Systematic study of the Altissimae and Giganteae species groups of the genus Vernonia (Compositae)

Morphological variation within and between the taxa of the Altissimae (Vernonia altissima, V. ovalifolia, andV. flaccidifolia) and Giganteae (V. gigantea) was investigated. The data for these studies were obtained from population samples, herbarium specimens, and greenhouse-grown transplants. The taxa were hybridized in all possible combinations, and F₂ progeny were produced fromV. altissima XV. ovalifolia F₂’s. Fertility in the hybrids was estimated by examination of chromosome pairing at meiosis and by pollen stainability. It is concluded thatVernonia altissima should be regarded as a synonym ofV. gigantea and thatV. ovalifolia should be reduced to subspecific rank asV. gigantea ssp.ovalifolia. The evolution of the two subspecies ofV. gigantea is discussed.Vernonia flaccidifolia is maintained at the species level.     

A biosystematic study of the Interiores species group of the genus Vernonia (Compositae)

The taxa of the Interiores species group are treated as two species, one of which is divided into two subspecies.Vernonia missurica, a widespread taxon, has large flower heads (32-58 flowers per head), obtuse involucral bract tips, and a characteristic flavonoid Chromatographic profile.Vernonia baldwinii ssp.baldwinii, occurring throughout the Ozarks and Ouachitas, andV. baldwinii ssp.interior of the Central Plains possess smaller flower heads (17-34 flowers per head), acute or acuminate involucral bracts, and a different Chromatographic profile.Vernonia baldwinii ssp.baldwinii is distinguished from ssp.interior by the recurved involucral bract tips and by the possession of more flowers per head. Morphological data reveal that an intergradation zone exists between the population systems of the two subspecies along the edges of the Ozarks and Ouachitas. Although much gene exchange occurs between these two taxa, they maintain a level of genetic integrity that permits their ready recognition throughout wide ranges. All three taxa have a gametic chromosome number ofn = 17 and hybridize extensively with sympatric species.     

Glaucolide from Vernonia staehelinoides

Vernonia staehelinoides afforded a new glaucolide.     

Sesquiterpene lactones from Vernonia scorpioides and their in vitro cytotoxicity

Fresh leaves of Vernonia scorpioides are widely used in Brazil to treat a variety of skin disorders. Previous in vivo studies with extracts of this species had also demonstrated a high antitumor potential. This paper reports isolation of four sesquiterpene lactones (hirsutinolides and glaucolides), together with diacetylpiptocarphol, 8-acetyl-13-etoxypiptocarphol, luteolin, apigenin, and ethyl caffeate from fresh leaves and flowers of Vernonia scorpioides. The hypothesis that hirsutinolide 3 is formed during extraction was verified theoretically using Density Functional Theory. The effects of isolated compounds on in vitro tumor cells were investigated, as well as their genotoxicity by means of an in vitro comet assay. The results indicate that glaucolide 2 and hirsutinolide 4 are toxic to HeLa cells. These compounds were genotoxic in vitro, a property that appears to be related to the presence of their epoxy groups, which has been a more reliable indication of toxicity than substitution on C-13 or the presence of α,β-unsaturated keto-groups. These results need to be replicated in vivo in order to ascertain their toxicity.     

Insect antifeedant elemanolide lactones from Vernonia amygdalina

Chemical investigation of insect antifeedants from the bitter tasting leaves of Vernonia amygdalina by the application of semi-preparative reversed     

Glaucolides from Vernonia fulta

Four sesquiterpene lactones were isolated from the aerial parts of Vernonia fulta. Spectral characterization showed that three were new and one was known (i.e. glaucolide-B). The biogenetic relationship among these sesquiterpene lactones is discussed briefly.     

Further glaucolides from south african Vernonia species

The investigation of three South African Vernonia species afforded minute amounts of five new glaucolides, two monoepoxides and three diepoxides. The structures were elucidated by ¹H NMR spectroscopy. The roots of Vernonia sutherlandii contain, in addition to vernonataloide, bergamotene and santalene, minute amounts of the corresponding acetoxy derivatives.     

Isolation of a natural sterol and an aliphatic acid from Vernonia cinerea

From the roots of Vernonia cinerea a new natural sterol and a new aliphatic acid characterized as stigmast-5,17(20)-dien-3β-ol and 26-methylheptacosanoic acid, respectively, have been isolated together with stigmasterol and sitosterol.     

Poskeanolide,a seco-germacranolide and other sesquiterpene lactones from Vernonia species

The aerial parts of Vernonia cinerea, collected in Costa Rica, gave four new hirsutinolides while a sample from Malawi afforded glaucolide E and two related lactones. From V. poskeana a seco-germacranolide biogenetically closely related to a new glaucolide was isolated. The investigation of two Critoniopsis species gave in addition to known lactones a further glaucolide and a vernopatensolide. A related species, V. flexipappa, only gave glaucolide B. The structures were elucidated by highfield NMR spectroscopy.     

Two new species of Vernonia (Asteraceae: Vernonieae) from Panama

Two new species,Vernonia cocleana andV. chiriquiensis, are described from Panama. These endemic species are distinct from those in Central America and most closely resemble taxa in the West Indies and Argentina, respectively. These taxa are described and illustrated; a key is provided to the Panamanian species ofVernonia.     

Hirsutinolides and other sesquiterpene lactones from Vernonia species

The investigation of Vernonia compactiflora afforded in addition to known compounds a hirsutinolide and a glaucolide; the latter is most probably the direct precursor of the former. The aerial parts of V. monocephala contain the same hirsutinolide as well as the corresponding acetate, while those of V. chalybaea afforded glaucolide B. A reinvestigation of the aerial parts of V. cotoneaster gave in addition to the allenic lactone isolated before two further known ones as well as a new glaucolide. The structures of the lactones were elucidated by spectroscopic methods and some chemical transformations. The erroneously assigned stereochemistry at C-10 in the hirsutinolides has been revised. The biogenetic relationship of the Vernonia lactones is discussed briefly.     

Sesquiterpene lactones from two newly-described species of Vernonia: V. jonesii and V. pooleae

Two novel, non-glaucofide, germacrolide sesquiterpene lactones, 8α-methacryloyloxycostunolide-1(10),4(5)-diepoxide and 1-oxo-10α-OH-8α-methacryloyloxycostunolide (not fully characterized), were isolated from Vernonia jonesii and the previously described glaucolide B was identified from V. pooleae. This is one of the few reports of non-glaucolide type germacrolides in a New World species of Vernonia, although members of this class of sesquiterpene lactones are common constituents of Old World species of the genus. The chemical evidence supports the suggestion that V. jonesii may be part of a relictual, isolated group of the New World Vernonia, closely related to some of the Old World taxa.     

Seven new vernocuminosides from the stem bark of Vernonia cumingiana Benth

Seven new stigmastane-type steroidal glycosides, vernocuminosides H-N, have been isolated from the stem bark of Vernonia cumingiana Benth. The structures of these compounds were determined by NMR spectrometric methods including HSQC, HMBC, ¹H-¹H COSY, and NOE, as well as circular dichroism experiments. Anti-inflammatory activities of vernocuminosides I and K-N were determined.     

A revision of Vernonia series Buddleiifoliae (Compositae: Vernonieae)

SeriesBuddleiifoliae of the genusVernonia of southeastern South America consists of 18 species which are keyed, described, discussed and mapped.Vernonia goiasensis is proposed as a new name, whileV. wasshausenii andV. monocephala subsp.irwinii are described as new taxa, and V.asteriflora subsp.kuntzei is presented as a new combination.     

Vernonia georgiana—Species or hybrid?

Vernonia georgiana Bartlett was demonstrated to be of hybrid origin by means of hybridization experiments and comparisons of the artificial F₁ hybrids with herbarium specimens ofV. georgiana. The two parental species areV. angustifolia Michx. andV. acaulis (Walt.) Gleason.     

Chromosome numbers of dominican compositae

Chromosome numbers of 34 species of Dominican Compositae in 26 genera and nine tribes are reported. First counts are given forCoreopsis buchii (2n = 64),Lagascea mollis (2n = 34),Spilanthes urens (n = 16),Liabum subacaule (n = 18),Eupatorium sciatraphes (2n = 40),Hieracium gronovii (2n = 18),Vernonia buxifolia (2n = 34),V. sprengeliana (2n = 34),V. racemosa (2n = 28), andChaptalia leiocarpa (2n = 48,ca. 58). Our report forNarvalina domingensis (2n = 120) is the first for any species of this genus.     

Sesquiterpene lactones from Vernonia marginata

A reinvestigation of the polar fraction from Vernonia marginata afforded in addition to marginatin 13 new lactones, including six glaucolides, four closely related lactones with a new carbon skeleton, named vernomargolides, two jalcaguaianolides and a pseudoelephantopide, as well as a methyl ester probably derived from a glaucolide. The structures were elucidated by NMR spectroscopy and the stereochemistry was established by NOE difference spectroscopy. Possible biogenetic relationships are discussed briefly.     

A New species of Vernonia (Compositae) from Ecuador

Vernonia giannasii, a new species from Ecuador, is described and illustrated.