Scubatines A-F, new cytotoxic neo-clerodane diterpenoids from Scutellaria barbata D. Don

Phytochemical investigation of the 70% acetone extract of the whole plant of Scutellaria barbata D. Don afforded six new neo-clerodane diterpenoids, scubatines A-F (1-6), and four known analogues (7-10). Their structures were elucidated on the basis of extensive spectroscopic analyses. Cytotoxic activity against the HL-60 and A549 cell lines was assessed for all isolated compounds. Compound 9 exhibited moderate activity against HL-60 with an IC50 value of 5.6 μM. Compound 6 showed weak cytotoxic activity against A549 and HL-60 with IC50 values of 10.4 and 15.3 μM, respectively.

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