Antitumour plants. Part 6. Novel modified germacranolides and other constituents of Eremanthus elaeagnus Schultz-bip (compositae)

Abstract

Extracts of the stem parts of the woody Composite Eremanthus elaeganus yielded lupeol acetate (1 ), friedelin (Z), epifriedelinol (3). a mixture of sitosterols, the flavonoids tamarixetin (3,5,7,3'-tetrahydroxy-4'-methoxyflavone), genkwanin (5,4'-dihydroxy-7-methoxyflavone),and luteolin 7-methyl ether (5,3',4'-trihydroxy-7-methoxyflavone), and the three novel modified germacranolides eremantholide A ( 5 ) . B (6), and C (minor component) ( 7 ) . The structures of eremantholides A and B were determined by X-ray crystallography, and a crystallographic comparison between the two structures is given. Eremantholide A reacts with propane-I -thiol by a novel 1.6-Michael-type addition which may simulate the mode of its cytotoxic action.

Microbial Transformation of Sesquiterpene Lactones by the Fungi Cunninghamella echinulata and Rhizopus oryzae

“…Biogenesis of 13 in plants, by reductive cyclization of the corresponding 8R-angelate, was proposed previously, 14,15 along the same line of an earlier hypothesis about the biosynthesis of closely related structures called eremantholides A and B. 16 However, apart from the joint occurrence of 5 and 13 in plants of the Lychnophora, Piptolepis, and Proteopsis genera, 17 no other evidence confirming the biogenesis of 13 has been reported so far. Transformation of 5 into 13 by Cunninghamella lends experimental support to the above-mentioned biogenetic hypothesis.…”

“…High-resolution NMR data for 16 are included in the Experimental Section, to facilitate further differentiation from its C-11 epimer (12). Previously, (-)-dehydrocostuslactone (4) and (+)-mokko lactone (16) were chemically correlated with (-)-R-santonin, 20 whose absolute stereochemistry was determined by X-ray analysis. 21 Thus, the absolute configuration of 17 was established as shown.…”

Quantitative HPLC analysis of sesquiterpene lactones and determination of chemotypes in Eremanthus seidelii MacLeish & Schumacher (Asteraceae)

“…Thus, any influence of environmental or developmental factors on the contents of 1 and 2 were excluded by the facts that neighboring trees can belong to different clusters, and that there are no seasonal variations in SL concentrations. Additionally, 1 (a goyazensolide type SL) is a biosynthetic precursor for 2 (a eremantholide type SL), 3 which reveals genetic conditions to produce both SL in the plants studied. Therefore, the difference possibly remains in a differential activity of the enzymes that cyclisation 1 to 2.…”

“…1,2 Previous phytochemical investigations with this genus led to the isolation of flavonoids, triterpenes, poliacetylenes and revealed sesquiterpene lactones (SL) as the main secondary metabolites. 3-9 Some of the SL isolated from the Eremanthus genus posses important biological activities, 3,[6][7][8]10 like the antiproliferative effects on some cancer cell lines 11 and the modulation of the inflammatory process in vitro, by inhibiting the NF-κβ transcriptor factor. 12 Seasonal, 13-16 circadian [17][18][19] and populational 20-24 variations in the content of almost all classes of secondary metabolites, including SL, [25][26][27][28][29] were reported.…”

Complete assignments of NMR data and assessment of trypanocidal activity of new eremantholide C derivatives

“…that were collected in Minas Gerais, Brazil, as previously described (Saúde et al 1998, Ferrari et al 2013. Its structural characterization is described elsewhere (Le Quesne et al 1978, Saúde et al 1998, Saúde-Guimarães et al 2007). 1',2'-Epoxyeremantholide C (2) was prepared by reaction of 1 (2.9 mmol) with m-chloroperbenzoic acid (5.3 mmol) in 50 mL of anhydrous CHCl 3 .…”