New labdane diterpenoids from Sideritis chamaedryfolia

From the aerial parts of Sideritis chamaedryfolia six previously known ent-kaurene diterpenoids have been isolated. In addition, seven new labdane derivatives have also been obtained from the same source. The structures of these new natural diterpenoids have been established by chemical spectroscopic means and by correlation with known products.     

Galeuterone and pregaleuterone,labdane diterpenoids from Galeopsis reuteri

From the aerial part of Galeopsis reuteri a furanic labdane diterpenoid, galeuterone, and its prefuranic derivative, pregaleuterone, have been isolated. The structures of these substances have been established mainly by spectroscopic means.     

Characteristic lindenane sesquiterpenoid dimers and labdane diterpenoids from Chloranthus serratus

Chemical investigation on the roots of Chloranthus serratus (Chloranthaceae) afforded 11 terpenoids, including four lindenane-type sesquiterpenoid dimers (1–4), and seven labdane diterpenoids (5–11). The structures of these terpenoids were established by spectroscopic analysis (MS, ¹H, and ¹³C NMR). Compounds 4–11 were isolated from C. serratus for the first time. The chemotaxonomic significance of the isolated compounds was summarized herein.     

Highly Oxygenated Labdane Diterpenoids from Stevia rebaudiana and Their Anti-Atherosclerosis Activities

Five unknown labdane diterpenoids Stevelins A–E ( 1–5 ), three known labdane diterpenoids ( 6–8 ) and three labdane norditerpenoids ( 9–11 ) were isolated from the Stevia rebaudiana. The structures were determined primarily via NMR spectroscopic data and HR-ESI-MS experiments. X-ray crystallography using CuK_α radiation was used to determine the absolute configurations of 1 , and the absolute configurations of 2–5 were deduced by electronic circular dichroism (ECD) calculations. The potential anti-atherosclerosis activities of all compounds were evaluated by measuring their inhibitory effects on the macrophage foam cell formation. As a result, most isolated compounds could significantly inhibit oxidized low-density lipoprotein (ox-LDL)-induced macrophage foam cell formation, which suggests that these compounds may be promising candidates in the treatment for atherosclerosis.     

Sesquiterpene lactones from a texas population of Helianthus maximiliani

A population of Helianthus maximiliani from south-central Texas was shown to have a sesquiterpene lactone chemistry which was completely different from that reported for collections of this species from Kansas and north-central Texas. A series of five new guaianolides, two germacrolides (trans, trans-1(10),4(5)-germacradienolides), one of which is new, and a known labdane diterpene acid were isolated from a chloroform extract. Structures were determined by spectral and chemical methods. The structure of one guaianolide had been previously determined by X-ray crystallography.     

Structural Characterization and Biological Evaluation of 18‐Nor‐ent‐labdane Diterpenoids from Grazielia gaudichaudeana

The phytochemical investigation of Grazielia gaudichaudeana aerial parts yielded 15 compounds, including diterpenes, triterpenes, sterols and flavonoids. With exception to ent‐kaurenoic acid diterpenes, the compounds isolated are being described for the first time in this species. Some unusual ¹H‐NMR chemical shifts of 18‐nor‐ent‐labdane ( 7 – 9 ) led us carry out a conformational analysis by theoretical calculations in order to support the experimental data. Moreover, due to the limitation of studies focused on pharmacological potential of Grazielia gaudichaudeana, the present study was carried out to investigate the antioxidant, antiproliferative, antiviral, antileishmanial and antimicrobial activities from the extract, fractions and isolated compounds obtained from this species. Ethyl acetate fraction showed significant activity in the antiproliferative assay, with GI₅₀ range of 3.9 to 27.2 μg mL^?1. Dichloromethane fraction, rich in diterpenoids, inhibited all human tumor cell lines tested, and the nor‐labdane 7 showed potent cytotoxic activity against glioma and ovary cancer cell lines.     

Isolation and structural elucidation of two new labdane diterpenoids from the aerial part of Roylea cinerea

Two new labdane diterpenoids, cinereanoid A (1) and cinereanoid B (2), along with five known compounds, calyone (3), pilloin (4), 1-methylindole-3-carboxaldehyde (5), β-sitosterol (6) and stigmasterol (7) were isolated from the aerial parts of Roylea cinerea (Lamiaceae). The new structures were determined by using IR, MS, 1D, 2D NMR spectroscopy. The structure of both new compounds was further confirmed by single crystal X-ray crystallographic analysis. In this study we have also reported single crystal X-ray structure of compound 3 which unambiguously confirmed the relative stereochemistry of tertiary hydroxyl and methyl groups, as it was not established by earlier report. Compounds 4 and 5 were isolated for the first time from this plant. In view of very few reports about this species, this report has increased the phytochemical knowledge about R. cinerea.     

Labdane diterpenes from Brickellia vernicosa

The investigation of Brickellia vernicosa afforded, in addition to the known 3α-hydroxycativic acid, three new labdane derivatives. The structures and stereochemistry have been established by spectroscopic methods and chemical transformations.     

Neue labdan-derivate aus Gutierrezia-arten

The aerial parts of Gutierrezia lucida afforded three new diterpenic acids, all closely related to agathic acid and those of G. mandonii also three diterpenic acids, which again are labdane derivatives. The structures were elucidated by spectroscopic methods and some chemical transformations. The roots of these species and of a further one only contain triterpenes and no acetylenes. The chemotaxonomic situation is briefly discussed.     

Rare,seven-membered cyclic ether labdane diterpenoid from Dodonaea polyandra

Previous phytochemical studies on the leaf resin of dioecious plant species Dodonaea polyandra have identified the presence of furanoclerodane diterpenoids. As part of ongoing research on this species the chemical profile of an individual plant displaying male flowers was investigated. Repeated chromatographic separation of a resinous extract from the leaves of the plant yielded three labdane diterpenoids, 13,17-epoxy-13-methyl-15-oxo-labda-7-ene (1), 17-hydroxy-13-methyl-labda-7,13Z-diene-15-oic acid (2) and 13-methyl-17-oxo-labda-7,13Z-diene-15-oic acid (3) and a fourth known labdane diterpenoid (4) reported as being isolated from a natural source for the first time. Structural elucidation was carried out using conventional 1D and 2D NMR and mass spectrometry together with other complementary techniques (UV and IR). The leaf extract from this individual of D. polyandra with male flowers present displays a marked difference in the chemical composition of diterpenoids compared to previously studied extracts from the leaves of this species.     

Novel labdane diterpenoids from the aerial parts of Leonurus japonicus

Three new labdane diterpenoids, leojapones A–C (1–3), along with a new artifactual analogue (4) and four known terpenoids, were isolated from the EtOAc extract of the aerial parts of Leonurus japonicus Houtt. Their structures were elucidated by spectroscopic analyses and physicochemical evidences. The effects of new compounds against the abnormal increase in platelet aggregation induced by adenosine diphosphate were examined. But instead of inhibiting the abnormal platelet aggregation, compounds 1–3 boosted it significantly.     

Labdane derivatives from hemizonia species

The investigation of three Hemizonia species afforded in addition to known compounds seven new labdane derivatives, all derived from labd-13-en-15-ol. The absolute configuration of these diterpenes was determined by degradation of the triol by periodate cleavage, which afforded a known norditerpene ketone. From H. fitchii two new chromene esters and the cis-isomer of a known coumarate were isolated. H. congesta afforded in addition to labdane derivatives a hydroxycubebol.     

Neue labdan-derivate aus Carterothamnus anomalochaeta

The investigation of a Carterothamnus species afforded in addition to known euparine derivatives four new diterpenes, all being labdane derivatives. The structures are elucidated by ¹H-NMR-studies and by some chemical transformations. The chemotaxonomic situation is briefly discussed. The constituents of the Carterothamnus species show a distinct differentiation to those of the neighbouring groups; however, in addition they also indicate some relationships.     

Phytochemistry and chemotaxonomy of Sideritis species from the Mediterranean region

The phytochemical content of the Mediterranean species of the Sideritis genus has been reviewed. The components included in this review are monoterpenes, sesquiterpenes, diterpenes, triterpenes, sterols, flavones, coumarins and phenylpropanoids. From the chemotaxonomic point of view, we have divided the species from this region into four groups. The first of this is formed by taxa containing triterpenes, but not diterpenes. A second group is constituted by species having bicyclic diterpenes of the labdane type and not diterpenes. The third group is characterized by its content in tetracyclic diterpenes of the ent-kaurene type. A fourth group is composed of plants with tetracyclic diterpenes of the ent-beyer-15-ene and/or ent-atis-13-ene class. In addition, the relations of these Mediterranean species with those of the Macaronesian region have been examined.     

New labdane derivatives and further constituents of Brickellia species

The investigation of several Brickellia species and two further related species afford besides known compounds four new labdane derivatives, a new acetylenic carbinol and a new dihydrobenzofuran derivative. The structures have been elucidated by spectroscopic methods. The chemotaxonomic aspects are discussed briefly.     

Chemical variation in defensive secretions of four species of Nasutitermes

Nineteen monoterpenes and 13 diterpenes were distinguished in soldier defensive secretions of four species of Nasutitermes. Samples of N. columbicus, N. corniger, N. ephratae and N. nigriceps were collected in Costa Rica and Panama. Interspecifically, these species can be differentiated by monoterpenes, which exhibit a complex pattern. Intraspecifically, there is detectable variation in monoterpenes and diterpenes, each of which allows discrimination of four populations of N. corniger. Similarity between two Pacific populations of N. corniger from different environments, a tropical dry forest and a rainforest, suggests there is no climatic influence on chemical compositions of defensive secretions. In addition, results from Costa Rica provide evidence that the Atlantic population of N. corniger is derived from Pacific populations.     

Diterpenes and tetranorditerpenes from Acritopappus species

The investigation of four Acritopappus species afforded twenty-three new diterpenes of the labdane or kolavane type and three tetranorditerpenes as well as two new benzofuran derivatives and a hydroxybicyclogermacrene. The structures were elucidated by spectroscopic methods and by some chemical transformations. Though the absolute configuration were not established in all cases, most probably all diterpenes were ent-labdanes or kolavanes (clerodanes). The chemotaxonomic importance of this investigation is discussed briefly.     

Neue ent-atisiren- und ent-kaurensäure-derivate aus Helianthus-arten

The investigation of four Helianthus species afforded, in addition to known compounds, four new atisirenic acid derivatives, a new ent-kaurenic acid derivative, three new labdane derivatives and an unknown C₁₅-acetylenic compound. The structures of the diterpenes were elucidated by intensive NMR studies and some chemical transformations. An unusual fragmentation in the mass spectra of the atisirenes is discussed briefly.     

Morphological, chemical and genetic differentiation of two subspecies of Cistus creticus L. (C. creticus subsp. eriocephalus and C. creticus subsp. corsicus)

Cistus creticus L., an aromatic species from the Mediterranean area, contains various diterpenes bearing the labdane skeleton. The production of essential oil from this species has potential economic value, but so far, it has not been optimized. In order to contribute to a better knowledge of this species and to its differentiation, the morphological characters, volatile chemical composition and genetic data of two subspecies (C. creticus subsp. eriocephalus and C. creticus subsp. corsicus) were investigated. The leaf trichomes were studied using scanning electron microscopy. The chemical composition of Corsican essential oil (C. creticus subsp. corsicus) has been reported using GC, GC/MS and ¹³C NMR; the main constituents were oxygenated labdane diterpenes (33.9%) such as 13-epi-manoyl oxide (18.5%). Using plant material (54 samples) collected from 18 geographically distinct areas of the islands of Corsica and Sardinia, the basis of variation in the headspace solid-phase microextraction volatile fraction and an inter-simple sequence repeat genetic analysis were also examined. It was shown that the two subspecies of C. creticus differed in morphology, essential oil production, volatile fraction composition and genetic data.     

Diterpenoids from Teucrium scorodonia, three neo-clerodane derivatives

From the aerial parts of Teucrium scorodonia the previously known diterpenoid teupolin I and the flavone luteolin have been isolated. In addition, three new neo-clerodane derivatives have also been obtained from the same source. The structures of these new natural diterpenoids have been established by chemical and spectroscopic means and by correlation with known products.