays were positive for apoptotic cell accumulation. The TUNEL detection assay after 72 h of treatment showed the greatest apoptotic cell accumulation (40.45 ± 4.95%), followed by the multi-caspase assay for 48 h treated cells (6.97 ± 0.14% mid-apoptotic and 12.87 ± 0.81% late apoptotic) and sub-G1 accumulation (17.67 ± 0.42%). The multi-caspase assay indicated that the cellular protein expression of the caspase family of enzymes was the main apoptotic pathway trigger. Confocal laser scanning microscopy further confirmed the induction of apoptosis in Hep-G2 cells. Soyasaponins I and III may contribute to the reported bioactive and chemopreventative properties of soy by the induction of apoptosis.