Minor diterpenoids from Scutellaria galericulata

Abstract Three new neo-clerodane diterpenoids, one C-16 epimeric pair, scutegalerins C and D, and scutegalerin E, together with the known scutaltisin B, were isolated from the acetone extract of the aerial parts of Scutellaria galericulata . The chemical structures of the new compounds were elucidated by spectroscopic techniques and a comparison with data of similar compounds as (13 S ,16 R ,19 S )-6α-acetoxy-2α,19;4α,18;15,16-triepoxy-16,19-dimethoxy-neo-clerodane (scutegalerin C), (13 S ,16 S ,19 S )-6α-acetoxy-2α,19;4α,18;15,16-triepoxy-16,19-dimethoxy-neo-clerodane (scutegalerin D) and (11 S ,13 R ,16 S ,19 S )-6α - acetoxy - 2α,19;4α,18;11,16;15,16-tetraepoxy-19-methoxy-neo-clerodan-3β-ol (scutegalerin E). Detailed NMR spectra of scutaltisin B were included to rationalize the new assignments in the 1 H NMR spectrum and the correction of some of the previously reported carbon signals in the 13 C NMR spectrum for the isolated mixture of the two C-11 epimers scutaltisin B and scutaltisin C.