Structurally Diverse Diterpenoids from Sandwithia guyanensis

Bioassay-guided fractionation of
an EtOAc extract of the trunk
bark of Sandwithia guyanensis, using
a chikungunya virus (CHIKV)-cell-based assay, afforded 17 new diterpenoids 1–17 and the known jatrointelones A and
C (18 and 19). The new compounds included
two tetranorditerpenoids 1 and 2, a trinorditerpenoid 3, euphoractines P-W (4–11), and euphactine G (13) possessing the rare 5/6/7/3
(4–7), 5/6/6/4 (8–11), and 5/6/8 (13) fused ring skeletons, sikkimenoid
E (12), and jatrointelones J-M (14–17) possessing jatropholane and lathyrane carbon skeletons,
respectively. Jatrointelones J (14) and M (17) represent the first naturally occurring examples of C-15 nonoxidized
lathyrane-type diterpenoids. The structures of the new compounds were
elucidated by NMR spectroscopic data analysis. The relative configuration
of compound 16 and the absolute configurations of compounds 3–6 and 14 were determined
by single-crystal X-ray diffraction analysis. In addition, jatrointelone
K (15) was chemically transformed to euphoractine T (8) supporting the biosynthetic relationships between the two
types of diterpenoids. Only compound 15 showed a moderate
anti-CHIKV activity with an EC50 value of 14 μM.
Finally, using a molecular networking-based dereplication strategy,
several close analogues of 12-O-tetradecanoylphorbol-13-acetate
(TPA), one of the most potent inhibitors of CHIKV replication, were
dereplicated.