Background: Securidaca 1 is a triterpenoid saponin fraction obtained from African medicinal plant S. longipedunculata, whose action activated apoptosis via inhibition of PI3K-AKT downstream. Preliminary studies show an IC50 of 7.03 (μg/mL), with RT-qPCR gene expression revealing a fold-change reduction of MCL-1 and BCL2L1 antiapoptotic proteins, as well as the inhibition of AKT-3, VEGFA, and CDH-1. Therefore, considering the role of PI3K-AKT pathway in tumoral resistance of ovarian cancer and epithelial-mesenchymal transition during development, our major aim was to isolate and identify the components of securidaca 1 responsible for the activity.

Experimental Procedure: Freeze-dried sample of securidaca 1 was fractionated by FLASH chromatography (RP-C18) and the resultant fractions screened by SRB cytotoxicity assay (96-well format) using HeLa cell line. The most promising subfraction was further purified by semipreparative HPLC (reversed-phase). Isolated substances were identified by HR-ESI-MS and IC50s determined and compared with 5-fluorouracil (5-FU) reference standard.

Results: The HR-ESI-MS spectrum under negative ion mode revealed the parent molecular ion peaks of the semipreparative fractions (FR15-6 and FR15-7), whose IC50s were confirmed at 3.84 and 4.83 μg/mL, respectively, on HeLa cell line, more sensitive than 5-FU. MS/MS fragmentation spectra (negative ion mode) show putative fragments of molecular ions 455 and 425 (m/z), respectively, typically indicating oleanine triterpenoid aglycone. Post-TLC derivatization tested positive to Liebermann Burckhard and Carr Price reactions, and sugars.

Conclusion: FR15-6 and FR15-7 are potential candidates for anticancer development whose actions may be responsible for antitumor activities previously seen in securidaca 1. Work is ongoing to evaluate their capacities in blocking tumor development via antiapoptotic effectors of PI3K-AKT downstream pathway.

Note: This abstract was not presented at the conference.

Citation Format: Titus Chukwuemeka Obasi, Radu Oprean. HR-ESI-MS identification of novel triterpenoid antitumor substances in securidaca 1, using activity-guided SRB assay [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research; 2019 Sep 13-16, 2019; Atlanta, GA. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(13_Suppl):Abstract nr A58.