Three oxygenated alantolides from Inula racemosa

Goyal, Rita; Chhabra, B. R.; Kalsi, P. S.

doi:10.1016/0031-9422(90)83069-d

Cited by 30 publications

(17 citation statements)

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“…The chemical shift (CS) of the angular methyl on C-10 of the major component of 6 was 1.03 ppm whereas that of the minor one shifted to weaker field to 1.16 ppm. This is comparable with data for α-and β-epoxyisotelekin [10]. Thus, the major component was assumed to have the α-orientation of the oxirane O atom; the minor, the β-orientation, based on the literature data and the NMR spectra.…”

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confidence: 91%

“…The PMR and 13 C NMR spectra of 6a and 6b were very similar (Tables 1 and 2). Epoxidation of the lactone telekin, which has a similar structure, is known to form the α-epoxide as the main product and the β-epoxide as the minor one [10]. The chemical shift (CS) of the angular methyl on C-10 of the major component of 6 was 1.03 ppm whereas that of the minor one shifted to weaker field to 1.16 ppm.…”

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confidence: 98%

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Acidic isomerization of alantolactone derivatives

2006

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A series of derivatives of the natural sesquiterpene lactones alantolactone (1) and isoalantolactone (2) was prepared. The α-methylene-γ-lactone moiety was retained in the structures of these for further modifications using reactions that affected exclusively the nonconjugated double bonds of the decalin ring.The great potential biological and pharmacological activities of natural sesquiterpene lactones are responsible for the interest in developing this area of chemistry [1,2]. The most promising direction is the chemical modification of compounds isolated from natural sources in order to prepare substances with new properties. Certain natural sesquiterpene lactones have been used as effective medicinal preparations (for example, the antitumor preparation Arglabin [3]).The goal of the present work was to prepare a series of derivatives based on the natural sesquiterpene lactones alantolactone (1) and isoalantolactone (2) in the structures of which the α-methylene-γ-lactone moiety was retained for further modifications. This was achieved using reactions that affected exclusively the nonconjugated double bonds of the decalin ring.A mixture of lactones 1 and 2 (~1:1 ratio) was isolated from roots of Inula helenium L. (Asteraceae) by a method consisting of extraction of the ground raw material with CHCl 3 and subsequent chromatography over a column of SiO 2 . Fractions containing this mixture were evaporated and crystallized (2-3 times) from aqueous CH 3 OH (70%) to afford about 25% (of the total content of the extract) of pure 2. The isomers were further separated over a column of SiO 2 impregnated with AgNO 3 (5%) with gradient elution by benzene in light petroleum ether. The compounds isolated by chromatography over the column impregnated with Ag contained an impurity of Ag (2-5% according to elemental analysis) that was removed by passing their benzene solution over a layer of neutral Al 2 O 3 (activity I). The resulting compounds were identical to those in the literature [4].It is well known that olefins can undergo acidic isomerization to form intermediates and transition-state carbonium ions in which prototropic and skeletal rearrangements are observed. Therefore, we investigated the reactions of the alantolactone derivatives with acids.Alantolactone (1) is stable to acids (under drastic conditions the reaction mixture polymerizes) according to the literature [5] and our data.Shifts of the exocyclic double bond in the decalin ring of 2 that occur in the presence of acids have been reported [6]. This formed a mixture of the thermodynamically more favorable isomeric trisubstituted olefins that contain an endocyclic double bond between C-4 and C-5 (3) or C-3 and C-4. The ratio of products depends on the acid used (2:1 for methanesulfonic acid in trifluoroethanol [5] and 1:3 in formic acid [7]). We found the conditions for selective isomerization of 2 into 3. The PMR spectrum of 3 contained a singlet for the methyl on the double bond (1.60 ppm) instead of signals for the exomethylene protons on C-15. The 13 C NMR...

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Acidic isomerization of alantolactone derivatives

2006

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“…f. is a traditional medicinal plant that has long been used in China, India and Europe. Previous phytochemical investigations into this plant have revealed the presence of sesquiterpenoids (Kaur and Kalsi, 1985;Kalsi et al, 1989;Goyal et al, 1990;Zhang et al, 2012) and we recently reported twentyfour sesquiterpene lactones isolated from I. racemosa . As part of our continuous interest in traditional Chinese herbal medicine, four trinorsesquiterpenoids (1-4) including two new trinorsesquiterpenoids 1 and 3 ( Fig.…”

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confidence: 98%

Trinorsesquiterpenoids from Inula racemosa

Zhao

Zhai³

et al. 2013

Phytochemistry Letters

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“…The characteristic components of the genus Inula are sesquiterpenes, such as eudesmanes, germacranes, guaianes, and bis-sesquiterpenes. In the previous reports, various sesquiterpenoids, triterpenoids, and lignans have been isolated and identified in the plant [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Isoalantolactone derived from I. racemosa roots exhibited repellency and insecticidal activity to rice weevil, Sitophilus oryzae and ovicidal activity against maize borer, Chilo partellus [20,21] However, a literature survey has shown that there is no report on larvicidal activity of I. racemosa roots against A. albopictus.…”

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Mosquito Larvicidal Constituents from the Ethanol Extract ofInula racemosaHook. f. Roots againstAedes albopictus

Liu

Sun

et al. 2014

Journal of Chemistry

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The aim of this research was to determine larvicidal activity of the ethanol extract ofInula racemosaHook. f. (Compositae) roots against the larvae of the Culicidae mosquitoAedes albopictusand to isolate any larvicidal constituents from the extract. Based on bioactivity-guided fractionation, 11,13-dihydroisoalantolactone (1), macrophyllilactone E (2), 5α-epoxyalantolactone (3), and epoxyisoalantolactone (4) were isolated and identified as the active constituents. Compounds1and2exhibited strong larvicidal activity against the early fourth-instar larvae ofA. albopictuswith LC50values of 21.86 μg/mL and 18.65 μg/mL, respectively, while the ethanol extract had a LC50value of 25.23 μg/mL. Compounds3and4also possessed larvicidal activity against the Asian tiger mosquitoes with LC50values of 29.37 μg/mL and 35.13 μg/mL, respectively. The results indicated that the ethanol extract ofI. racemosaand the four isolated constituents have potential for use in the control ofA. albopictuslarvae and could be useful in the search of newer, safer, and more effective natural compounds as larvicides.

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Three oxygenated alantolides from Inula racemosa

Cited by 30 publications

References 5 publications

Acidic isomerization of alantolactone derivatives

Acidic isomerization of alantolactone derivatives

Trinorsesquiterpenoids from Inula racemosa

Mosquito Larvicidal Constituents from the Ethanol Extract ofInula racemosaHook. f. Roots againstAedes albopictus

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