Isorosthornins A-C, new ent-kaurane diterpenoids from Isodon rosthornii

Diterpenoids from Isodon species: an update

Covering: December 2005 to June 2016. Previous review: Nat. Prod. Rep., 2006, 23, 673-698Over the last decade, great efforts have been made to conduct phytochemistry research on the genus Isodon, which have led to the isolation and identification of a number of diterpenoids. At the same time, these newly reported diterpenoids with diverse structures have led to new findings on their biological functions and chemical synthesis research. In this update, we review more than 600 new diterpenoids, including their structures, classifications, biogenetic pathways, bioactivities, and chemical synthesis.

Four new diterpenoids from Isodon eriocalyx var. laxiflora

Four new diterpenoids, laxiflorins S-V (1–4), bearing four different types, and one known compound, laxiflorin O (5), were isolated from Isodon eriocalyx var. laxiflora. Compound 1 was the first example of ent-kauranoids bearing a unique C₂₄ carbon framework and compound 4 was the first example of 3,4-seco-ent-abietane diterpenoids from the Isodon genus. Their structures were determined by spectroscopic methods (UV, IR, MS, NMR).

Bioactive ent-kaurane diterpenoids from Isodon rosthornii

Isorosthin A (1), the first 20-nor-enmein-type diterpenoid, and 15 new ent-kauranoids, isorosthins B-P (2-16), along with 22 known analogues were isolated from the aerial parts of Isodon rosthornii. The structures of 1-16 were elucidated by means of spectroscopic analysis. The relative configuration of 2 and the absolute configuration of 3 were determined by single-crystal X-ray diffraction. Cytotoxicity evaluation against five human tumor lines showed inhibitory effects by several of the compounds tested. Furthermore, 12 of the isolates exhibited inhibitory activity against nitric oxide production in LPS-activated RAW264.7 macrophages.