Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Viola”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources
PubMed2006

Cycloviolacin H4, a hydrophobic cyclotide from Viola hederaceae.

Cycloviolacin H4, a new macrocyclic miniprotein comprising 30 amino acid residues, was isolated from the underground parts of the Australian native violet Viola hederaceae. Its sequence, cyclo-(CAESCVWIPCTVTALLGCSCSNNVCYNGIP), was determined by nanospray tandem mass spectrometry and quantitative amino acid analysis. A knotted disulfide arrangement, which was designated as a cyclic cystine knot motif and characteristic to all known cyclotides, is proposed for stabilizing the molecular structure and folding. The cyclotide is classified in the bracelet subfamily of cyclotides due to the absence of a cis-Pro peptide bond in the circular peptide backbone. A model of its three-dimensional structure was derived based on the template of the homologous cyclotide vhr1 (Trabi et al. Plant Cell 2004, 16, 2204-2216). Cycloviolacin H4 exhibits the most potent hemolytic activity in cyclotides reported so far, and this activity correlates with the size of a surface-exposed hydrophobic patch. This work has thus provided insight into the factors that modulate the cytotoxic properties of cyclotides.

Amino Acid Sequence↗
PubMed2006

A novel suite of cyclotides from Viola odorata: sequence variation and the implications for structure, function and stability.

Cyclotides are a fascinating family of plant-derived peptides characterized by their head-to-tail cyclized backbone and knotted arrangement of three disulfide bonds. This conserved structural architecture, termed the CCK (cyclic cystine knot), is responsible for their exceptional resistance to thermal, chemical and enzymatic degradation. Cyclotides have a variety of biological activities, but their insecticidal activities suggest that their primary function is in plant defence. In the present study, we determined the cyclotide content of the sweet violet Viola odorata, a member of the Violaceae family. We identified 30 cyclotides from the aerial parts and roots of this plant, 13 of which are novel sequences. The new sequences provide information about the natural diversity of cyclotides and the role of particular residues in defining structure and function. As many of the biological activities of cyclotides appear to be associated with membrane interactions, we used haemolytic activity as a marker of bioactivity for a selection of the new cyclotides. The new cyclotides were tested for their ability to resist proteolysis by a range of enzymes and, in common with other cyclotides, were completely resistant to trypsin, pepsin and thermolysin. The results show that while biological activity varies with the sequence, the proteolytic stability of the framework does not, and appears to be an inherent feature of the cyclotide framework. The structure of one of the new cyclotides, cycloviolacin O14, was determined and shown to contain the CCK motif. This study confirms that cyclotides may be regarded as a natural combinatorial template that displays a variety of peptide epitopes most likely targeted to a range of plant pests and pathogens.

Amino Acid Sequence↗
PubMed2003

Genetic effects of habitat fragmentation in Viola pubescens (Violaceae), a perennial herb with chasmogamous and cleistogamous flowers.

The reproductive biology of a plant species is important in the response of populations to habitat fragmentation, especially if plant-pollinator interactions are disrupted. The genetic effects of forest fragmentation were examined in the common understorey herb Viola pubescens, a species that produces self-pollinated cleistogamous (CL) flowers and potentially outcrossing chasmogamous (CH) flowers. Using allozymes, we measured genetic variation in different sized populations. These were located in woodlots of various sizes (0.5-40.5 ha) and distances from one another (0.3-46 km) within the agricultural landscape of central Ohio in the Midwestern United States. Changes in forest cover of each woodlot within the past 180 years were determined from historical sources and aerial photographs. Woodlot and population sizes were significantly and positively correlated with measures of genetic variation (A, P, HO and HE), with variation highest in populations in the largest woodlot population and lowest in the smallest woodlot population. Most large woodlots resulted from fluctuations in forest cover over the past 60 years, while smaller fragments remained the same size. Overall, populations in Crawford County were genetically differentiated from one another (theta = 0.34), but there was no relationship between genetic and geographical distance. Preliminary evidence for a single year indicated a high rate of outcrossing in most populations. Despite the CH/CL reproductive advantage and apparent outcrossing, populations of V. pubescens in small woodlots remain susceptible to potentially detrimental effects of fragmentation such as genetic drift and reduced levels of genetic variation.

Cluster Analysis↗
PubMed2005

Isolation and characterization of novel cyclotides from Viola hederaceae: solution structure and anti-HIV activity of vhl-1, a leaf-specific expressed cyclotide.

Based on a newly established sequencing strategy featured by its efficiency, simplicity, and easy manipulation, the sequences of four novel cyclotides (macrocyclic knotted proteins) isolated from an Australian plant Viola hederaceae were determined. The three-dimensional solution structure of V. hederaceae leaf cyclotide-1 (vhl-1), a leaf-specific expressed 31-residue cyclotide, has been determined using two-dimensional (1)H NMR spectroscopy. vhl-1 adopts a compact and well defined structure including a distorted triple-stranded beta-sheet, a short 3(10) helical segment and several turns. It is stabilized by three disulfide bonds, which, together with backbone segments, form a cyclic cystine knot motif. The three-disulfide bonds are almost completely buried into the protein core, and the six cysteines contribute only 3.8% to the molecular surface. A pH titration experiment revealed that the folding of vhl-1 shows little pH dependence and allowed the pK(a) of 3.0 for Glu(3) and approximately 5.0 for Glu(14) to be determined. Met(7) was found to be oxidized in the native form, consistent with the fact that its side chain protrudes into the solvent, occupying 7.5% of the molecular surface. vhl-1 shows anti-HIV activity with an EC(50) value of 0.87 microm.

Acquired Immunodeficiency Syndrome↗
PubMed2002

Allozyme diversity in natural populations of Viola palmensis Webb & Berth. (Violaceae) from La Palma (Canary Islands): implications for conservation genetics.

Genetic diversity was measured by allozyme electrophoresis in eight natural populations of the threatened Canarian endemic Viola palmensis Webb & Berth. (Violaceae). Nineteen alleles corresponding to 11 gene loci were detected. High levels of genetic diversity were found, ranging from 36.3 to 45.4 % for the percentage of polymorphic loci (P), from 1.45 to 1.60 for the average number of alleles per locus (A) and from 0.128 to 0.200 for the expected heterozygosity (H(e)). Between 85.5 and 96.6 % of genetic variability was apportioned within populations. As a whole, populations were not at Hardy-Weinberg equilibrium, with a deficit of heterozygous individuals attributable to the existence of genetic structuring in the populations analysed. The levels of interpopulation genetic differentiation were low (mean F(ST) = 0.100), while genetic identity pair-wise comparisons were high (mean I = 0.973) suggesting considerable levels of gene flow among populations. No relationship was detected between genetic differentiation and geographical distances between populations. An outcrossing insect-mediated breeding system might contribute to pollen dispersion of this species. For conservation genetics we suggest in situ preservation areas are defined that are free of disturbance and that include populations with the highest genetic diversity.

Alleles↗
PubMed2003

Variability of the essential oil of Viola etrusca.

Essential oils obtained from different populations of Viola etrusca from Italy have been analysed to verify the phenotypic discontinuity observed in a previous study. All of the essential oils contained methyl salicylate as a main constituent. However, multivariate analysis showed differences among some populations, in particular between northern and southern ones. Results suggest that this species could be undergoing a slow schizogenetic differentiation process due to its genetic isolation.

Cluster Analysis↗
PubMed2005

A glycosidic isoflavonoid from Viola hondoensis W. BECKER et H. BOISSIEU (Violaceae), and its effect on the expression of matrix metalloproteinase-1 caused by ultraviolet irradiation in cultured human skin fibroblasts.

Isolation of the ethyl acetate soluble fraction from aerial parts of Viola hondoensis W. BECKER et H. BOISSIEU yielded one major isoflavonoid glycoside, tectoridin-4'-O-beta-D-glucoside. The structure of the compound was certainly determined by chemical analyses, as well as 1D- and 2D-NMR spectroscopy. The compound exhibited potent inhibitory activity against the expression of matrix metalloproteinase-1 caused by UV-irradiation in cultured human skin fibroblasts.

Animals↗
PubMed2005

Isoflavonoid from Viola hondoensis, regulates the expression of matrix metalloproteinase-1 in human skin fibroblasts.

Long term and repeated exposure of ultraviolet (UV) light, a harmful environmental stress, on the skin often induces chronic skin diseases such as skin cancer as well as photoaging (premature skin aging), and the mechanisms of these skin damages are closely associated with up-regulation of matrix metalloproteinases (MMPs) activities. Here we investigated the effect of 2',4',7-trihydroxyisoflavone isolated from the whole plants of Viola hondoensis (Violaceae) on the expression of MMPs in UV-irradiated human skin fibroblasts in vitro. 2',4',7-Trihydroxyisoflavone markedly reduced UV-induced MMP-1 expression, but not MMP-2, at the both mRNA and protein levels in a dose-dependent manner. Our report is the first description for the ability of 2',4',7-trihydroxyisoflavone to regulate MMP-1 expression specifically.

Cells, Cultured↗
PubMed2003

Flavone C-glycosides from Viola yedoensis MAKINO.

A new flavone C-glycoside, apigenin 6-C-alpha-L-arabinopyranosyl-8-C-beta-L-arabinopyranoside, has been isolated from Viola yedoensis together with the known compounds, apigenin 6,8-di-C-alpha-L-arabinopyranoside, apigenin 6-C-alpha-L-arabinopyranosyl-8-C-beta-D-glucopyranoside (isoschaftoside), apigenin 6-C-beta-D-glucopyranosyl-8-C-alpha-L-arabinopyranoside (schaftoside), apigenin 6-C-beta-D-glucopyranosyl-8-C-beta-L-arabinopyranoside (neoschaftoside), apigenin 6,8-di-C-beta-D-glucopyranoside (vicenin-2), apigenin 6-C-alpha-L-arabinopyranosyl-8-C-beta-D-xylopyranoside, apigenin 6-C-beta-D-xylopyranosyl-8-C-alpha-L-arabinopyranoside, luteolin 6-C-beta-D-glucopyranoside (isoorientin) and luteolin 6-C-alpha-L-arabinopyranosyl-8-C-beta-D-glucopyranoside (isocarlinoside). The structures were determined by spectroscopic methods and new or revised (1)H- and (13)C-NMR spectral assignments are proposed for some compounds.

Flavonoids↗
PubMed1997

[Herbological study of some medicinal plants from Viola].

By herbological study, medicinal plants from Viola used as drugs are first recorded in the book "52 Diseased Preparation". The plants used as drugs in the ancient mainly are V. yedoensis, V. invospicus, V. diffusa, V. verecunda, V. davidii, V. moupinensis and V. patrinii.

Drugs, Chinese Herbal↗
PubMed2003

The cumulation of Wild pansy (Viola tricolor L.) accessions: the possibility of species preservation and usage in medicine.

Wild pansy (Viola tricolor L.) has a history in folk medicine of helping respiratory problems such as bronchitis, asthma, and cold symptoms. The drugs and extracts are prepared from raw material of pansy; it is a component of some prepared antitussives, cholagogues, dermatological medicines, roborants and tonics, alternatives, and anti-phlebitis remedies. Wild pansy is indigenous to or naturalized in large parts of Europe and the Middle East as far as Central Asia, also found through the United States. In the Lithuanian flora wild pansy habitats areas have been fast reducing; this not only limits the availability of the reserves of medicinal raw materials for pharmacy and therapy needs but also causes a menace to survival of species. The reasons of reduction of natural habitats and areas of wild pansy are not only unfavorable meteorological conditions (including summer droughts) but also the competition of different herbs and irrational human activities. The opportunities of preservation of the species wild pansy need to be cultivated and the most exhaustive adaptation research should be performed.

Ascorbic Acid↗
PubMed2005

Natural infection of Viola cornuta (Violaceae) with Cucumber mosaic virus, subgroup I.

Plants of Viola cornuta displaying typical virus symptoms were observed during spring 2003 in a plant nursery in Córdoba, central Argentina. Electron microscopic examinations of symptomatic leaf samples revealed the presence of isometric virus-like particles about 30 nm in diameter. Subsequent serological analysis allowed the identification of the pathogen as a subgroup I strain of Cucumber mosaic virus (CMV). These results were confirmed by antigen capture--reverse transcription--polymerase chain reaction with specific CMV primers, and digestion with a restriction enzyme. This is the first report of CMV infecting V. cornuta in Argentina.

Communicable Diseases↗
PubMed1984

In vivo EMG biofeedback in violin and viola pedagogy.

In vivo EMG biofeedback was found to be an effective pedagogical tool for removing unwanted left-hand tension in nine violin and viola players. Improvement occurred rapidly and persisted throughout a 5-month follow-up period. Further studies will be necessary to assess the effect of biofeedback independent of placebo effects. The brevity of the method and the magnitude of improvement warrant further investigation.

Adult↗
PubMed1988

Isolation, purification and partial characterization of an active anti-HIV compound from the Chinese medicinal herb viola yedoensis.

The dimethylsulfoxide extract of the Chinese medicinal herb Viola yedoensis demonstrates high inhibitory activity toward HIV-1 in vitro. The corresponding methanol extract also showed inhibitory activity but not as high as the dimethylsulfoxide extract. Anti-HIV activity in the extracts is accompanied by cytotoxicity, and we describe here the separation of the cytotoxic material from the active fraction. We also describe the procedure for isolation, purification, and separation of the active component from crude extracts of V. yedoensis as well as details of its activity against HIV-1. The UV-visible, infrared (IR) and proton nuclear magnetic resonance (NMR) data and certain other characteristics of the active compound are also presented. Initial chemical tests and the proton NMR and IR spectra indicate a high molecular weight sulphonated carbohydrate polymer, and chromatographic evidence suggests an MW between 10,000 and 15,000.

Antiviral Agents↗
PubMed1999

Pollen aperture heteromorphism. Variation in pollen-type proportions along altitudinal transects in Viola calcarata.

Some species produce pollen grains with different aperture numbers within a single individual (pollen aperture heteromorphism). In the pansy Viola diversifolia, aperture number is positively correlated with pollen germination speed, and negatively correlated with viability. In V. calcarata, young five-aperturate pollen grains germinate faster than four-aperturate ones. Heteromorphism could thus be favoured when pollination is unpredictable, as plants produce both very competitive and long-lived pollen grains. Depending on the efficiency of the pollinators, different proportions of pollen types will be optimal. In insect-pollinated species, such as V. calcarata, pollination efficiency generally decreases as elevation increases. We therefore expect a decrease in mean aperture number as altitude increases. This was found in four transects (out of six). Pollinator activity therefore has a potential impact on pollen morphology.

Plant Physiological Phenomena↗
PubMed1998

Violarvensin, a new flavone di-C-glycoside from Viola arvensis.

A new flavonoid di-C-glycoside, violarvensin (1), was isolated from the aerial parts of Viola arvensis, together with the known derivative violanthin (2). The structure of 1 was established as apigenin-6-C-beta-D-glucopyranosyl-8-C-beta-D-6-deoxygulopyrano side by spectral analysis.

Acetylation↗
PubMed1999

Seven novel macrocyclic polypeptides from Viola arvensis.

Seven novel macrocyclic polypeptides, designated as varv peptides B-H, have been isolated from the aerial parts of Viola arvensis. Their primary structures have been elucidated by automated Edman degradation and mass spectrometry. They all consist of 29 or 30 amino acid residues, covalently cyclized via the amide backbone and by three internal disulfide bridges. Their amino acid sequences are as follows: varv peptide B, cyclo-(TCFGGTCNTPGCSCDPWPMCSRNGLPVCGE); varv peptide C, cyclo-(TCVGGTCNTPGCSCSWPVCTRNGVPICGE); varv peptide D, cyclo-(TCVGGSCNTPGCSCSWPVCTRNGLPICGE); varv peptide E, cyclo-(TCVGGTCNTPGCSCSWPVCTRNGLPICGE); varv peptide F, cyclo-(TCTLGTCYTAGCSCSWPVCTRNGVPICGE); varv peptide G, cyclo-(TCFGGTCNTPGCSCDPWPVCSRNGVPVCGE); and varv peptide H, cyclo-(TCFGGTCNTPGCSCETWPVCSRNGLPVCGE). The varv peptides B-H exhibited high degrees of homology with the hitherto known macrocyclic peptides varv peptide A, kalata B1, violapeptide I, circulins A and B, and cyclopsychotride A.

Amino Acid Sequence↗