Petromaroside A, an unprecedented natural nucleoside from the sponge Petrosia sp. with potent cytotoxicity and biosynthetic insight.

A chemical investigation of the marine sponge Petrosia sp. led to the isolation of a novel nucleoside, petromaroside A (1), featuring an unprecedented C-5' hydroxymethylated deoxyribose moiety, along with thymidine (2). These structures and their absolute configurations were elucidated by comprehensive spectroscopic analyses and quantum chemical calculations, including NMR, HRESIMS, LC-MS/MS, GIAO-NMR calculations, and DP4+ probability analysis. Notably, this discovery establishes sponge Petrosia sp. as the first known natural source of nucleosides bearing a C-5' hydroxymethylated deoxyribose unit, while thymidine (2) is reported for the first time from the genus Petrosia. A plausible biosynthetic pathway is proposed for petromaroside A (1), in which its formation is suggested to originate from a common precursor derived via condensation between l-aspartate and carbamoyl phosphate. Compound 1 exhibited potent cytotoxic activity against a panel of human cancer cell lines (HeLa, MCF-7, Hep-G2, and HT-29), with IC50 values ranging from 0.5 ± 0.1 to 1.7 ± 0.3 µM, whereas thymidine (2) showed no significant activity. These findings identify petromaroside A as a promising scaffold for future mechanistic, biosynthetic, and synthetic investigations aimed at the development of structurally novel nucleoside-based anticancer agents.