Phenolic compounds from aerial parts as chemosystematic markers in the Scorzonerinae (Asteraceae)

In continuation of our chemosystematic survey of the Lactuceae tribe of the Asteraceae family and of the Scorzonerinae subtribe in particular, we have studied the profiles of phenolic compounds of aerial parts of Geropogon glaber L., and seven representatives of each of the genera Scorzonera and Tragopogon. Employing HPLC-MS³, 56 phenolics amongst the seven phenolic acids and 49 flavonoids were characterized. All phenolic acids were assigned as caffeoyl quinic acid derivatives and 15 of the flavonoids were identified as aglyca and glycoside of apigenin, luteolin, and quercetin, whilst the remaining flavonoids were only partially characterized. Multivariate data analyses of the HPLC-DAD quantification data revealed no significant differences between the three genera Geropogon, Scorzonera, and Tragopogon. However, some clusters of chemically very similar species amongst them the group of Tragopogon minor Mill., Tragopogon orientalis L., and Tragopogon pratensis L. (also regarded as subspecies of T. pratensis by some authors) were identified. In contrast, the three taxa of Scorzonera hispanica s.l. (Scorzonera crispatula Boiss., S. hispanica L., and Scorzonera trachysperma Guss.) were chemically less similar and partially clustered with other morphologically less closely related species.     

Caffeic acid ester derivatives and flavonoids of genus Arnaldoa (Asteraceae,Barnadesioideae)

The phytochemical composition of Arnaldoa species is barely known. In this work, the occurrence of caffeic acid ester derivatives and flavonoids in A. argentea, A. macbrideana and A. weberbaueri was established by liquid chromatography associated to high-resolution mass spectrometry analyses and comparison with data from isolated compounds. The distribution of chlorogenic acids in the genus Arnaldoa is herein described for the first time. The metabolite profile of Arnaldoa species was compared to that of Tithonia diversifolia, a known and rich source of chlorogenic acids and sesquiterpene lactones. In addition to the mono- and dicaffeoyl quinic acids present in T. diversifolia, Arnaldoa species exhibited the mono- and dicaffeoyl tartaric acids. Furthermore, mass features correspondent to that of sesquiterpene lactones present in T. diversifolia were not observed in Arnaldoa species. The chemotaxonomic implications of caffeic acid ester derivatives and flavonoid glycosides, as well as the potential absence of sesquiterpene lactones in the genus Arnaldoa and subfamily Barnadesioideae are discussed.     

Chemotaxonomic value of flavonoids in Chromolaena congesta (Asteraceae)

The phytochemical investigation on the aerial parts of Chromolaena congesta led to the isolation of nine flavonoids, known in the literature as genkwanin (1) kumatakenin (2) acacetin (3), kaempferol 3-methyl ether (4), apigenin (5), apigenin 5,7-dimethyl ether (6), apigenin 5-methyl ether (7), luteolin (8) and kaempferol (9). The chemical structures were established on the basis of spectral evidence. All the compounds were isolated from this species for the first time. The results from the present study provide further information about the flavonoids as taxonomic marker of the genus Chromolaena, and the chemotaxonomic significance of these compounds were also summarized.     

Phenolics from Tanacetum sinaicum (Fresen.) Delile ex Bremer & Humphries (Asteraceae)

The phytochemical investigation on Tanacetum sinaicum (Fresen.) Delile ex Bremer & Humphries led to the isolation of eight flavonoid aglycones (apigenin 1, acacetin 2, luteolin 3, chrysoeriol 4, cirsilineol 5, jaceidin 6, chrysosplenetin 7 and vitexicarpin; casticin 8), four flavonoid glycosides (apigenin 7-O-β-glucopyranoside 9, apigenin 7-O-β-glucuronide 10, luteolin 7-O-β-glucopyranoside 11 and luteolin 7-O-β-glucuronide 12) and three phenolics (4-hydroxy-3-methoxy benzoic acid 13, 3,4-dimethoxy benzoic acid 14 and 4-hydroxy acetophenone 15). Their structures were determined by chemical and spectroscopic analysis. Among them, compounds 1–3, 9, 11, 13 and 14 were reported for the first time from T. sinaicum. The chemotaxonomic significance of the isolated flavonoids was also summarized.     

Current and future distributions of Espeletiinae (Asteraceae) in the Venezuelan Andes based on statistical downscaling of climatic variables and niche modelling

ABSTRACT

Background: Páramos are the high-elevation ecosystems of the humid tropical Andes, characterised by the presence of giant rosettes of the Espeletiinae subtribe (Asteraceae). Forecasted climate change is likely to reduce the extent of the area climatically suitable/occupied currently by Espeletiinae and their elevation distribution patterns.

Aims: The aim of this study was to estimate the potential impacts of forecasted climate change on the geographic distribution (extent of area and elevation distribution patterns) of 28 species of Espeletiinae that have been recorded in the Cordillera de Mérida, Venezuela.

Methods: Six bioclimatic variables, downscaled to a 90 m × 90 m cell size, were used to construct species distribution models (SDM) for the 28 species to model their current and likely future distribution (2070) by using two general circulation models and four representative concentration pathways (RCP).

Results: Nine species were estimated to have potential distribution over less than 1000 km² and five over less than 500 km², in current climatic conditions. Fifteen and eight species had elevation spans narrower than 1000 m and 500 m, respectively. No significant differences in modelled areas or spans were detected between north, central and south sections of the Cordillera de Mérida. Mean ± SE future reduction in the extent of area climatically suitable were estimated between 51.3% ± 6.3% (RCP2.6) and 78.1% ± 5.3% (RCP8.5), coupled with upward range retreat of between 277.8 m ± 27.4 m (RCP2.6) and 762.5 m ± 59.8 m (RCP8.5).

Conclusions: Our study predicts large reductions in modelled area and important upward shifts in the distribution of Venezuelan Espeletiinae by 2070 compared to their current distribution.     

Chemotaxonomic implications of the absence of sesquiterpene lactones in Grazielia multifida (DC.) R.M.King & H.Rob. (Asteraceae)

The phytochemical investigation of Grazielia multifida aerial parts yielded eight compounds, including four ent-kaurenic acid diterpenes derivatives, 15-tiglinoyloxy-ent-kaur-16-en-19-oic acid (1), 15-hydroxy-ent-kaur-16-en-19-oic acid (2), 17-hydroxy-ent-kaur-15-en-19-oic acid (3) and 15-isovaleroyloxy-ent-kaur-16-en-19-oic acid (4), one amino acid, tryptophan (5), and three flavonoids, eupafolin (6), guaijaverin (7) and quercitrin (8). The structures of the isolated compounds were established based on analysis of their spectroscopic data and comparison with literature. All the compounds were isolated from this species for the first time. The chemotaxonomic significance of the absence of sesquiterpene lactones in G. multifida has also been summarized.     

Vernoguinosterol and vernoguinoside, trypanocidal stigmastane derivatives from Vernonia guineensis (Asteraceae)

Two bitter stigmastane derivatives, vernoguinosterol (1) and vernoguinoside (2), have been isolated from the stem bark of Vernonia guineensis and their structures eludicated using spectroscopic methods. The new compounds exhibit trypanocidal activity.     

Stigmastane derivatives and isovaleryl sucrose esters from Vernonia guineensis (Asteraceae)

Vernoguinoside, 16beta,22R;21,23S-diepoxy-3beta-O-beta-D-glucopyranosyloxy-21S,24-dihydroxy-5alpha-stigmasta-8,14-dien-28-one (1), a new stigmastane derivative, 16beta,22R;21,23S-diepoxy-21S,24-dihydroxy-5alpha-stigmasta-8,14-diene-3,28-dione (2) and two new sucrose esters, 1',3,3',4',6'-pentakis-O-(3-methylbutanoyl)-beta-D-fructofuranosyl alpha-D-glucopyranoside (3) and 1',2,3',6,6'-pentakis-O-(3-methylbutanoyl)-beta-D-fructofuranosyl alpha-D-glucopyranoside (4), have been isolated from the stem bark of Vernonia guineensis. The structures of the new compounds were determined on the basis of spectroscopic evidence.     

Natural products from Tolpis barbata (L.) Gaertn. (Asteraceae,Cichorieae)

One sesquiterpene lactone – 9α-hydroxy-3-deoxyzaluzanin C, three benzopyrans: desmethoxyencecalin (6-acetyl-2,2-dimethylchromene), desacetylripariochromen B and 6-(1-hydroxyethyl)-2,2-dimethylchromene, one coumarin – scopoletin and two eugenol derivatives were isolated from the roots of Tolpis barbata (L.) Gaertn, hitherto unexamined species. In the extract from aerial parts of the plant, five known phenolic compounds, namely: esculin, esculetin, chlorogenic acid (5-CQA), luteolin 7-O-glucoside and 3,5-dicaffeoylquinic acid (3,5-DCQA) were identified as major constituents. Except for the two coumarins – scopoletin and esculetin, which were previously obtained from Tolpis webbii Sch.Bip. and T. proustii Pit., the isolated and identified compounds have not been previously reported as constituents of Tolpis spp. Though benzopyrans were found in numerous species of the Asteraceae, their occurrence in the tribe Cichorieae has not been demonstrated before.     

Growth rates, reproductive phenology, and pollination ecology of Espeletia grandiflora (Asteraceae), a giant Andean caulescent rosette

From March 2001 to December 2002, we studied the reproductive phenology, pollination ecology, and growth rates of Espeletia grandiflora Humb. and Bonpl. (Asteraceae), a giant caulescent rosette from the Páramos of the Eastern Andes of Colombia. Espeletia grandiflora was found to be predominantly allogamous and strongly self-incompatible. Bumblebees (Bombus rubicundus and B. funebris) were the major pollinators of E. grandiflora, although moths, hummingbirds, flies, and beetles also visited flowers. Inflorescence development began in March and continued through August to September. Plants flowered for 30 - 96 days with a peak from the beginning of October through November. The percentage of flowering plants strongly differed among size classes and between both years. Seed dispersal occurred as early as September through May of the following year. The average absolute growth rate for juveniles and adults rate was 7.6 cm/year. Given the scarcity of floral visitors at high altitudes due to climatic conditions, we suggest that even small contributions from a wide range of pollinators might be advantageous for pollination of E. grandiflora. Long-term studies on different populations of E. grandiflora are required to determine if the high growth rates are representative, to quantify the variation in the flowering behavior within and among populations, and to establish if nocturnal pollination is a trait that is exclusive to our population of E. grandiflora.     

Chemical constituents from Flourensia resinosa S.F. Blake (Asteraceae)

β-eudesmol (1), cryptomeridiol (2), ilicic acid (3), 5,7-dihydroxyflavone (chrysin, 4) and 7-O-methyl-chrysin (tectochrysin, 5) were isolated as the major constituents from the acetone extract of the aerial parts of Flourensia resinosa S.F. Blake (Asteraceae), along with flourensiadiol (6), spathulenol (7), p-acetophenol (8), lupeol (9), β-sitosterol (10), triacontanol (11) and squalene (12). Based on previous studies, this chemical composition for F. resinosa is in accordance with the chemical profile of other species of Flourensia. The profile of flavonoids, sesquiterpenes and benzofurans may have chemotaxonomic significance within this genus.     

Hieracium busambarense,a new species of the sect. Grovesiana (Asteraceae) from Sicily (Italy)

Hieracium busambarense (Asteraceae), a new species from calcareous-dolomite cliffs of Rocca Busambra (western Sicily, Italy) is described and illustrated here.     

Flavonoids and phenolic acids from the aerial parts of Alyssum alyssoides L. (Brassicaceae)

Two phenolic acids (1 and 2) and seven flavonoids (3–9) were isolated from the aerial parts of Alyssum alyssoides (Brassicaceae). All these compounds (1–9) were isolated from this particular species for the first time. Their structures were identified, on the basis of MS and NMR spectra as: p-hydroxy-benzoic acid (1), 3-methoxy-4-hydroxybenzoic acid (vanillic acid) (2), kaempferol 3-O-β-D-glucopyranoside (astragalin) (3), kaempferol 3-O-(6″-α-L-rhamnopyranosyl)-β-D-glucopyranoside (nicotiflorin) (4), quercetin 3-O-β-D-glucopyranoside (isoquercetin) (5), quercetin 3-O-β-D-galactopyranoside (hyperoside) (6), isorhamnetin 3-O-β-D-glucopyranoside (7), isorhamnetin 3-O-β-D-galactopyranoside (8) and isorhamnetin 3-O-(6″-α-L-rhamnopyranosyl)-β-D-glucopyranoside (narcissin) (9). The chemotaxonomic significance of these compounds was summarized.