Litoarbolide A: an undescribed sesquiterpenoid from the Red Sea soft coral with an anti-malarial activity evaluation.

Soft corals distributed across the Red Sea coasts are a rich source of diverse and bioactive natural products. Chemical probing of the Red Sea soft coral led to isolation and structural characterization of an undescribed sesquiterpenoid, litoarbolide (), along with 14 previously reported metabolites (). The chemical structures of the isolates were assigned based on NMR as well as high resolution electrospray ionization mass spectrometry (HR-ESI-MS) data. Litoarbolide A is supposed to be the biosynthetic precursor to other sesquiterpenoids, which formed further post-translational modifications. Furthermore, these metabolites were evaluated for anti-malarial activity, where only the acyclic sesquiterpenoid of a -germacrane nucleus () showed an activity against chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of with IC at 3.7 and 2.2 mg/mL, respectively. Moreover, the isolated metabolites were all non-toxic to the Vero cell line. These findings support the consideration of in further natural anti-malarial studies.