Scutebarbatolides A-C, new neo-clerodane diterpenoids from Scutellaria barbata D. Don with cytotoxic activity

Abstract Phytochemical investigation of the whole plant of Scutellaria barbata resulted in the isolation of three new neo-clerodane diterpenoids, named scutebarbatolides A-C (1–3), along with six known analogues as 14-deoxy-11,12-didehydroandrographolide (4), scutehenanine H (5), 14β-hydroxyscutolide K (6), scutebata O (7), scutebartines H (8) and I (9). Their structures were elucidated by spectroscopic analyses, including 1D and 2D NMR and mass spectra in comparison with the data reported in the literature. Cytotoxicity of the isolates was evaluated toward five human cancer cell lines, including LNCaP, HepG2, KB, MCF7, and SK-Mel2 cells. Of the isolates, compounds 1 and 6 were shown to have moderate cytotoxicity toward all the cancer cell lines, with IC50 values ranging from 30.8 to 51.1 μM. Our results contribute to more insightful clarification of the use of S. barbata in the prevention and treatment of cancer.