New bioactive pyrrole alkaloid isolated from the Saudi Red Sea sponge Stylissa carteri with potential anticancer property against human lung adenocarcinoma cell line, and possible mechanisms

Chemical investigation of a MeOH extract of the Red Sea sponge Stylissa carteri, offered a new bromopyrrole alkaloid named stylisinone (1) along with other eight pyrrole alkaloids. The structures were established by comprehensive spectroscopic analyses of NMR and MS, as well as by comparison with the literature. The in vitro anticancer activity of the isolated alkaloids was evaluated against human cancer cell lines, HepG2, MCF-7, LS513, A549, and THP1, and BM as normal mice cells. The results showed that stylisinone had the highest cytotoxicity against the A549 cell line, with IC50 values at 24.08 µM, respectively. The new metabolite stylisinone caused strong cell cycle arrest at sub G1 and G2/M (22.43-fold and 2.28-fold, respectively), indicating its potential as an antitumor agent. Furthermore, stylisinone showed a marked increase in Annexin V-FITC necrotic cells (from 1.23 to 21.38%), making this molecule an attractive candidate for further mechanism of action studies.