Violet Pigment Research Articles

Antimycobacterial activity in vitro of pigments isolated from Antarctic bacteria

In this study, we describe the antimycobacterial activity of two pigments, violacein, a purple violet pigment from Janthinobacterium sp. Ant5-2 (J-PVP), and flexirubin, a yellow-orange pigment from Flavobacterium sp. Ant342 (F-YOP). These pigments were isolated from bacterial strains found in the land-locked freshwater lakes of Schirmacher Oasis, East Antarctica. The minimum inhibitory concentrations (MICs) of these pigments for avirulent and virulent mycobacteria were determined by the microplate Alamar Blue Assay (MABA) and Nitrate Reductase Assay (NRA). Results indicated that the MICs of J-PVP and F-YOP were 8.6 and 3.6 μg/ml for avirulent Mycobacterium smegmatis mc²155; 5 and 2.6 μg/ml for avirulent Mycobacterium tuberculosis mc²6230; and 34.4 and 10.8 μg/ml for virulent M. tuberculosis H₃₇Rv, respectively. J-PVP exhibited a ~15 times lower MIC for Mycobacterium sp. than previously reported for violacein pigment from Chromobacterium violaceum, while the antimycobacterial effect of F-YOP remains undocumented. Our results indicate these pigments isolated from Antarctic bacteria might be valuable lead compounds for new antimycobacterial drugs used for chemotherapy of tuberculosis.

Photo-stability of Mixture of Violet Pigments Phycoerythrin and Phycocyanin Extracted without Separation from Discolored Nori Seaweed

Water-soluble pigment mixture was extracted from discolored nori seaweed without separating phycoerythrin (PE) and phycocyanin (PC). The stability of this mixture against light irradiation was studied for application as a violet food coloring additive. The PC component showed greater photo-stability than the PE component of the pigment solution (pH 7.0, 20°C) under irradiation at 5,300 and 7,800 Lx. The ratio of the second-order rate constant kPE/kPC which reflects photo-destruction was 9.3 (5,300 Lx) and 7.0 (7,800 Lx). The results were similar to those of a respective pigment separated by gel-chromatography. As for tonal changes, the a* value was decreased and both the b* and L* values were increased with progressing photo-destruction, namely, the violet color changed to pale dark-violet due to de-coloration of the red PE component. A reduction in photo-fading of 6.6% (PE) and 6.9% (PC) was achieved by 7,800 Lx irradiation for 5 h, compared with the control, by adding γ-cyclodextrin to the mixture.

Jahn−Teller Distorted Frameworks and Magnetic Order in the Rb−Mn−P−O System

Two previously uncharacterized members of the Rb-Mn-P-O system, RbMnP(2)O(7) and beta-RbMnHP(3)O(10), have been synthesized using a phosphoric acid flux synthetic route and their crystal and magnetic structures determined using neutron powder diffraction. The crystal structure of RbMnP(2)O(7) (space group P2(1)/c, a = 7.3673(2) A, b = 9.6783(2) A, c = 8.6467(2) A, and beta = 105.487(1) degrees) was found to be isostructural with RbFeP(2)O(7). The polymorph beta-RbMnHP(3)O(10) was also isolated as a single phase and found to crystallize in the space group C2 (a = 12.2066(5) A, b = 8.5243(3) A, c = 8.8530(4) A, beta = 107.233(2) degrees). Both structures consist of frameworks of corner-sharing MnO(6) octahedra linked together by condensed phosphate anions, with Rb(+) cations located in the intersecting channels. In both cases the Mn(3+) octahedra exhibit unusual Jahn-Teller distortions indicative of a plasticity effect driven by the steric requirements of the condensed phosphate anions, and this causes a strong violet coloration similar to that observed in the manganese violet pigment; the structure of this has yet to be determined. Magnetic susceptibility measurements show that both RbMnP(2)O(7) (T(N) = 20 K) and beta-RbMnHP(3)O(10) (T(N) = 10 K) undergo a phase transition at low temperatures to an antiferromagnetically ordered state. Low-temperature neutron powder diffraction studies show that the magnetic ground states of each of these materials involve both ferromagnetic and antiferromagnetic super-superexchange interactions between orbitally ordered Mn(3+), which are mediated by PO(4) tetrahedra. These interactions are compared and discussed.

Evolutionary replacement of UV vision by violet vision in fish

The vertebrate ancestor possessed ultraviolet (UV) vision and many species have retained it during evolution. Many other species switched to violet vision and, then again, some avian species switched back to UV vision. These UV and violet vision are mediated by short wavelength-sensitive (SWS1) pigments that absorb light maximally (lambda(max)) at approximately 360 and 390-440 nm, respectively. It is not well understood why and how these functional changes have occurred. Here, we cloned the pigment of scabbardfish (Lepidopus fitchi) with a lambda(max) of 423 nm, an example of violet-sensitive SWS1 pigment in fish. Mutagenesis experiments and quantum mechanical/molecular mechanical (QM/MM) computations show that the violet-sensitivity was achieved by the deletion of Phe-86 that converted the unprotonated Schiff base-linked 11-cis-retinal to a protonated form. The finding of a violet-sensitive SWS1 pigment in scabbardfish suggests that many other fish also have orthologous violet pigments. The isolation and comparison of such violet and UV pigments in fish living in different ecological habitats will open an unprecedented opportunity to elucidate not only the molecular basis of phenotypic adaptations, but also the genetics of UV and violet vision.

First Report of Pitch Canker on Pines Caused by Fusarium circinatum in Portugal.

In November of 2007, dieback symptoms (basal needle dieback, wilting, and dieback of terminal shoot) were observed on plant groups of Pinus radiata and P. pinaster in a tree nursery located in Anadia in the central region of Portugal (40°26'N, 08°23'W). Two containers with a total of 112 plants per pine species (with and without symptoms) were collected. Small pieces (5 mm long; two from the roots, stem at the soil level, and the aerial part, totaling six pieces) of 20 symptomatic plants were sterilized with 3% sodium hypochlorite, and isolations were performed on potato dextrose agar (PDA) supplemented with 0.5 mg/ml of streptomycin sulfate. A species of Fusarium was isolated from all infected tissues and pure cultures were obtained by single hyphal tip transfers on PDA and Spezieller Nährstoffarmer agar and incubated at 25°C for 10 days with a 12-h photoperiod. The species was identified as Fusarium circinatum Nirenberg & O'Donnell (= F. subglutinans Wollenweb & Reinking) on the basis of morphological and cultural characteristics (2). They produced white, aerial mycelia, violet pigment, typically three-septate macroconidia with slightly curved walls, single-celled microconidia, and characteristic sterile, coiled hyphae. Microconidia were ovoid or allantoid and born in false heads on aerial polyphialides. The identification was confirmed by PCR with specific primers CIRC1A/CIRC4A, resulting in a 360-bp DNA fragment of the two nuclear ribosomal intergenic spacer regions (3). Pathogenicity tests were performed by inoculating 5- and 9-month-old P. pinaster and P. radiata seedlings, respectively. Plants belonging to P. pinea species (8-month-old), the second most important pine in the country, were also included in the tests. Small strips of bark (10 × 1 mm) were cut from the stems and similar-sized pieces of PDA colonized by two isolates of F. circinatum were placed in contact with the open wounds and covered with Parafilm. Ten seedlings for each pine species, isolate, and control (with sterile PDA) were provided in a total of 90 plants. First symptoms, basal needle and shoot dieback, were observed in P. radiata 8 days after inoculation. One month later, all P. radiata and 70% of the P. pinaster plants were dead. In all P. pinea plants, needles turned red along the main stem, from center to periphery, but only 2% of these plants presented wilting of the terminal shoot after 1 month. No symptoms were observed on control seedlings. F. circinatum was reisolated from symptomatic plants of the three species tested. To our knowledge, this is the first report of F. circinatum in Portugal. Pitch canker, caused by Gibberella circinata (anamorph F. circinatum), is one of the most aggressive pathogens on several pine species in the world (1). In 2005, the fungus was detected in the European continent affecting P. radiata and P. pinaster in northern Spain.

The presence of trapped carbon dioxide in lapis lazuli and its potential use in geo-sourcing natural ultramarine pigment

Abstract The source of the previously unassigned weak band at 2340 cm −1 that is occasionally observed in the infrared spectrum of natural lapis lazuli pigment is here attributed conclusively to CO 2 trapped in the β-cage of lazurite. In addition, the geo-sourcing potential of this infrared feature for lapis lazuli is tested and found to be more ambiguous than previously suggested. The CO 2 absorption band is in fact observed in lapis lazuli samples from numerous disparate geographic locales including Afghanistan, Canada, Myanmar, Siberia, Tajikistan, and the Ural Mountains, as well as mineral hauyne samples from Germany and Italy. The spectral feature was absent from lapis lazuli samples from California, Chile, Colorado, and New York. Furthermore, poor quality lapis lazuli samples, regardless of locale, highly processed natural pigment samples, and all samples of synthetic ultramarine blue, green, and violet pigments were devoid of encapsulated CO 2 .

Violacein Extracted from Chromobacterium violaceum Inhibits Plasmodium Growth In Vitro and In Vivo

Violacein is a violet pigment extracted from the gram-negative bacterium Chromobacterium violaceum. It presents bactericidal, tumoricidal, trypanocidal, and antileishmanial activities. We show that micromolar concentrations efficiently killed chloroquine-sensitive and -resistant Plasmodium falciparum strains in vitro; inhibited parasitemia in vivo, even after parasite establishment; and protected Plasmodium chabaudi chabaudi-infected mice from a lethal challenge.

Production of violet pigment by a newly isolated psychrotrophic bacterium from a glacier in Xinjiang, China

A psychrotrophic XT1 strain (CGMCC 1194) isolated from a glacier in China's Xinjiang province produced violet pigments at a high content. This strain was identified as Janthinobacterium lividum XT1 by API kit and 16S rDNA analysis. The main fraction of violet pigment was violacein based on the analysis by HPLC-MS and 1 H NMR. The pigment production by J. lividum XT1 was not associated with the cell growth, and a cultivation temperature lower than 20 °C was required for the cell growth and pigment production. Sucrose was the most suitable carbon source, and casein was the best nitrogen source for cell growth and pigment formation. Mineral components in the medium, including CaNO 3 , FeSO 4 , riboflavin, MgSO 4 and nicotinic acid, showed different effects on the cell growth and pigment production. The maximum pigment productivity reached 0.8 g pigment per dry cell weight. The pigment production pattern by our isolate was different from that by other strains such as J. lividum reported so far.

First Report of Pitch Canker Caused by Fusarium circinatum on Pinus halepensis and P. pinea in Apulia (Southern Italy)

Since 2005, pitch canker symptoms have been observed in Apulia (southern Italy, 41°27'42.84″N, 15°33'0.36″E) on numerous trees of Pinus halepensis and P. pinea in urban parks and gardens. Trees showed crown decline as a consequence of dieback of twigs and branches and withering of needles. Bleeding cankers with abundant resin were visible on twigs and branches. The needles of affected twigs and branches wilted, faded, turned yellow, then red, and were discarded. Isolations from symptomatic needles, twigs, and branches were performed on water agar, potato dextrose agar (PDA), and pentachloronitrobenzene medium. A species of Fusarium was consistently isolated from all infected tissues, and pure cultures were obtained by single hyphal tip transfers on PDA and synthetic nutrient agar medium (2). Colonies were incubated at 22 ± 3°C for 7 to 10 days. They produced white aerial mycelia, violet pigment, typically 3-septate macroconidia with slightly curved walls, single-celled microconidia, and characteristic sterile hyphal coils. Microconidia were ovoid or allantoid and born in false heads on aerial polyphialides. The species was identified as Fusarium circinatum Nirenberg & O'Donnell (= F. subglutinans Wollenweb & Reinking) on the basis of morphological and cultural characteristics (3). The identification was confirmed by PCR with specific primers CIRC1A/CIRC4A. The specific primer pair amplified a 360-bp DNA fragment of the two nuclear ribosomal IGS region (4). The pathogenicity of three Italian isolates of F. circinatum from Pinus spp. (Fc1640, Fc1642, and Fc1643 stored in the collection of Dipartimento Scienze Agroambientali, Chimica and Difesa Vegetale, University of Foggia) was evaluated by artificial inoculations on 2-year-old potted seedlings of P. halepensis, P. pinea, P. nigra, P. sylvestris, P. domestica, P. pinaster, P. excelsa, P. radiate, and Pseudotsuga menziesii (10 seedlings for each species and fungal isolate). Small PDA plugs from actively growing colonies of F. circinatum were introduced into a U-shaped cut on the stem of the seedlings and wrapped with moist sterile cottonwool. An equal number of control plants of each Pinus spp. was inoculated with sterile agar. All plants were grown in a nursery at ambient temperature (20 to 28°C). Within 30 days after inoculation, resinous cankers appeared on the stem of the seedlings of P. halepensis, P. pinea, P. domestica, P. pinaster, and P. radiata. Basal needles began to wilt, turn yellow, then red, and were discarded. F. circinatum was reisolated from stems of symptomatic seedlings. No symptoms were observed on seedlings of Pseudotsuga menziesii, P. sylvestris, P. excelsa, and P. nigra or on control seedlings. In Europe, pitch canker caused by F. circinatum previously has been reported only in Spain on P. radiata and P. pinaster (1). There was an unconfirmed report of this disease in Italy ( http://www.eppo.org ), but to our knowledge, this is the first definite conclusive evidence of the presence of pitch canker of pine in Italy.

Violacein: properties and biological activities

The violet pigment violacein is an indole derivative, isolated mainly from bacteria of the genus Chromobacterium, which exhibits important antitumoral, antimicrobial and antiparasitary properties. Furthermore, the formulation of violacein in different polymeric carriers developed so far offers alternative approaches to overcoming physiological barriers and undesirable physicochemical properties in vivo, thus improving its efficacy.

Characterization of Fusarium oxysporum Isolated from Paprika in Korea

In the present study we first report in Korea the identification and characterization of Fusarium oxysporum isolated from rotten stems and roots of paprika (Capsicum annuum var. grossum) at Masan, Kyungsangnamdo in 2006. The fungal species produced white aerial mycelia accompanying with dark violet pigment on PDA. The optimal temperature and pH for the growth of the species was 25°C and pH 7, respectively. Microscopic observation of one of isolates of the species shows that its conidiophores are unbranehed and monophialides, its microconidia have oval-ellipsoidal shape with no septate and are of 3.0~11 × 1.5~3.5 μm sizes, its macroconidia are of 15~20 × 2.0~3.5 μm sizes and have slightly curved or slender shape with 2–3 septate. The results of molecular analysis show that the ITS rDNA of oxysporum from paprika shares 100% sequence identity with that of known F. oxysporum isolates. The identified species proved it’s pathogenicity by causing rotting symptom when it was inoculated on paprika fruits. The growth of F. oxysporum from paprika was suppressed on PDA by agrochemicals such as benomyl, tebueonazole and azoxystrobin. The identified species has the ability of producing extracelluar enzymes that degrade cellobiose and pectin.

Selection of dispersants for the dispersion of C.I. Pigment Violet 23 in organic medium

The dispersion of the organic carbazole violet pigment (C.I. Pigment Violet 23) in organic solvent requires the use of dispersant additives. Three carboxylic dispersants have been investigated regarding this purpose. Their adsorption behaviour has been evaluated by means of adsorption isotherms and the molecular interactions taking place at the surface have been inferred from 13C NMR spectroscopy. The rheological behaviour of the dispersions has considerably been improved by the presence of the dispersants. In particular, the copolymer dispersant that adsorbs the most strongly reduces the suspension viscosity and allows to increase the pigment loading by 50% keeping the rheological properties. The consequences of deflocculation of the suspension on the colorimetric properties are an enhanced tinting strength and an improved colour stability.

New violet 3,3′-bipyridyl pigment purified from deep-sea microorganism Shewanella violacea DSS12

We have purified a new violet pigment derived from Shewanella violacea DSS12 to determine its chemical structure. The pigment colored blue in tetrahydrofuran (THF) or chloroform and showed a broad absorption spectrum from 500 to 700 nm. X-ray diffraction analysis of single crystals showed that the chemical structure of this pigment was 5,5'-didodecylamino-4,4'-dihydroxy-3,3'-diazodiphenoquinone-(2,2'), containing the same chromophore as an indigoidine known as microbial blue pigment. The violet color of this pigment was due to hypsochromic shift (blue shift) caused by the side-by-side orientation of this pigment molecule, revealed by X-ray structural analyses of a single crystal.

Antioxidant properties of violacein: Possible relation on its biological function

Violacein, a violet pigment produced by Chromobacterium violaceum, has attracted much attention in recent literature due to its pharmacological properties. In this work, the antioxidant properties of violacein were investigated. The reactivity with oxygen and nitrogen reactive species and 1,1-diphenyl-2-picryl-hydrazyl (DPPH), a stable free radical, was evaluated. EPR studies were carried out to evaluate the reactivity with the hydroxyl radical. The action of violacein against lipid peroxidation in three models of lipid membranes, including rat liver microsomes, Egg and Soy bean phosphathidylcholine liposomes were also evaluated. The compound reacted with DPPH (IC 50 = 30 μM), nitric oxide (IC 50 = 21 μM), superoxide radicals (IC 50 = 125 μM) and decreased the hydroxyl radical EPR signal. The compound protected the studied membranes against peroxidation induced by reactive species in the micromolar range. The reconstitution of violacein into the membranes increased its antioxidant effect. These results indicate that the compound has strong antioxidant potential. Based on these results we suggest violacein plays an important role with the microorganism membrane in defense against oxidative stress.

Production and properties of the native Chromobacterium violaceum fucose-binding lectin (CV-IIL) compared to homologous lectins of Pseudomonas aeruginosa (PA-IIL) and Ralstonia solanacearum (RS-IIL)

Chromobacterium violaceum is a versatile, violet pigment (violacein)-producing beta-proteobacterium, confined to tropical and subtropical regions, dwelling in soil and water, like Pseudomonas aeruginosa and Ralstonia solanacearum. These three bacteria are saprophytes that occasionally become aggressive opportunistic pathogens virulently attacking animals (the first two) and plants (the third). The recent availability of their genome sequences enabled identification in the C. violaceum genome of an ORF (locus no. 1744) that is similar to those of P. aeruginosa and R. solanacearum lectins, PA-IIL and RS-IIL, respectively. A recombinant protein, CV-IIL, encoded by that ORF exhibited fucose>mannose-specific lectin activity resembling PA-IIL. This paper describes production and properties of the native CV-IIL, which, like PA-IIL and RS-IIL, is probably also a quorum-sensing-driven secondary metabolite, appearing concomitantly with violacein. Its formation is repressed in the CV026 mutant of C. violaceum, which lacks endogenous N-acylhomoserine lactone. The upstream extragenic sequence of its ORF contains a 20 bp sequence (5'-101-120) with partial similarities to the luxI-box and the related P. aeruginosa and R. solanacearum promoter boxes of quorum-sensing-controlled genes. The lectin level is augmented by addition of trehalose to the medium. The subunit size of CV-IIL (around 11.86 kDa) is similar to those of PA-IIL (11.73 kDa) and RS-IIL (11.60 kDa). Like PA-IIL, in the tetrameric form CV-IIL preferentially agglutinates alpha1-2 fucosylated H-positive human erythrocytes (regardless of their A, B or O type), as opposed to the O(h) Bombay type, but differs from it in having no interaction with rabbit erythrocytes and in displaying stronger affinity to l-galactose than to l-fucose. The greater similarity of CV-IIL to PA-IIL than to RS-IIL might be related to the selective adaptation of both C. violaceum and P. aeruginosa to animal tissues versus the preferential homing of R. solanacearum to plants.

Tertiary structure and spectral tuning of UV and violet pigments in vertebrates

Many vertebrate species use ultraviolet (UV) vision for such behaviors as mating, foraging, and communication. UV vision is mediated by UV-sensitive visual pigments, which have the wavelengths of maximal absorption ( λ max) at ∼360 nm, whereas violet (or blue) vision is mediated by orthologous pigments with λ max values of 390–440 nm. It is widely believed that amino acids in transmembrane (TM) I–III are solely responsible for the spectral tuning of these SWS1 pigments. Recent molecular analyses of SWS1 pigments, however, show that amino acids in TM IV–VII are also involved in the spectral tuning of these pigments through synergistic interactions with those in TM I–III. Comparisons of the tertiary structures of UV and violet pigments reveal that the distance between the counterion E113 in TM III and amino acid sites 87–93 in TM II is narrower for UV pigments than for violet pigments, which may restrict the access of water molecules to the Schiff base pocket and deprotonate the Schiff base nitrogen. Both mutagenesis analyses of E113Q and quantum chemical calculations strongly suggest that unprotonated Schiff base-linked chromophore is responsible for detecting UV light.

Genetic Basis of Spectral Tuning in the Violet-Sensitive Visual Pigment of African Clawed Frog, Xenopus laevis

Ultraviolet (UV) and violet vision in vertebrates is mediated by UV and violet visual pigments that absorb light maximally (lambdamax) at approximately 360 and 390-440 nm, respectively. So far, a total of 11 amino acid sites only in transmembrane (TM) helices I-III are known to be involved in the functional differentiation of these short wavelength-sensitive type 1 (SWS1) pigments. Here, we have constructed chimeric pigments between the violet pigment of African clawed frog (Xenopus laevis) and its ancestral UV pigment. The results show that not only are the absorption spectra of these pigments modulated strongly by amino acids in TM I-VII, but also, for unknown reasons, the overall effect of amino acid changes in TM IV-VII on the lambdamax-shift is abolished. The spectral tuning of the contemporary frog pigment is explained by amino acid replacements F86M, V91I, T93P, V109A, E113D, L116V, and S118T, in which V91I and V109A are previously unknown, increasing the total number of critical amino acid sites that are involved in the spectral tuning of SWS1 pigments in vertebrates to 13.

A second Micarea with a hypothecial K+ violet pigment

Micarea hypoviolascens sp. nov. (Pilocarpaceae) is described from an ancient woodland in western Scotland. It is the second species within Micarea known to have the olivaceous, K+ deep violet pigment (Sedifolia-grey) in the hypothecium.

Determination of the structure of the violet pigment C22H12Cl2N6O4 from a non-indexed X-ray powder diagram

The violet pigment methylbenzimidazolonodioxazine, C22H12Cl2N6O4 (systematic name: 6,14-dichloro-3,11-dimethyl-1,3,9,11-tetrahydro-5,13-dioxa-7,15-diazadiimidazo-[4,5-b:4',5'-m]pentacene-2,10-dione), shows an X-ray powder diagram consisting of only ca 12 broad peaks. Indexing was not possible. The structure was solved by global lattice energy minimizations. The program CRYSCA [Schmidt & Kalkhof (1999), CRYSCA. Clariant GmbH, Pigments Research, Frankfurt am Main, Germany] was used to predict the possible crystal structures in different space groups. By comparing simulated and experimental powder diagrams, the correct structure was identified among the predicted structures. Owing to the low quality of the experimental powder diagram the Rietveld refinements gave no distinctive results and it was difficult to prove the correctness of the crystal structure. Finally, the structure was confirmed to be correct by refining the crystal structure of an isostructural mixed crystal having a better X-ray powder diagram. The compound crystallizes in P1, Z=1. The crystal structure consists of a very dense packing of molecules, which are connected by hydrogen bridges of the type N-H...O=C. This packing explains the observed insolubility. The work shows that crystal structures of molecular compounds may be solved by lattice energy minimization from diffraction data of limited quality, even when indexing is not possible.

Waste reduction system for production of useful materials from un-utilized bamboo using steam explosion followed by various conversion methods

A waste reduction system for the production of useful materials from un-utilized plant biomass was developed for zero emission using a steam explosion, extraction and separation, and various conversion methods. This system utilizes a significant conversion approach without generating pollutants, i.e., waste gas, wastewater, and solid waste materials. The conversion of un-utilized bamboo ( Phyllostachys pubescens) into useful materials was studied for the effective utilization of its components such as holocellulose, water-soluble material, methanol-soluble lignin, and Klason lignin. These components were converted into useful materials, i.e., lactic acid, antibacterial violet pigment, methane gas, monosaccharides and oligosaccharides, epoxy resin without estrogenic activity, or activated carbon. The amount of useful materials and products produced from each component was estimated, and the reduction in the amount of pollutants generated in their production process and waste treatment and the detoxification of the lignin resin were confirmed.