Abietane diterpenoids and a sesquiterpene pyridine alkaloid from Euonymus lutchuensis

Recent Developments with Icetexane Natural Products

Icetexane diterpenoids are a diverse family of natural products sourced from several species of terrestrial plants. Icetexanes exhibit a broad array of biological activities and together with their complex 6-7-6 tricyclic scaffolds, they have piqued the interest of synthetic organic chemists, natural products chemists, and biological investigators over the past four decades and were reviewed 13 years ago. This review summarizes icetexane natural products isolated since 2009, provides an overview of new synthetic approaches to the icetexane problem, and proposes an additional classification of icetexanes based on novel structures that are unlike previously isolated materials.

Biologically Active Diterpenoids in the Clerodendrum Genus—A Review

One of the key areas of interest in pharmacognosy is that of the diterpenoids; many studies have been performed to identify new sources, their optimal isolation and biological properties. An important source of abietane-, pimarane-, clerodane-type diterpenoids and their derivatives are the members of the genus Clerodendrum, of the Lamiaceae. Due to their diverse chemical nature, and the type of plant material, a range of extraction techniques are needed with various temperatures, solvent types and extraction times, as well as the use of an ultrasound bath. The diterpenoids isolated from Clerodendrum demonstrate a range of cytotoxic, anti-proliferative, antibacterial, anti-parasitic and anti-inflammatory activities. This review describes the various biological activities of the diterpenoids isolated so far from species of Clerodendrum with the indication of the most active ones, as well as those from other plant sources, taking into account their structure in terms of their activity, and summarises the methods for their extraction.

Diterpenoids from Zhumeria majdae roots as potential heat shock protein 90 (HSP90) modulators

Four undescribed and 17 known diterpenoids were isolated from the roots of Zhumeria majdae Rech.f. & Wendelbo. Using 1D and 2D NMR spectroscopy, ECD spectroscopy, and HRESIMS data analysis, the structures of the undescribed compounds were elucidated. The anti-proliferative activity of isolated compounds was evaluated against HeLa and MCF7 cancer cell lines. The binding affinity of all compounds to HSP90, one of the targets for the modern anticancer therapy, was investigated using surface plasmon resonance. The results demonstrated that lanugon Q interacted with the chaperone. To explain its mechanism of action, experimental and computational tests were also conducted.

Antiprotozoal activity of diterpenoids isolated from Zhumeria majdae- absolute configuration by circular dichroism

PURPOSE

Zhumeria majdae, a unique species of the Zhumeria genus, is an endemic Iranian plant in the Lamiaceae family. Phytochemical investigation and biological activity of this plant are rarely reported. The current study aimed to find new antiprotozoal compounds from the roots of Z. majdae and to determine the absolute configuration of isolated compounds by circular dichroism.

METHODS

The extraction process from roots and aerial parts of Z. majdae was carried out by hexane, ethyl acetate and methanol followed by testing their antiprotozoal effects against Leishmania donovani, Trypanosoma brucei rhodesiense, T. cruzi, and Plasmodium falciparum, respectively. Structure elucidation was done using 1D and 2D NMR spectroscopy and HREIMS spectrometry. In addition, experimental and theoretical circular dichroism spectroscopy was used to establish absolute configuration.

RESULTS

In comparison with aerial parts, the hexane extract from roots showed superior activity against T. b. rhodesiense, L. donovani and P. falciparum with IC₅₀ values of 5.4, 1.6 and 2.1 μg/ml, respectively. From eight abietane-type diterpenoids identified in roots, six were reported for the first time in the genus Zhumeria. 11,14-dihydroxy-8,11,13-abietatrien-7-one (6) exhibited a promising biological activity against P. falciparum (IC₅₀ 8.65 μM), with a selectivity index (SI) of 4.6, and lanugon Q (8) showed an IC₅₀ value of 0.13 μM and SI of 15.4 against T. b. rhodesiense.

CONCLUSION

Altogether, according to the results, of 8 isolated compounds, dihydroxy-8,11,13-abietatrien-7-one (6) and lanugon Q (8) exhibited a promising activity against T. b. rhodesiense and P. falciparum. In conclusion, these compounds could be potential candidates for further analysis and may serve as lead compounds for the synthesis of antiprotozoal agents. Graphical abstract.

Diversity oriented multi-component reaction (DOS-MCR) approach to access natural product analogues: regio- and chemo-selective synthesis of polyheterocyclic scaffolds via one-pot cascade reactions

Skeletally diverse and complex aza-cyclopenta(cd)diindene, pyrrolo(3,4-d)pyridine-13-carboxamide, and furo-pyrrolo(1,2-a)imidazole-4-carboxamide fused polyheterocyclic hybrid scaffolds and a furo(2,3-b)furan core have been accessed via one-pot three-component reaction by exploiting the build/couple/pair strategy of diversity oriented synthesis (DOS). This protocol is metal free, has a good substrate scope and affords products with good to excellent yields and regio- and chemo-selectivity. The heterocyclic skeletons obtained in this study mimic natural products such as eupolauramine, gracilamine and presilphiperfolanol.

Abietane diterpenoids from Caryopteris incana (Thunb.) Miq

Twelve new diterpenes, caryopincaolide A-L (1-4, 11-12, 16-19, 27-28), together with twenty-eight known diterpenes, have been isolated from the whole plant of Caryopteris incana (Thunb.) Miq. Their structures were elucidated on the basis of 1D and 2D NMR, IR, X-ray crystal diffraction and mass spectroscopic data, as well as ECD calculations. All compounds were tested for in vitro dipeptidyl peptidase IV (DPP-IV) inhibitory activity, with compounds 3, 4, 28, 29, and 40 exhibiting DPP-IV inhibitory effects with IC50 values ranging from 54.2 to 228.9 μM. Compounds 1, 3 and 4 also showed potent activity toward the inhibition of the growth of human cancer cells and 1 can induce apoptosis in Hey and A-549 cells.

Bioactive Diterpenoids from Clerodendrum kiangsiense

A new abeo-abietane diterpenoid, 12-methoxy-6,11,14,16-tetrahydroxy-17(15→16)-abeo-5,8,11,13-abietatetraen-3,7-dione (8), was isolated from the hydroalcoholic extract of the herb of Clerodendrum kiangsiense along with seven known diterpenoids (1–7). Their structures were identified on the basis of spectroscopic analyses including two-dimensional NMR and comparison with literature data. All of these compounds were evaluated for their cytotoxic activities against the growth of human cancer cells lines HL-60, SMMC-7721, A-549 and MCF-7 by the MTT assay. The results showed that cryptojaponol (4), fortunin E (6) and 8 exhibited significant cytotoxicity against four human cancer cell lines.

Denhaminols A-H, dihydro-β-agarofurans from the endemic Australian rainforest plant Denhamia celastroides

Eight new dihydro-β-agarofurans, denhaminols A-H (1-8), were isolated from the leaves of the Australian rainforest tree Denhamia celastroides. The chemical structures of 1-8 were elucidated following analysis of 1D/2D NMR and MS data. The absolute configuration of denhaminol A (1) was determined by single-crystal X-ray crystallography. All compounds were evaluated for cytotoxic activity against the human prostate cancer cell line LNCaP, using live-cell imaging and metabolic assays. Denhaminols A (1) and G (7) were also tested for their effects on the lipid content of LNCaP cells. This is the first report of secondary metabolites from D. celastroides.

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 2013 is reviewed.

Four-component bicyclization approaches to skeletally diverse pyrazolo[3,4-b]pyridine derivatives

A novel four-component bicyclization strategy has been established, allowing a flexible and practical approach to 37 examples of multicyclic pyrazolo[3,4-b]pyridines from low-cost and readily accessible arylglyoxals, pyrazol-5-amines, aromatic amines, 4-hydroxy-6-methyl-2H-pyran-2-one, and cyclohexane-1,3-diones. The polysubstituted cyclopenta[d]pyrazolo[3,4-b]pyridines were stereoselectively synthesized through a microwave-assisted special [3+2+1]/[3+2] bicyclization with good control of the spatial configuration of exocyclic double bonds. The novel [3+2+1]/[2+2+1] bicyclization resulted in 17 examples of unreported pyrazolo[3,4-b]pyrrolo[4,3,2-de]quinolones. Reasonable mechanisms for forming two new types of multicyclic pyrazolo[3,4-b]pyridines are also proposed.