The glycosidic composition of Psolus phantapus was studied for the first time. Two new glycosides, phantapusosides A (1) and B (2), and the known psolusoside P (3) were isolated and their structures were established by analysis of 1H, 13C NMR, 1D TOCSY, and 2D NMR (1H,1H COSY, HMBC, HSQC, ROESY), and HR-ESI mass spectra. These compounds are structurally close to those isolated from other representatives of the genus Psolus: P. fabricii, P. peronii and P. chitonoides. These data confirm the chemotaxonomic significance of triterpene glycosides of sea cucumbers, demonstrating that closely related species biosynthesize structurally similar metabolites. The cytotoxic activity of compounds 1 and 2 was studied against four human breast cancer cell lines (MCF-7, T-47D, MDA-MB-231, MDA-MB-468), as well as the non-tumorigenic mammary epithelial cell line MCF-10A and the pancreatic epithelioid carcinoma cell line PANC-1. The glycosides were selectively active against the TNBC cell lines MDA-MB-231 and MDA-MB-468. Notably, both glycosides inhibited the clonogenic potential of TNBC cell lines more significantly than their metabolic activity (MTT assay) and demonstrated a more pronounced colony-inhibiting effect toward the basal-like cell line MDA-MB-468, making this cell line a promising model for future investigation of the antitumor effects of glycosides.
Silchenko et al. (Mon,) studied this question.