Deheiculatins A-L, 20-oxygenated cembranoids from Macaranga deheiculata

Cembrane diterpenoids: Chemistry and pharmacological activities

Cembrane diterpenoids (cembranoids), characterized by a 14-membered carbon ring and wide variety of functional groups, found in marine and terrestrial organisms. Many studies have shown that cembrane diterpenoids have cytotoxic and anti-inflammatory activities and are widely used in the development of new drugs. This review covered publications from 2011 to 2022 and classified the cembrane-type diterpenoids into isopropyl (ene) type, γ-lactone or unsaturated five-membered ring, δ-lactone or unsaturated six-membered ring, ε-lactone or unsaturated seven-membered ring, and other cembrane diterpenes. In addition, the biological activity and structure-activity relationship were summarized. This will provide guidance for new cembrane-type diterpenes as lead compounds to explore their potential application for treating cancer and inflammatory diseases.

Rapid Construction of the Scaffold of Quorumolide A Enabled by a Tandem ROM/RCM Strategy and a Tandem Oxidative Cyclization Strategy

A synthetically challenging framework in the plant-derived cembranoid quorumolide A was established in a seven-step sequence featuring a ring-opening/-closing metathesis cascade reaction to construct the fused butenolide ring and the 14-membered macroring in a single step. The utilization of a tandem oxidative cyclization strategy is the key to build the tetrahydro-2H-pyran moiety.

Cytotoxic phenolic compounds isolated from the fruits of Macaranga denticulata

A new modified geranylated flavonoid, 3'-dehydroxy-solophenol C (1), along with 17 known compounds (2-18) were isolated from the fruits of Macaranga denticulata. Their structures were established by spectral analysis, such as mass spectrometry, 1D-NMR and 2D-NMR. The new geranylated flavonoid 1 showed a moderate cytotoxic activity against the A549 cell line with IC₅₀ value of 16.0 µM. Compound 9 showed the highest cytotoxic activities against KB, HepG2, Lu-1 and MCF7 cell lines with IC₅₀ values of 0.6, 0.8, 1.3 and 1.2 µM, respectively.

Diterpenoids of terrestrial origin

This review covers the isolation and chemistry of diterpenoids from terrestrial sources from 2017.

Hypoglycemic triterpenes from Gynostemma pentaphyllum

To search for bioactive gypenosides and their analogues, a saponin enriched fraction and its hydrolyzate from Gynostemma pentaphyllum were phytochemically investigated. Fractionation by diverse chromatographic methods, including HPLC, Sephadex LH-20, silica gel, and C18 reverse phase silica gel, led to the isolation and purification of twelve triterpenes, including five undescribed and seven known. The chemical structures of all compounds were determined as analyzed by nuclear magnetic resonance (NMR), high resolution mass spectrometry (HR-MS), infrared spectrum (IR), optical rotation, and chemical transformations. Among all isolates, nine compounds possessed a rare dammarane triterpenoid framework with A-ring modified. The relative configurations of three compounds were determined by 2D NMR for the first time. The absolute configurations of four compounds were determined by the modified Mosher's method. Two of all isolated compounds significantly enhanced 2-deoxy-2-[(7-nitro-2,1,3-benzoxadiazol-4-yl)amino]-D-glucose (2-NBDG) uptake and Glucose Transporter 4 (GLUT4) translocation via activating the AMP-activated protein kinase (AMPK) and acetyl-CoA carboxylase (ACC) signaling pathway. This study provided the potential candidates for the development of antidiabetic agents.

Bioactive diterpenoids from Croton laevigatus

Eight previously undescribed diterpenoids, crolaevinoids A-H, including two halimanes, four clerodanes, and two laevinanes, along with six known analogues were isolated from the twigs of Croton laevigatus. The structures of the previously undescribed were elucidated by spectroscopic analysis, and their absolute configurations were determined by combination of a single crystal X-ray diffraction and CD analysis (exciton chirality and Rh₂(OCOCF₃)₄-induced methods). Crolaevinoids A and B represent the first halimane diterpenoids with a unique lactone bridge between C-12 and C-17. All compounds were evaluated for their inhibitory effects on the nitric oxide (NO) production induced by lipopolysaccharide (LPS) in RAW264.7 macrophage cells. Furocrotinsulolide A and 3,4,15,16-diepoxy-cleroda-13(16),14-diene-12,17-olide exhibited pronounced inhibition of NO production with IC₅₀ values of 10.4 ± 0.8 and 6.0 ± 1.0 μM, respectively, being more potent than the positive control, quercetin (IC₅₀ = 13.1 ± 1.9 μM).