Serratene triterpenoids from Phlegmariurus cruentus with cytotoxic activity and their proapoptotic effect

Phlegmariurus cruentus, a member of the Lycopodiaceae family, is a phytochemically unexplored species that is native to the high Andean forests of Colombia and Venezuela. Herein, serratene-type triterpenoids were detected in the ethanol extract of P. cruentus via LC-ESIMS, and subsequent bioassay-guided fractionation performed using the Artemia salina lethality assay yielded four new serratenes (1-4) along with six known analogs (5-10). The structures of the isolated compounds were elucidated by HRESIMS, IR, 1D and 2D NMR spectroscopy, optical rotation, and a comparison with reported data. The in vitro cytotoxic activity of compounds 1-9 against three human cancer cell lines (U87-MG glioblastoma, MCF-7 breast carcinoma, and HT-29 colon adenocarcinoma) was evaluated using the MTT assay. Compounds 1, 5, 7, and 8 exhibited significant cytotoxicity against the U87-MG and MCF-7 cells, with IC₅₀ values ranging from 1.1 ± 0.6 to 9.6 ± 2.6 μM. Notably, compared with the other two cell lines, the U87-MG cells were more sensitive to these compounds. A further flow cytometry investigation revealed that compounds 1, 5, 6, 7, and 8 manifested proapoptotic effects in the U87-MG cells. Additionally, a GC-MS analysis of the less polar chromatographic fraction led to the identification of two know cytotoxic volatiles, α-tocospiro A and α-tocospiro B, which are reported here in the Lycopodiaceae family for the first time. These findings suggest that some compounds from P. cruentus may serve as promising candidates for further anticancer research.