Argymekosides A-C, Three Undescribed 21α-Hydroxyoleanolic Acid Glycosides From Argyreia mekongensis and Their Cytotoxic Activity.

Three previously undescribed 21α-hydroxyoleanolic acid glycosides, designated Argymekosides A-C (1-3), together with eight known compounds (4-11), were isolated from the aerial parts of Argyreia mekongensis Gagnep. & Courchet. Their structures were elucidated by comprehensive spectroscopic analyses, including HRESIMS and 1D and 2D nuclear magnetic resonance (NMR) spectroscopy, as well as comparison with published data. The absolute configurations of three new compounds were determined by electronic circular dichroism (ECD) calculations. The isolated compounds were evaluated for their cytotoxic activities against HepG2, MCF-7, and SK-LU-1 human cancer cell lines. Compound 5 exhibited potent cytotoxicity toward all three cell lines, with IC50 values of 5.06, 5.70, and 5.79 µM, respectively. Compound 4 displayed moderate cytotoxic activity against all tested cell lines (IC50 = 26.73-35.53 µM), whereas compound 6 showed weak activity against HepG2 (IC50 = 72.03 µM) and MCF-7 cells (IC50 = 91.51 µM). The remaining compounds were inactive, with IC50 values exceeding 100 µM.