Four new eudesmane-type and one new eremophilane-type sesquiterpenes from the whole plant of Carpesium abrotanoides L

The extract of the whole plant of Carpesium abrotanoides L. yielded five new sesquiterpenes including four eudesmanes (1-4) and one eremophilane (5). The new compounds were characterized by spectroscopic analysis especially 1D and 2D NMR spectroscopy and HRESIMS data. Structurally, both compounds 1 and 2 were sesquiterpene epoxides and 2 owned an epoxy group at C-4/C-15 position to form a spiro skeleton. Compounds 4 and 5 were two sesquiterpenes without lactones and 5 possessed a carboxy group in the molecule. Additionally, all the isolated compounds were preliminarily evaluated for the inhibitory activity against SARS-CoV-2 main protease. As a result, compound 2 showed moderate activity with an IC50 value of 18.79 μM, while other compounds were devoid of noticeable activity (IC50 > 50 μM).

Eudesmane-type sesquiterpene glycosides: sonneratiosides A-E and eudesmol β-D-glucopyranoside from the leaves of Sonneratia alba

Five eudesmane-type sesquiterpene glycosides, named sonneratiosides A-E (1-5), were isolated from the leaves of Sonneratia alba (Lythraceae). The aglycone of sonneratioside A was identified as cryptomeridiol also known as proximadiol. X-ray crystallographic analysis of sonneratioside A confirmed its structure and its absolute stereochemistry. Eudesmol β-D-glucopyranoside (6) was also isolated from nature for the first time. The tyrosinase inhibitory activity was assayed for the new compounds together with seven known compounds. Among them, arbutin (12) showed the expected activity and luteolin 7-O-rutinoside (10) showed comparable activity to arbutin.

Two New Eudesmane Sesquiterpenoids from the Flowers of Chrysanthemum indicum

The flowers of Chrysanthemum indicum, i.e. Ye-ju-hua recorded in the Chinese Pharmacopoeia, has been widely used in China as an important heat-clearing and detoxifying herb for the treatment of inflammation, headache, and vertigo. A phytochemical investigation of this herb has led to the isolation of two new eudesmane sesquiterpenoids, 7-epi-eudesm-4(15),11(13)-diene-1β,3β-diol (1) and 7-epi-1β-hydroxy-β-eudesmol (2). The molecular structures of these new sesquiterpenoids were established based on the comprehensive spectroscopic analyses, including NMR, MS, and IR, and comparing with the literatures.

Sesquiterpene glycosides from the roots of Codonopsis pilosula

Three new sesquiterpene glycosides, named codonopsesquilosides A−C (1−3), were isolated from an aqueous extract of the dried roots of Codonopsis pilosula. Their structures including absolute configurations were determined by spectroscopic and chemical methods. These glycosides are categorized as C₁₅ carotenoid (1), gymnomitrane (2), and eudesmane (3) types of sesquiterpenoids, respectively. Compound 1 is the first diglycoside of C₁₅ carotenoids to be reported. Compound 2 represents the second reported example of gymnomitrane-type sesquiterpenoids from higher plants. The absolute configurations were supported by comparison of the experimental circular dichroism (CD) spectra with the calculated electronic CD (ECD) spectra of 1−3, their aglycones, and model compounds based on quantum-mechanical time-dependent density functional theory. The influences of the glycosyls on the calculated ECD spectra of the glycosidic sesquiterpenoids, as well as some nomenclature and descriptive problems with gymnomitrane-type sesquiterpenoids are discussed.

Botryane, noreudesmane and abietane terpenoids from the ascomycete Hypoxylon rickii

In the course of our screening for new bioactive natural products, a culture of Hypoxylon rickii, a xylariaceous ascomycete collected from the Caribbean island Martinique, was identified as extraordinary prolific producer of secondary metabolites. Ten metabolites of terpenoid origin were isolated from submerged cultures of this species by preparative HPLC. Their structures were elucidated using spectral techniques including 2D NMR and HRESIMS. Three of the compounds were elucidated as new botryanes (1-3) along with three known ones, i.e. (3aS)-3a,5,5,8-tetramethyl-3,3a,4,5-tetrahydro-1H-cyclopenta[de]isochromen-1-one (4), (3aS,8R)-3a,5,5,8-tetramethyl-3,3a,4,5,7,8-hexahydro-1H-cyclopenta[de]isochromen-1-one (5) and botryenanol (6). Further three new sesquiterpenoids featured a 14-noreudesmane-type skeleton and were named hypoxylan A-C (7-9); the diterpenoid rickitin A (10) contains an abietane-type backbone. Compounds 1, 2, 3, 7, and 10 showed cytotoxic effects against murine cells.

Botryane, noreudesmane and abietane terpenoids from the ascomycete Hypoxylon rickii

In the course of our screening for new bioactive natural products, a culture of Hypoxylon rickii, a xylariaceous ascomycete collected from the Caribbean island Martinique, was identified as extraordinary prolific producer of secondary metabolites. Ten metabolites of terpenoid origin were isolated from submerged cultures of this species by preparative HPLC. Their structures were elucidated using spectral techniques including 2D NMR and HRESIMS. Three of the compounds were elucidated as new botryanes (1-3) along with three known ones, i.e. (3aS)-3a,5,5,8-tetramethyl-3,3a,4,5-tetrahydro-1H-cyclopenta[de]isochromen-1-one (4), (3aS,8R)-3a,5,5,8-tetramethyl-3,3a,4,5,7,8-hexahydro-1H-cyclopenta[de]isochromen-1-one (5) and botryenanol (6). Further three new sesquiterpenoids featured a 14-noreudesmane-type skeleton and were named hypoxylan A-C (7-9); the diterpenoid rickitin A (10) contains an abietane-type backbone. Compounds 1, 2, 3, 7, and 10 showed cytotoxic effects against murine cells.

Highly oxygenated sesquiterpenes in Artemisia alba Turra

Ten new sesquiterpene alcohols of which seven germacranes, a eudesmane, a guaiane and an oplopane were isolated from the aerial parts of Artemisia alba Turra. Their structures and relative stereochemistry were elucidated by spectral methods ((1)H and (13)C NMR, COSY, HSQC, HMBC, NOESY, and MS). In addition, the known 7-hydroxycadin-4-en-3-one, centaureidin and axillarin were found for the first time in the studied species.

Terpenoids from the roots of Drypetes hoaensis and their cytotoxic activities

Seven terpenoids consisting of five sesquiterpenoids, hoaensieremone, hoaensieremodione, hoaensifuranonal, hoaensieudesone, and hoaensibenzofuranal, and two friedelane triterpenoids, 3α-(E)-p-coumaroyloxyfriedelan-7-one and 3α-(E)-caffeoyloxyfriedelan-7-one were isolated from the dichloromethane extract of the roots of Drypetes hoaensis. Additionally, twelve known compounds and vanillin were isolated. Their structures were established on the basis of spectroscopic analysis, as well as by comparison with literature data. The anticancer activity of nine of these compounds was investigated.

Eudesmane-type sesquiterpene derivatives from Laggera alata

Ten eudesmane-type sesquiterpene derivatives (1-10), including six cuauhtemone derivatives (1-6), one di-norsesquiterpene (3-oxo-di-nor-eudesma-4-en-11-oic acid, 7), and three eudesmane glycosides (alatoside F-H, 8-10) were isolated from the whole plants of Laggera alata together with 12 known compounds. Their structures were elucidated on the basis of extensive spectroscopic analysis, acid hydrolysis, and compounds 1 and 7 were studied by single-crystal X-ray diffraction analysis. The absolute configuration of 1 was determined by the application of the modified Mosher's method. All of the isolated eudesmane-type sesquiterpenes were evaluated for their cytotoxic activities on six human cancer cell lines, but all of the compounds were inactive on the tested cell lines in the concentration of 100 μg/mL.

Bioactive eudesmane and germacrane derivatives from Inula wissmanniana Hand.-Mazz

Phytochemical investigation of Inula wissmanniana Hand.-Mazz. afforded 21 eudesmane and germacrane derivatives, including rare 4,5-secoeudesman-12,5-olide, eudesman-12,5-olide, 3,4-secoeudesman-12-oic acid, and germacra-4-en-12,6-olides. Their structures were elucidated by combinative analyses of MS, NMR, electronic circular dichroism, and X-ray crystallography data. Moreover, most of the isolates exhibited inhibition against lipopolysaccharide-induced nitric oxide production in RAW264.7 macrophages and cytotoxicity in HepG2, PC-3, and MGC-803 tumor cells.