Novel steroidal glycosides from the underground parts of Agapanthus africanus and their cytotoxicity against human cancer cell lines

Approximately 25% of all new anticancer agents approved by the Food and Drug Administration between January 1981 and September 2019 were derived from natural products and their derivatives, suggesting that natural products continue to play a crucial role in the development of anticancer agents [ 1 ]. As part of our ongoing phytochemical investigations to discover new candidates for anticancer agents from higher plants, we have focused on Agapanthus africanus . Previous studies have reported that this plant contains chalcone and dimeric dihydrochalcone derivatives and a steroidal glycoside [ 2 ] [ 3 ]. However, our literature survey has demonstrated that the chemical constituents of A. africanus remain to be fully investigated, prompting us to perform a comprehensive phytochemical investigation of this plant. Sixteen novel steroidal glycosides ( 1–16 ) were isolated, and their structures were determined primarily by NMR spectroscopic analysis ([ Fig. 1 ]). The cytotoxicity of 1–16 against SBC-3 human-small cell lung cancer cells was evaluated, exhibiting IC 50 values ranging from 1.2 to 35 μM. Compound 1 , which showed the most potent cytotoxicity among the isolated compounds, was evaluated for its apoptosis-inducing activity in SBC-3 cells. As a result, 1 arrested the cell cycle at the G2/M phase and induced apoptosis, accompanied by depolarization of mitochondrial membrane potential, overproduction of reactive oxygen species, and a decreased Bcl-2/Bax ratio. These phenomena indicate that 1 induces apoptosis via an intrinsic pathway in SBC-3 cells. Compound 1 represents a promising seed compound for the development of novel anticancer agents targeting small-cell lung cancer. Fig. 1 Structures of 1 - 16 Publication History Article published online: 05 March 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany