Cytotoxic ent-kaurane diterpenoids from Isodon wikstroemioides

Cirsitakaoside isolated from Premna szemaoensis reduces LPS-induced inflammatory responses in vitro and in vivo

Cirsitakaoside is a natural compound isolated from Premna szemaoensis. However, the anti-inflammatory effects of cirsitakaoside are poorly understood. We investigated the anti-inflammatory action of cirsitakaoside in lipopolysaccharide (LPS)-stimulated macrophages and mice in vivo. Cirsitakaoside could suppress the production of pro-inflammatory cytokines such as interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) in a dose-dependent manner in LPS-stimulated mouse peritoneal macrophages and RAW264.7 cells. Cirsitakaoside also could inhibit inducible nitric oxide synthase (iNOS) mRNA and cyclooxygenase-2 (COX-2) mRNA expression in LPS-stimulated mouse peritoneal macrophages and RAW264.7 cells. These effects were partially carried out by inactivated nuclear factor-κB (NF-κB) and Mitogen-activated protein kinases (MAPKs) pathway via inhibiting the phosphorylation of the IKKα/β, IκBα and c-Jun N-terminal kinase/stress-activated protein kinase (JNK) in LPS-stimulated murine macrophages. In vivo, we showed that cirsitakaoside could relieve LPS-induced inflammation response. These results suggest that cirsitakaoside has the potential anti-inflammatory effect for treatment of inflammation diseases.

Synthesis of a new allelopathic agent from the biotransformation of ent-15α-hydroxy-16-kauren-19-oic acid with Fusarium proliferatum

The use of kaurane diterpenes as substrates in fungal biotransformation to achieve bioactive compounds has been widely reported. In this work, the natural product kaurenoic acid, a diterpene widely distributed in the plant Kingdom, was chemically converted into ent-15α-hydroxy-kaur-16-en-19-oic acid (1). Substrate 1 was subjected to biotransformation by the fungus Fusarium proliferatum, furnishing a new derivative, ent-2α,15α-dihydroxy-kaur-16-en-19-oic acid (2). The structure of metabolite 2 was deduced on the basis of spectroscopy and MS data. Derivative 2 showed allelopathic activity on germination and growth of root and stem of lettuce (Lactuca sativa), inhibiting 100% of germination and growth of roots and stem, at higher concentration assayed (10-4 mol/L).

Bioactive ent-kaurane diterpenoids from Isodon rubescens

Seven previously undescribed 7,20-epoxy-ent-kaurane diterpenoids, isojiangrubesins A-G, along with seventeen known ones, were isolated from the aerial parts of Isodon rubescens. Their structures were characterized on the basis of spectroscopic methods and signal-crystal X-ray diffraction. All of these compounds were evaluated for their in vitro cytotoxicity against five human tumor cell lines (HL-60, SMMC-7721, A-549, MCF-7, and SW480). Four isolates exhibited significant inhibitory ability against all cell lines, with IC₅₀ values ranging from 0.5 to 6.5 μM; They also strongly inhibited NO production in LPS-stimulated RAW264.7 cells.

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.

Structurally Diverse Diterpenoids from Isodon scoparius and Their Bioactivity

Fourteen new diterpenoids (1-14) based on four skeletal types and two known analogues (15 and 16) were isolated from the aerial parts of Isodon scoparius. Compound 2 is the first ent-kaurane diterpenoid featuring a 1,11-ether bridge, and the structures of these new compounds were established mainly by NMR and MS methods. The absolute configurations of 1 and 5 and the relative configuration of 3 were determined using single-crystal X-ray diffraction. The absolute configuration of 14 was determined by comparison of the experimental and calculated electronic circular dichroism spectra. Compounds 1, 4, and 15 were active against five human tumor cell lines (HL-60, SMMC-7721, A-549, MCF-7, and SW-480), and they also inhibited NO production in LPS-stimulated RAW264.7 cells, with IC₅₀ values of 1.0, 3.1, and 1.8 μM, respectively.

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.

Bioactive Enmein-Type ent-Kaurane Diterpenoids from Isodon phyllostachys

Thirty-two enmein-type ent-kaurane diterpenoids, including 13 new compounds, were isolated from the aerial parts of Isodon phyllostachys. Compounds 1 and 2 are the first examples of 3,20:6,20-diepoxyenmein-type ent-kauranoids, and the structures of these new compounds were established mainly by analyzing NMR and HREIMS data. The absolute configurations of 1 and 8 and the relative configuration of 9 were determined using single-crystal X-ray diffraction. Compounds 11, 15, 20, and 21 were active against five human cancer cell lines (HL-60, SMMC-7721, A-549, MCF-7, and SW-480), with IC50 values ranging from 1.2 to 5.0 μM. Compounds 3, 11, 15, 17, 20, 21, 25, and 29 strongly inhibited NO production in LPS-stimulated RAW264.7 cells, with IC50 values ranging from 0.74 to 4.93 μM.

A new flavone C-glycoside and a new bibenzyl from Bulbophyllum retusiusculum

A new flavone C-glycoside, apigenin 6-C-α-arabinofuranosyl 8-C-α-arabinopyranoside (1) and a new bibenzyl, bulbotetusine (2), were isolated from the tubers of Bulbophyllum retusiusculum. Their structures were established on the basis of extensive spectroscopic analyses. The absolute configuration of 2 was determined by the comparison of experimental and calculated electronic circular dichroism. Compounds 1 and 2 showed no obvious cytotoxic activity against any five human tumour cell lines with IC50 values >40 μM.

Three New Cytotoxic ent-Kaurane Diterpenes from Isodon excisoides

Three types of ent-kaurane diterpenoids were isolated from the aerial parts of Isodon excisoides, including three new diterpenoids, 1α,7α,14β-trihydroxy-20-acetoxy-ent-kaur-15-one (1); 1α,7α,14β,18-tetrahydroxy-20-acetoxy-ent-kaur-15-one (2); and 1α-acetoxy-14β-hydroxy-7α,20-epoxy-ent-kaur-16-en-15-one (3); together with six known diterpenes henryin (4); kamebanin (5); reniformin C (6); kamebacetal A (7); kamebacetal B (8); and oridonin (9). The structures of the isolated compounds were elucidated by means of nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry in conjunction with published data for their analogs, as well as their fragmentation patterns. Compounds 5 and 9 were isolated from Isodon excisoides for the first time. To explore the structure-activity relationships of the isolated compounds, they were tested for their cytotoxic effects against five human cancer cell lines: HCT-116, HepG2, A2780, NCI-H1650, and BGC-823. Most of the isolated compounds showed certain cytotoxic activity against the five cancer cell lines with IC50 values ranging from 1.09-8.53 µM. Among the tested compounds, compound 4 exhibited the strongest cytotoxic activity in the tested cell lines, with IC50 values ranging from 1.31-2.07 µM. Compounds 1, 6, and 7 exhibited selective cytotoxic activity.

Six new cytotoxic and anti-inflammatory 11, 20-epoxy-ent-kaurane diterpenoids from Isodon wikstroemioides

The present study was designed to determine the chemical constituents of EtOAc extracts of the aerial parts of Isodon wikstroemioides. Compounds 1-8 were isolated and purified by normal-phase silica gel and reversed-phase C18silica gel column chromatography and HPLC. Their structures were elucidated by extensive spectroscopic methods. Most of them were evaluated for their in vitro cytotoxicity against human cancer HL-60, SMMC-7721, A-549, MCF-7, and SW-480 cells and their inhibitory activity against nitric oxide (NO) production in LPS-activated RAW264.7 macrophages. Among the eight 11, 20-epoxy-ent-kauranoids isolated, compounds 1-6 (isowikstroemins H-M) were new diterpenoids. Compounds 1, 3, and 7 exhibited significant cytotoxicity with IC50 values ranging from (0.84 ± 0.02) to (4.09 ± 0.34) μmol · L(-1), while compounds 4 and 5 showed selective cytotoxicity. In addition, compounds 1, 3, 4, and 7 exhibited inhibitory activity against nitric oxide (NO) production in LPS-activated RAW264.7 macrophages. These results provide a basis for future development of these compounds as anti-cancer and anti-inflammatory agents.

Diterpenoids of terrestrial origin

This review covers the isolation and chemistry of diterpenoids from terrestrial as opposed to marine sources and includes, labdanes, clerodanes, pimaranes, abietanes, kauranes, gibberellins, cembranes and their cyclization products. The literature from January to December, 2014 is reviewed.

Enantioselective synthesis of decalin structures with all-carbon quaternary centers via one-pot sequential Cope/Rauhut-Currier reaction

The first example of one-pot sequential Cope/Rauhut-Currier reactions are reported and used to make functionalized decalin structures with all-carbon quaternary stereocenters. The substrates for the new sequential reaction are generated through a six-step sequence including an enantioselective Birch reduction-allylation reaction which makes the overall process asymmetric.