Cytotoxic diterpenoids from Isodon megathyrsus

Bioactive ent-kaurane diterpenoids from Isodon serra

Nine 7,20-epoxy-ent-kaurane diterpenoids (15-acetylmegathyrin B, serrin E, 14β-hydroxyrabdocoestin A, serrin F, serrin G, 11-epi-rabdocoestin A, serrin H, serrin I, and 15-acetylenanderianin N), along with seven known ones, were isolated from the aerial parts of Isodon serra. Their structures were elucidated by extensive spectroscopic analysis, and the absolute configuration of 15-acetylmegathyrin B was determined by signal-crystal X-ray diffraction. All of these compounds were evaluated for their cytotoxic activities against five human tumor cell lines (HL-60, SMMC-7721, A-549, MCF-7, SW480). Serrin F, rabdocoestin B and 1α,11β-dihydroxy-1α,11β-acetonide-7α,20-epoxy-ent-kaur-16-en-15-one showed cytotoxic activities against all cell lines, with IC50 values ranging from 0.7 to 4.6 μM; serrin F also strongly inhibited NO production in LPS-stimulated RAW264.7 cells. Otherwise, 14β-hydroxyrabdocoestin A, serrins H and I, as well as enanderianin N and megathyrin B, also exhibited inhibitory effects towards NO production, while no cytotoxicity against five cell lines was detected.

ent-Kaurane diterpenoids from Isodon japonicus

Five ent-kaurane diterpenoids, 6beta,7beta,14beta-trihydroxy-1alpha,19-diacetoxy-7alpha,20-epoxy- ent-kaur-16-en-15-one (1), 1alpha,6beta,7beta-trihydroxy-11alpha,19-diacetoxy-7alpha,20-epoxy-ent-kaur-16-en-15-one (2), 6-hydroxy-1alpha,19-diacetoxy-6,7-seco-ent-kaur-16-en-15-one-7,20-olide (3), 19-hydroxy-1alpha,6-diacetoxy-6,7-seco- ent-kaur-16-en-15-one-7,20-olide (4), and 6-aldehyde-1alpha,19-diacetoxy-6,7-seco- ent-kaur-16-en-15-one-7,20-olide (5), along with 10 known ent-kaurane diterpenoids, pseurata C (6), longikaurin C (7), effusanin C (8), longikaurin B (9), longikaurin D (10), effusanin D (11), excisanin B (12), lasiokaurin (13), megathyrin A (14), and loxothyrin A (15), were isolated from the aerial parts of Isodon japonicus. Their structures were determined on the basis of spectroscopic (1D-, 2D-NMR and MS) and chemical evidence. The isolates were evaluated for their inhibitory effects on LPS-induced production of nitric oxide in murine macrophage RAW264.7 cells.

Diterpenoids from Isodon species and their biological activities

Isodon species (Labiatae) are widely distributed plants, many of which are used in folk medicine. Over the past twenty years, they have received considerable phytochemical and biological attention. Thestructures of their many diterpenoids constituents, especially those with an ent-kaurane skeleton, have been elucidated. The significant phytochemical and pharmacological diterpenoids form the subject of this review. There are 290 references.

Chemical constituents of Isodon melissoides

Four new diterpenoids, melissoidesin E (1), F (2), G (4) and H (5), together with one known diterpenoid and two lignan glycosides, were isolated from aerial parts of Isodon melissoides. Their structures were established by spectral analysis and comparison with related compounds. The lignan glycosides (compounds 7 and 8) were the first examples to be isolated from the genus Isodon plants.