New sesquiterpene lactones from Inula oculus-christi L.

Investigation of the aerial parts of Inula oculus-christi L. led to the identification of four new sesquiterpene lactones: an eudesmanolide (4α,15α-epoxypulchellin E) and three guaianolides (2α-acetoxy-4α,9β-dihydroxy-1β-guaia-11(13),10(14)-dien-12,8α-olide, 9β,10β-epoxygaillardin, 9α,10α-epoxy-2-epi-gaillardin), in addition to the known gaillardin, pulchellin E, pulchellin C and 3-O-palmitates of 16β-hydroxylupeol, 16β-hydroxy-β-amyrin, and faradiol. The structures of all compounds have been elucidated on the basis of their spectral data.     

Two sesquiterpene lactones from artemisia species

Two new sesquiterpene lactones, himeyoshin and montanone, were isolated from Artemisia feddei and A. montana, respectively and identified by chemical and spectral data as1α,2α-epoxy-3-oxo-5,6-dihydroalantolactone and 1,10-dihydro-11,13-dehydromatricarin.     

Antiproliferative and apoptotic sesquiterpene lactones from Carpesium faberi

Four new (1-4) and 13 known (5-17) sesquiterpene lactones along with two known diterpenes (18, 19) were isolated from the whole plant of Carpesium faberi. The new structures were elucidated by means of spectroscopic techniques and some chemical transformations to be pseudoguaian-1α(H)-8α,12-olide-4β-O-β-d-glucopyranoside (1), 4β,10α-dihydroxy-5α(H)-1,11(13)-guaidien-8α,12-olide (2), 4β,10β-dihydroxy-5α(H)-1, 11(13)-guaidien-8β,12-olide (3), and (4S)-acetyloxyl-11(13)-carabren-8β,12-olide (4). All isolates were tested against MCF-7 human breast cancer cells using the MTT assay. Among them, the sesquiterpene lactones (except tomentosin 17) possessing an α-methylene-γ-lactone moiety were found to have in vitro antiproliferative activities, with IC₅₀ values of 3.0-38.8 μg/mL. The effects of four selected sesquiterpene lactones (guaianolide 2, carabranolide 4, pseudoguaianolide 9, eudesmanolide 13) on the cell cycle were examined using flow cytometry (FCM).     

New sesquiterpene lactones from Inula species

An investigation of Inula helenium, I. royleana, I. salicina and I. bifrons afforded in addition to known sesquiterpene lactones 20 new lactones, the eudesmanolides 3, 6 and 8–12, the germacranolides 14–18 and 20–22, the guaianolides 23 and 25, the pseudoguaianolide 26, the xanthanolides 28 and 32 and the cyclopropane analogue 30. Structures and configurations of these new compounds were established by extensive PMR studies and by some chemical transformations. Some of the investigated species contain besides the widely distributed pentaynene 33 several known thymol derivatives together with a new one (40).     

Cytotoxic sesquiterpene lactones from Artemisia anomala

Two new sesquiterpene lactones, 8α-acetoxy-1,10α-epoxy-2-oxo-guaia-3,11(13)-dien-12,6α-olide (1) and 13-acetoxy-1-oxo-4α-hydroxy-eudesman-2(11)-dien-12,6α-olide (2), along with six known analogs (3-8), were isolated from the whole plant of Artemisia anomala S. Moore. Their structures were elucidated by extensive analysis of spectroscopic data. Compounds 6 and 7 exhibited in vitro moderate cytotoxicity against A549 cells with IC₅₀ values of 0.6 and 0.9 μM, and HepG2 cells with IC₅₀ values of 5.4 and 3.0 μM, respectively.     

Sesquiterpene lactones of Podanthus mitiqui

Ovatifolin and two new sesquiterpene lactones, deacetylovatifolin and arturin (1β-hydroxy-8β-angeloyloxy-eudesmane-4(15),11(13)-diene-6α,12-olide, have been isolated from stems and leaves of Podanthus mitiqui. Two of these compounds showed cytotoxic activity.     

Koanolides B-D,new sesquiterpene lactones from Koanophyllon gibbosum

Three new germacrane-type sesquiterpene lactones, koanolides B–D (1-3) have been isolated from the aerial parts of Koanophyllon gibbosum (Asteraceae), along with the previously reported sesquiterpene lactone koanolide A and the flavonoid eupatorin. The structures of the new compounds were elucidated using spectroscopic and spectrometric data analyses, including 1D and 2D NMR, and by comparison with known spectral data. The antiproliferative activities of the new compounds were evaluated in a panel of six representative human solid tumor cell lines and showed GI₅₀ values ranging from 1.3 to 16 μM for the new molecules.     

Systematic implications of sesquiterpene lactones in the subtribe melampodiinae

Within the tribe Heliantheae of the Asteraceae, the genetic boundaries of the subtribe Melampodinae have recently been drastically revised by Stuessy. The number of genera within the subtribe has been reduced and new generic groupings have been established. The present study correlates the distribution of sesquiterpene lactones found in these genera with the newly revised subtribal boundaries. The genera Acanthospermum, Melampodium, Polymnia and Sigesbeckia produce predominantly melampolide-type sequiterpene lactones. Limited chemical data support Stuessy's removal of the genera Desmanthodium, Clibadium and Ichthyothere from the subtribe Melampodiinae. The occurrence of melampolide-type sesquiterpene lactones in members of the genera Tetragonotheca (Helianthinae) and Enhydra (Ecliptinae) indicate a possible position of these genera in the Melampodiinae.     

Anti-inflammatory sesquiterpene lactones from the flower of Vernonia cinerea

Bioassay-guided fractionation of the hexane extract from the flowers of Vernonia cinerea (Asteraceae) led to the isolation of a new sesquiterpene lactone, 8α-hydroxyhirsutinolide (2), and a new naturally occurring derivative, 8α-hydroxyl-1-O-methylhirsutinolide (3), along with seven known compounds (1 and 4-9). The structures of the new compounds were determined by 1D and 2D NMR experiments and by comparison with the structure of compound 1, whose relative stereochemistry was determined by X-ray analysis. The isolated compounds were evaluated for their cancer chemopreventive potential based on their ability to inhibit nitric oxide (NO) production and tumor necrosis factor alpha (TNF-α)-induced NF-κB activity. Compounds 1, 2, 4, 5, and 9 inhibited TNF-α-induced NF-κB activity with IC(50) values of 3.1, 1.9, 0.6, 5.2, and 1.6μM, respectively; compounds 4 and 6-9 exhibited significant NO inhibitory activity with IC(50) values of 2.0, 1.5, 1.2, 2.7, and 2.4μM, respectively.     

New melampolide sesquiterpene lactones from Melampodium leucanthum

The isolation of five germacranolide sesquiterpene lactones from Melampodium leucanthum Torrey and Gray (Compositae-Heliantheae) is reported. The structures of three new melampolides, melampodin-A acetate, leucanthin-A and leucanthin-B, have been determined by spectral methods and chemical correlations.     

Antifungal activity of sesquiterpene lactones

Forty-five sesquiterpene lactones were screened for their antifungal activities against Microsporum cookei, Trichophyton mentagrophytes and Fusarium sp. The screening tests showed that a majority of sesquiterpene examined possess at least weak antifungal activity, the eudesmanolides being the most active. The antifungal activity of sesquiterpene lactones cannot be explained by the presence or absence of two potential active sites (the exocyclic methylene and, in pseudoguaianolides, a β-unsubstituted cyclopentenonel) but other functions must play a role in enhancing or reducing this activity.     

New sesquiterpene lactones from Liriodendron tulipifera

Four new sesquiterpene lactones were obtained from L. tulipifera; two germacranolides, lipiferolide (4) and epitulipinolide diepoxide (5) from the leaves, an elemanolide, epitulipdienolide (7), and an eudesmanolide, γ-liriodenolide (6) from the root bark. Structural determination was by physical and chemical methods and by direct correlation to the known epitulipinolide (3). Lipiferolide and epitulipinolide diepoxide possess cytotoxic activity against KB cells.     

Two sesquiterpene lactones from Trichogonia gardneri

The structures and stereochemistries of two sesquiterpene lactones from Trichogonia gardneri were established as (6R,7S,8S,9S,IOR)-4E-9,10-dihydroxy-8-tigloxygermacr-4-en-6,12-olide) and (5R*,6R*,7S*,8S*,9R*)-14-acetoxy-3-chloro-9-hydroxy-2-oxo-8-tigloxyguia-1(10),3-dien-6,12-of olide by a combination of NMR spectrometry and X-ray diffraction. The results show that the structures of several sesquiterpene lactones which were isolated previously from related species require revision.     

Four new sesquiterpene polyol esters from Celastrus angulatus

Celastrus species, such as Celastrus angulatus, has been demonstrated to be very rich in natural sesquiterpene polyol esters sharing the β-dihydroagarofuran skeleton, some of which showed various biological activities. In this paper, four new sesquiterpene polyol esters, named as angulatins K-N (1–4), along with three known ones, 1β-acetoxy-9β-benzoxy-4α, 6α-dihydroxy-8α, 15-diisobutanoyloxy-2β-(α-methyl)-butanoyloxy-β-dihydroagarofuran, angulatin A, and celangulin III, were isolated from the root bark of C. angulatus. The structures of the new compounds were elucidated by extensive spectroscopic methods, mainly including HR-MS and 1D and 2D NMR techniques.     

Further sesquiterpene lactones from Helianthus maximiliani

By using HPLC, a new melampolide, a known heliangolide and three known germacrolides were isolated as minor constituents from a north central Texas population of Helianthus maximiliani. In an earlier report, we identified the germacrolide desacetyleupaserrin as the principal sesquiterpene lactone from this population.     

Three bourbonenolides and other sesquiterpene lactones from two vernonia species

A re-investigation of V. arkansana afforded several new sesquiterpene lactones, three bourbonenolides, obviously closely related to those isolated from this plant previously, a glaucolide and a methoxy derivative most probably formed by fragmentation of the corresponding bourbonenolide. From V. profuga in addition to known lactones a new guaianolide was isolated. The biogenetic relationships of the Vernonia sesquiterpene lactones are discussed briefly.     

Anticancer sesquiterpene lactones of Michelia compressa (magnoliaceae)

Investigation of the cytotoxic active components of Michelia compressa afforded two new cytotoxic sesquiterpene lactones, michelenolide and micheliolide. Parthenolide, costunolide, santamarine, reynosin and liriodenine were also isolated and exhibited cytotoxic activity. The known sesquiterpene lactones, lanuginolide and dihydroparthenolide, were isolated but were not active. Two other new inactive sesquiterpene lactones, compressanolide and dihydroreynosin, were also obtained. The structures of michelenolide and micheliolide were confirmed by partial synthesis from parthenolide and the structure of compressanolide by partial synthesis from dihydroparthenolide.     

Supercritical fluid extraction assisted isolation of sesquiterpene lactones with antiproliferative effects from Centipeda minima

Pseudoguaianolide sesquiterpene lactones minimolides A (1), B (2), C (3) and D (4) and two guaianolide sesquiterpene lactones minimolides E (5) and F (6), along with seven known ones (7–13), were isolated from the supercritical fluid extract of Centipeda minima. The structures of these compounds were elucidated by extensive spectroscopic methods (IR, UV, HRESIMS, 1D-NMR and 2D-NMR), and the complete structure and stereochemistry of 1 was further confirmed by X-ray diffraction analysis. Compounds 1, 5–8, 11 and 13 displayed inhibitory activity against human nasopharyngeal cancer cells (CNE) with IC₅₀ values ranging from 1.1 to 20.3 μM. Compound 13 containing both α-methylene-γ-lactone and α, β-unsaturated cyclopentenone moieties exhibited even stronger inhibitory activity than that of cisplatin (positive control) through cell cycle arrest at G2/M phase. Isolation of six sesquiterpene lactones from Centipeda minima highlighted the potential of supercritical fluid extraction for enrichment of minor constituents for phytochemical study.     

Pungent sesquiterpene lactones of the european liverworts Chiloscyphus polyanthus and Diplophyllum albicans

The characteristic pungency of the European liverwort, Chiloscyphus polyanthus, is due to a mixture of four sesquiterpene lactones, two new structures ent-5β-hydroxydiplophyllin and ent-3-oxodiplophyllin, and the previously known diplophyllin and diplophyllolide. A new dihydrodiplophyllin, together with the pungent diplophyllolide and diplophyllin, has been isolated from Diplophyllum albicans. Ent-dihydrodiplophyllolides derived from the above pungent diplophyllolides produce intense numbness of the tongue. All pungent sesquiterpene lactones showed inhibitory activity towards the germination and root elongation of rice husks.     

Stereostructures of inunal and isoalloalantolactone,two biologically active sesquiterpene lactones from Inula racemosa

Two new sesquiterpene lactones, inunal and isoalloalantolactone, have been isolated from Inula racemosa. Inunal, an aldehydolactone, displays considerable biological activity as a plant growth regulator. Structures have been assigned to these compounds on the basis of spectral data and chemical correlation with alantolactone and isotelekin.