Sesquiterpenoids from Incarvillea arguta: absolute configuration and biological evaluation

Dimeric eremophilane-type sesquiterpenoids from the peeled stems of Syringa pinnatifolia

A continued phytochemical investigation guided by 1H NMR and LC-MS data on the ethanol extract from the peeled stems of Syringa pinnatifolia Hemsl. led to the isolation of 16 undescribed dimeric eremophilane sesquiterpenoids, namely syringenes R-Z (1-9) and A1-G1 (10-16). These structures were elucidated by extensive analysis of spectroscopic data, including HRESIMS, NMR, quantum-mechanics-based computational analysis of NMR chemical shifts, and single-crystal X-ray diffraction analyses, and a concise rule for determination of relative configuration of angular methyl was proposed. The results of the cardioprotective assay demonstrated that 3 exhibits a protective effect against hypoxia-induced injuries in H9c2 cells. This effect was observed at a concentration of 10 μM, with a protective rate of 28.43 ± 11.80%.

Syringenes M - Q, Eremophilane Sesquiterpenoid Dimers from the Peeled Stems of Syringa pinnatifolia

As a part of systematic studies on Syringa pinnatifolia, a continued phytochemical investigation guided by ¹ H-NMR and LC/MS data on the ethanol extract afforded five new dimeric eremophilane sesquiterpenoids, namely syringenes M-Q (1-5). These structures were elucidated by extensive analysis of spectroscopic data, including infrared (IR), high-resolution electrospray ionization mass spectrometry (HR-ESI-MS), nuclear magnetic resonance (NMR), quantum-mechanics-based computational analysis of NMR chemical shifts, and single-crystal X-ray diffraction. Compounds 4 and 5 showed inhibitory activities against NO production induced by lipopolysaccharide in RAW264.7 macrophage cells, with IC₅₀ values of 5.1 and 9.3 μM, compared to positive control indomethacin (IC₅₀ 33.6 μM). These dimeric eremophilane sesquiterpenoids may be potential markers for discriminating this species from the genus Syringa and the Oleaceae family.

Natural disesquiterpenoids: an update

This review highlights the progress on the isolation, bioactivity, biogenesis and total synthesis of dimeric sesquiterpenoids since 2010.

Nicotabaflavonoidglycoside, the first example of cembranoid and flavonoid heterodimer from Nicotiana tabacum

Nicotabaflavonoidglycoside (1), a novel cembrane-type diterpenoid and flavonoid heterodimer had been isolated from the leaves of Nicotiana tabacum. Its structure was elucidated as (1″S, 6″S) or (1″R, 6″R)-8-[6″-((-)-(1″S, 2″E, 4″Z, 7″E, 11″E)-cembra-2″, 4″, 7″, 11″-tetraenyl)]-rutin by comprehensive analyses of the NMR and HRESIMS spectra. Its absolute configurations of C-1″ and C-6″ were assigned as (1″S, 6″S) by its biogenesis and electronic circular dichroism (ECD). A possible biogenesis involving eliminate reaction of (1S, 2E, 4S, 6R, 7E, 11E)-2, 7, 11-cembratriene-4, 6-diol or its 4R isomer, as well as electrophilic substitution reaction of rutin was postulated.

A new phenylethanoid glycoside from Incarvillea compacta

A new phenylethanoid glycoside, 3'''-O-methylcampneoside I (1), was isolated from the 90% ethanolic extract of the roots of Incarvillea compacta, together with three known compounds, campneoside I (2), ilicifolioside A (3), and campneoside II (4). Their structures were determined spectroscopically and compared with previously reported spectral data. Compound 1 existed as epimers and displayed better 1,1-diphenyl-2-picrylhydrazyl (DPPH)-free radical scavenging activity using di-tert-butyl-4-methylphenol (BHT) as the positive control. In addition, pretreatment of human HepG2 cells with compound 1 significantly increased the viability on CCl4-induced cell death.

Natural sesquiterpenoids

This review covers the isolation, structural determination, synthesis and chemical and microbiological transformations of natural sesquiterpenoids. The literature from January to December 2012 is reviewed, and 471 references are cited.

Terpecurcumins A-I from the rhizomes of Curcuma longa: absolute configuration and cytotoxic activity

Terpecurcumins A-I (1-9), together with three known analogues (10-12), were isolated from the rhizomes of Curcuma longa (turmeric). They were derived from the hybridization of curcuminoids and bisabolanes. The structures and absolute configurations of 1-9 were elucidated on the basis of extensive spectroscopic data analysis, including NMR and electronic circular dichroism spectra. The configuration of 10 was further confirmed by X-ray crystallography. A plausible biogenetic relationship for 1-12 is proposed. Compounds 4, 6, 7, 10, and 11 showed higher cytotoxic activities (IC(50), 10.3-19.4 μM) than curcumin (IC(50), 31.3-49.2 μM) against human cancer cell lines (A549, HepG2, and MDA-MB-231).