Advances in the chemistry of sesquiterpene lactones

The paper gives a review of the chemistry of natural sesquiterpene lactones.     

Epoxidation of sesquiterpene lactones tourneforin and ludartin

Epoxy derivatives of the sesquiterpene lactones ludartin and tourneforin were synthesized. Their structures were elucidated using spectral data and x-ray structure analysis.     

Dimeric sesquiterpene lactones : Structure of absinthin

Absinthin, a constituent of $\text{A}$. $\text{absinthium}$, has been given structure $\text{2}$.     

Review of the analytical techniques for sesquiterpenes and sesquiterpene lactones

In this paper the analytical techniques of about the last 2 decades for sesquiterpenes including their lactones are reviewed. For sesquiterpenes, methods like GC, GC-EI-MS, GC-CI-MS, GC-MS-MS, GC-FT-IR, GC-UV, GC-AES, 13C-NMR, PY-GC-MS, HPLC, HPLC-TSP, SFE, SFC, SFC-UV are available, GC combined with MS is the most widespread. Sesquiterpene lactones can be analysed by HPLC, HPLC-TSP, HPLC-APCI, HPLC-ESI, HPLC-PB, HPLC-NMR, SFC, MEKC, GC, GC-MS, TLC and OPLC. Here HPLC is the method of choice. The usefulness of the individual methods are briefly discussed.     

Fragmentation of sesquiterpene lactones related to leucomisin

The mass spectra of seven sesquiterpene lactones — leucomisin, austricin, parishin B, parishin C, matricarin, artelin, and artelin diacetate — have been studied. It has been shown that the presence of the conjugated bonds C(1)=C(10), C(2)=0, and C(3)=C(4), and also C(5)=C(6), stabilizes M⁺, and the main fragmentation process is that of the splitting out of the lactone ring. The presence of hydroxy substituents at C(3) and C(8) of the guaiane system does not change the stability of M⁺ under electron impact. The directions of fragmentation have been confirmed by an analysis of spectra obtained by the metastable defocussing of daughter ions and by measuring the accurate masses of the main peaks of the fragmentary ions.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 96–101, January–February, 1987.     

Spatial structures of the sesquiterpene germacrane lactones tanachin and tamirin

An x-ray investigation has been made of the sesquiterpene lactones tanachin and tamarin: diffractometer, CuK-radiation, 845 and 981 reflections, respectively, direct method, R factors 0.064 and 0.065. The conformations of both molecules are boat-boat with configurations of the¹D₁₄ and¹⁵D₅ types.Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Institute of Bioorganic Chemistry, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodynkh Soedinenii, No. 2, pp. 198–204, March–April, 1989.     

Antibacterial and cytotoxic activities of the sesquiterpene lactones cnicin and onopordopicrin

The antimicrobial and cytotoxic activities of chloroform extracts from the weeds Centaurea tweediei and C. diffusa, and the main sesquiterpene lactones isolated from these species, onopordopicrin and cnicin, respectively, were assayed. Results show that the chloroform extracts from both Centaurea species possess antibacterial activities against a panel of Gram-positive and Gram-negative bacteria. Remarkable antibacterial activity against methicillin-resistant Staphylococcus aureus was also measured. Both the extracts and the purified sesquiterpene lactones show high cytotoxicity against human-derived macrophages. Despite this cytotoxicity, C. diffusa chloroform extract and cnicin are attractive candidates for evaluation as antibiotics in topical preparations against skin-associated pathogens.     

Conformational analysis of sesquiterpene lactones of germacrane type

The structure of 1(10)Z,4Z-germacranolides was studied by the method of molecular mechanics. Possible conformers, the probability of their existence, and barriers to conformational transitions were determined. For Part 1, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 268–271, February, 1997.     

Structure of new sesquiterpene lactones from Inula germanica

Summary It has been established that the substance isolated previously fromInula germanica L. is a mixture of two new sesquiterpene lactones: germanin A and germanin B.On the basis of chemical reactions and a study of IR, UV, NMR, and mass spectra, structures (I) and (XVI), respectively, are proposed for germanin A and germanin B.All-Union Scientific-Research Institute of Medicinal Plants. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 578–589, September–October, 1974.     

Antimalarial activity of sesquiterpene lactones from Vernonia cinerea

Two new sesquiterpene lactones, vernolides C and D as well as six known ones were isolated from the dichloromethane fraction of an aqueous extract from Vernonia cinerea. Their structures were elucidated by spectroscopic methods. Among the known sesquiterpene lactones, three of them were described in this plant for the first time. In vitro antiplasmodial evaluation showed that the three major compounds 1, 7 and 8 were active against chloroquine resistant Plasmodium falciparum strain (W2) with IC(50) 3.9, 3.7 and 3.5 microM, respectively.     

Structure of new sesquiterpene lactones from Inula germanica

Chemistry of Natural Compounds - It has been established that the substance isolated previously fromInula germanica L. is a mixture of two new sesquiterpene lactones: germanin A and germanin B. On...     

Three new sesquiterpene lactones from the pericarps of Illicium merrillianum

Structures of three new sesquiterpene lactones 1-3, isolated from the pericarps of Illicium merrillianum, have been assigned as 14-O-benzoylfloridanolide, 2,10-epoxy-3-dehydroxypseudoanisatin and 7-O-methylpseudomajucin on the basis of spectroscopic data and chemical transformation. The structure of 2, having an ether linkage between C-2 and C-10, has been confirmed by X-ray crystallographic analysis.     

Two new sesquiterpene lactones from the leaves of Laurus nobilis

As a part of our ongoing interest in new bioactive compounds from natural sources, we studied Laurus nobilis (Lauraceae). This plant is widespread in the Mediterranean area and is used for medicinal and economic purposes. Chromatographic separations on active extracts led to the isolation of two new sesquiterpene lactones, 5a,9-dimethyl-3-methylene-3,3a,4,5,5a,6,7,8-octahydro-1-oxacyclopenta[c]azulen-2-one (1) and 3beta-chlorodehydrocostuslactone (2). The structures of the new compounds were identified by 1D and 2D NMR experiments, as well as high resolution mass spectrometry. The cytotoxic activity was also evaluated against three different tumor cell lines of human origin.     

Circular dichroism of some sesquiterpene lactones of the germacrane type

The CD spectra of a series of germacranolides have been considered, and the parameters of the Cotton effects observed have been correlated with the stereochemistries of the compounds studied. The applicability for germanocranolides of the Waddell-Stocklin-Geissman rule is discussed.Deceased.Institute of the Chemistry of Plant Substances of the Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 176–179, March–April, 1986.     

Gaigranin and gaigrandin — New sesquiterpene lactones fromGaillardia grandiflora

Two new sesquiterpene lactones — gaigranin and gaigrandin — have been isolated from the epigeal part ofGaillardia grandiflora, and their structures have been established on the basis of spectral (IR, PMR,¹³C NMR, and mass) characteristics and x-ray structural analysis.Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 79–85, January–February, 1995. Original article submitted October 7, 1994.     

Rhaposerine and rhaserolide, new sesquiterpene lactones fromRhaponticum serratuloides

Two new crystalline guaianolides,viz., rhaposerine and rhaserolide, were isolated from an ethanolic extract of the above-ground part of the plantRhaponticum serratuloides by column chromatography along with sesquiterpene lactones,viz., centaurepensin and acroptilin, which have been found in other plants. The chemical structures of the title lactones were established by¹H and¹³C NMR spectroscopy and 2D¹H−¹H (COSY) and¹³C−¹H (COSY and COLOC) NMR spectroscopy. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2010–2014, October, 1999.     

Two new sesquiterpene lactones from the fruits of Illicium jiadifengpi

Two new seco-prezizaane-type sesquiterpenes, 3,4-dehydroneomajucin (1) and 1,2,3,4-tetradehydroneomajucin (2), were isolated from the fruits of Illicium jiadifengpi. The structure of these compounds was determined using 1D and 2D NMR and ESI-MS. The isolates were evaluated for their anti-hepatitis B virus activities on the Hep G2.2.15 cell line. The inhibitory rates of compounds 1 and 2 on the HBeAg and HBsAg expression were 30.08 ± 3.09% and 11.43 ± 1.92% at a concentrations of 68.00 μM and 7.88 ± 1.21% and 16.96 ± 4.24% at a concentration of 68.50 μM, respectively.     

Grandulin and grandicin—New sesquiterpene lactones fromInula grandis

Chemistry of Natural Compounds -