Three
new rearranged diterpenoids, strophioblachins A–C
(1–3), eight new diterpenoids, strophioblachins
D–K (4–11), and seven previously
described diterpenoids (12–18) were
purified from the aerial parts of Strophioblachia fimbricalyx. Compounds 1 and 2 contain a rare 6/6/5/6
ring system, while 3 has an uncommon tricyclo[4.4.0.08,9]tridecane-bridged unit, and their diterpenoid skeletons
are being reported for the first time. Utilizing spectroscopic and
HRESIMS data analysis, the structures of the new compounds (1–11) were established, and ECD and 13C NMR calculations were used to confirm the relative and
absolute configurations of 11 and 9. The
absolute configurations of compounds 1, 3, and 10 were established using single-crystal X-ray
diffraction. The results of testing for anticardiac hypertrophic activity
demonstrated that compounds 10 and 15 dose-dependently
lowered the mRNA expression of Nppa and Nppb. Protein levels were confirmed by Western blotting, which also demonstrated
that compounds 10 and 15 lowered the expression
of the hypertrophic marker ANP. The cytotoxic activity against neonatal
rat cardiomyocytes was assayed in vitro by the CCK-8 and ELISA methods,
and the results showed that compounds 10 and 15 were only very weakly active in the range.