Modulating the thermodynamics, kinetics and photochemistry of 7-diethylamino-4'-dimethylaminoflavylium in water/ethanol, SDS and CTAB micelles

The thermodynamics and kinetics of compound 7-diethylamino-4'-dimethylaminoflavylium were studied in water : ethanol (1 : 1) and water in the presence of SDS and CTAB micelles. The blue flavylium cation is in equilibrium with the pink protonated flavylium cation defined by pK_{AH²⁺/AH⁺} and the yellow trans-chalcone, defined by pK_AH⁺/Ct. The difference between these two pKs gives the pH domain of the flavylium cation, ΔpK = 1.95 in CTAB, ΔpK = 5.6 in water/ethanol (1 : 1) and ΔpK = 8.5 in SDS micelles. On the other hand, the pH domain of the trans-chalcone is limited by pK_AH⁺/Ct and pK_Ct/Ct^-. It is lower in SDS micelles ΔpK = 2.7, increases in ethanol/water (1 : 1) ΔpK = 5.1 and is maximum in CTAB micelles, ΔpK = 6.8. All these effects can be explained by the electric charge present at the micellar surface. Relative energy level diagrams that allow for the explanation of the driving forces for any pH stimuli or light absorption were constructed from the calculated equilibrium constants. Irradiation of the trans-chalcone at 466 nm leads to the formation of the flavylium cation. In water : ethanol (1 : 1), the photochemistry is residual with Φ < 0.00002, while in SDS micelles at pH = 7 light increases the rate of the spontaneous conversion of trans-chalcone to the flavylium cation, with quantum yield Φ = 0.002; photochromism from trans-chalcone to give the flavylium cation with the same quantum yield is also observed in CTAB micelles.

Photoactivated cell-killing amino-based flavylium compounds

Photodynamic therapy (PDT) is a well-established therapeutic for the treatment of different diseases. The growing interest of this technique required the development of new photosensitizers with better photo-features. This work reports the study of the potential of five nature-inspired amino-based flavylium compounds with different structural features as photosensitizers towards topical PDT. In terms of dark cytotoxicity the five pigments were tested towards confluent skin cells in both fibroblasts and keratinocytes. In the range of concentrations tested (6.3–100 μM), keratinocytes were more prone to growth inhibition and the IC₅₀ values for 5OH4′NMe₂, 7NEt₂st4′NMe₂ and 7NEt₂4′NH₂ were determined to be 47.3 ± 0.3 μM; 91.0 ± 0.8 μM and 29.8 ± 0.8 μM, respectively. 7NEt₂4′NMe₂, 7NEt₂st4′NMe₂ and 7NEt₂4′NH₂ showed significant fluorescence quantum yields (from 3.40 to 20.20%) and production of singlet oxygen (¹O₂). These latter chromophores presented IC₅₀ values of growth inhibition of keratinocytes between 0.9 and 1.5 µM, after 10 min of photoactivation with white light. This cellular damage in keratinocyte cells upon white light activation was accompanied with the production of reactive oxygen species (ROS). It was also found that the compounds can induce damage by either type I (ROS production) or type II (singlet oxygen) PDT mechanism, although a higher cell survival was observed in the presence of ¹O₂ quenchers. Overall, a structure–activity relationship could be established, ranking the most important functional groups for the photoactivation efficiency as follows: C7-diethylamino > C4′-dimethylamino > C2-styryl.

Anthocyanin-Related Pigments: Natural Allies for Skin Health Maintenance and Protection

Human skin is commonly described as a particularly dynamic and complex environment, with a physiological balance continuously orchestrated by numerous internal and external factors. Intrinsic aging, exposure to UV radiation and skin pathogens are some of the key players that account for dermatological alterations and ailments. In this regard, this study intended to explore the potential skin-health beneficial properties of a group of molecules belonging to the anthocyanin family: cyanidin- and malvidin-3-O-glucosides and some of their structurally related pigments, resulting in a library of compounds with different structural properties and color hues. The inclusion of both purified compounds and crude extracts provided some insights into their distinctive effects when tested as individual agents or as part of multicomponent mixtures. Overall, most of the compounds were found to reduce biofilm production by S. aureus and P. aeruginosa reference strains, exhibit UV-filter capacity, attenuate the production of reactive oxygen species in human skin keratinocytes and fibroblasts and also showed inhibitory activity of skin-degrading enzymes, in the absence of cytotoxic effects. Carboxypyranocyanidin-3-O-glucoside stood out for its global performance which, combined with its greater structural stability, makes this a particular interesting compound for potential incorporation in topical formulations. Results provide strong evidence of the skin protective effects of these pigments, supporting their further application for cosmeceutical purposes.

The Role of Anthocyanins, Deoxyanthocyanins and Pyranoanthocyanins on the Modulation of Tyrosinase Activity: An In Vitro and In Silico Approach

Tyrosinase is the central enzyme involved in the highly complex process of melanin formation, catalyzing the rate-limiting steps of this biosynthetic pathway. Due to such a preponderant role, it has become a major target in the treatment of undesired skin pigmentation conditions and also in the prevention of enzymatic food browning. Numerous phenolic-based structures from natural sources have been pointed out as potential tyrosinase inhibitors, including anthocyanins. The aim of the present study was to individually assess the tyrosinase inhibitory activity of eight purified compounds with a variable degree of structural complexity: native anthocyanins, deoxyanthocyanins, and pyranoanthocyanins. The latter two, the groups of anthocyanin-related compounds with enhanced stability, were tested for the first time. Compounds 1 to 4 (luteolinidin, deoxymalvidin, cyanidin-, and malvidin-3-O-glucoside) revealed to be the most effective inhibitors, and further kinetic studies suggested their inhibition mechanism to be of a competitive nature. Structure–activity relationships were proposed based on molecular docking studies conducted with mushroom tyrosinase (mTYR) and human tyrosinase-related protein 1 (hTYRP1) crystal structures, providing information about the binding affinity and the different types of interactions established with the enzyme’s active center which corroborated the findings of the inhibition and kinetic studies. Overall, these results support the applicability of these compounds as pigmentation modulators.

On the Limits of Anthocyanins Co-Pigmentation Models and Respective Equations

Anthocyanins co-pigmentation models with application on 1:1 complexes were revisited, and their limitations were critically commented. The flavylium multistate of species is dramatically simplified to a single acid-base equilibrium between flavylium cation and its conjugated base CB, equal to the sum of quinoidal base, hemiketal, and cis and trans-chalcones. Bearing this, a new equation that simultaneously allows calculation of the co-pigmentation constant with flavylium cation (K_AH+_CP) and with its conjugated base CB (K_CBCP) was deduced. This equation can be used at a fixed co-pigment concentration with pH as a variable or at fixed pH and co-pigment concentration variable. A global fitting of all data allows us to calculate both association constants with good accuracy. The model was applied to the co-pigmentation of malvidin-3-glucoside with caffeine and pentagalloyl glucose (PGG). Caffeine gives rise to complexes not only with flavylium cation K_AH+_CP = 125 ± 7 M^-1 but also with CB with K_CBCP = 23 ± 3 M^-1. PGG complexes exclusively with flavylium cation, K_AH+_CP = 914 ± 10 M^-1, and the possible interaction with quinoidal base is lower than the detection limits that the inherent experimental error permits.

Exploring the Applications of the Photoprotective Properties of Anthocyanins in Biological Systems

Due to their physical and chemical characteristics, anthocyanins are amongst the most versatile groups of natural compounds. Such unique signature makes these compounds a focus in several different areas of research. Anthocyanins have well been reported as bioactive compounds in a myriad of health disorders such as cardiovascular diseases, cancer, and obesity, among others, due to their anti-inflammatory, antioxidant, anti-diabetic, anti-bacterial, and anti-proliferative capacities. Such a vast number of action mechanisms may be also due to the number of structurally different anthocyanins plus their related derivatives. In this review, we highlight the recent advances on the potential use of anthocyanins in biological systems with particular focus on their photoprotective properties. Topics such as skin aging and eye degenerative diseases, highly influenced by light, and the action of anthocyanins against such damages will be discussed. Photodynamic Therapy and the potential role of anthocyanins as novel photosensitizers will be also a central theme of this review.

New records and range expansion of Chironius carinatus&nbsp;(Linnaeus, 1758) (Serpentes, Colubridae) from the state of Para&iacute;ba, northeast Brazil

The current work provides a new state record of the snake Chironius carinatus (Linnaeus, 1758) based on two specimens collected in the Atlantic Forest of Para&iacute;ba state, northeastern Brazil. This species occurs in the Amazon and Atlantic Forests. The new records fills in a gap in the species&rsquo; distribution on the Brazilian coast. In Para&iacute;ba, C. carinatus occurs in sympatry with two other Chironius Fitzinger, 1826 species, C. flavolineatus Jan, 1863 and C. exoletus (Linnaeus, 1758).

Impact of Lignosulfonates on the Thermodynamic and Kinetic Parameters of Malvidin-3- O-glucoside in Aqueous Solutions

The interaction of malvidin-3- O-glucoside (1) and a lignosulfonate was studied by UV-visible spectroscopy, and the results obtained showed the formation of a complex between the negatively charged lignosulfonate and the flavylium cation form (AH⁺) of this anthocyanin at pH 1. The thermodynamic and kinetic parameters of 1 in the presence of a lignosulfonate were determined by UV-visible spectroscopy and stopped-flow techniques. The main differences were observed in the flavylium cation (AH⁺)/quinoidal base (A) equilibrium, the AH⁺ form being more stabilized than A (p K_a1 = 4.4 ± 0.1) compared with 1 in the absence of the lignosulfonate (p K_a1 = 3.9 ± 0.1). Furthermore, comparing the hydration ( k_h = 0.028 s^-1) and dehydration ( k_-h = 40 M^-1 s^-1) processes of 1 in the presence of the lignosulfonate with the processes of 1 ( k_h = 0.12 s^-1 and k_-h = 35 M^-1 s^-1) show that the hydration process is slower while the dehydration process is practically unaffected in the presence of the lignosulfonate.

Malvidin 3-Glucoside-Fatty Acid Conjugates: From Hydrophilic toward Novel Lipophilic Derivatives

This work describes the lipophilization reactions of malvidin 3-glucoside with different saturated fatty acid chain lengths using an enzymatic synthesis and the study of their physical-chemical and antioxidant properties. The lipophilic anthocyanins were obtained with satisfactory yields (22-40%) after column chromatography purifications, and they revealed the same appealing chromatic features of the parent anthocyanin. All of the compounds were characterized by mass spectrometry, confirming the regioselective acylation on the glucose moiety. The octanol-water partition coefficients and the hydrophobicity index of the different derivatives were determined, confirming a lipophilicity increase concomitant with the fatty acid chain length. The antioxidant profile was also evaluated by using two in vitro methods (β-carotene-lineolate method and oxygen consumption assay). Overall, a maximum of antioxidant activity was achieved when malvidin 3-glucoside was conjugated with caprylic acid (C8). Altogether, the results obtained provide a good perspective for the technological application of these functionalized anthocyanins in the cosmetics and food industries.

High-pressure assisted extraction of bioactive compounds from industrial fermented fig by-product

High-pressure assisted extraction was employed to obtain fig by-product derived extracts and its impact was evaluated on antioxidant activity and total phenolic, tannin, and flavonoid. A Box-Behnken design was applied to evaluate the effects of pressure, extraction time and ethanol concentration on extractions and optimal conditions were estimated by response surface methodology. The correlation analysis of the mathematical-regression model indicated that a quadratic polynomial model could be employed to optimize the high pressure extraction of compounds. Only the models developed for total antioxidant activity by DPPH ^· and for total flavonoids presented coefficient determinations lower than 0.95. From response surface plots, pressure, extraction time and ethanol concentration showed independent and interactive effects. The optimal conditions included 600 MPa, an extraction time between 18 and 29 min, depending on the parameter analyzed and a low ethanol concentration (<15%) except for flavonoids (48%). High pressure led to an increase of 8-13% of antioxidant activity and an increase of 8-11% of total phenolics, flavonoids and tannins content when compared to extracts performed at 0.1 MPa. Analysis of variance indicated a high goodness of fit of the models used and the adequacy of response surface methodology for optimizing high pressure extraction.

A New Chemical Pathway Yielding A-Type Vitisins in Red Wines

A new chemical pathway yielding A-type vitisins in red wines is proposed herein from the reaction between anthocyanins and oxaloacetic acid (OAA). This new chemical path is thought to occur in the first stages of the wine production even during the fermentation process. This is due to the revealed high reactivity of OAA with anthocyanins compared with the already known precursor (pyruvic acid, PA). In model solutions at wine pH (3.5), when malvidin-3-O-glucoside (mv-3-glc) is in contact with OAA and PA a decrease in the OAA concentration is observed along with the formation of A-type vitisin. Moreover, part of the OAA is also chemically converted into PA in model solutions. The reaction yields were also determined for OAA and PA using different mv-3-glc:organic acid molar ratios (1:0.5, 1:1, 1:5, 1:10; 1:50, and 1:100) and these values were always higher for OAA when compared to PA, even at the lowest molar ratio (1:0.5). The reaction yields were higher at pH 2.6 in comparison to pH 1.5 and 3.5, being less affected at pH 3.5 for OAA. These results support the idea that OAA can be at the origin of A-type vitisins in the first stages of wine production and PA in the subsequent ageing process.

Electrochemical cell design for the impedance studies of chlorine evolution at DSA(®) anodes

A new electrochemical cell design suitable for the electrochemical impedance spectroscopy (EIS) studies of chlorine evolution on Dimensionally Stable Anodes (DSA(®)) has been developed. Despite being considered a powerful tool, EIS has rarely been used to study the kinetics of chlorine evolution at DSA anodes. Cell designs in the open literature are unsuitable for the EIS analysis at high DSA anode current densities for chlorine evolution because they allow gas accumulation at the electrode surface. Using the new cell, the impedance spectra of the DSA anode during chlorine evolution at high sodium chloride concentration (5 mol dm(-3) NaCl) and high current densities (up to 140 mA cm(-2)) were recorded. Additionally, polarization curves and voltammograms were obtained showing little or no noise. EIS and polarization curves evidence the role of the adsorption step in the chlorine evolution reaction, compatible with the Volmer-Heyrovsky and Volmer-Tafel mechanisms.

Evidence for copigmentation interactions between deoxyanthocyanidin derivatives (oaklins) and common copigments in wine model solutions

The aim of this study was to investigate interactions possibly taking place in red wine between oaklins, which are deoxyanthocyanidin derivatives (guaiacylcatechin-pyrylium and syringylcatechin-pyrylium), and several copigments: catechin (CP1), epicatechin (CP2), chlorogenic acid (CP3), epigallocatechin (CP4), and procyanidin B3 (CP5). The results show that oaklins, like common anthocyanins, also present copigmentation interactions that further stabilize the flavylium cation in hydroalcoholic solutions. Molecular dynamics simulations were also performed to interpret the binding data, to specify the relative arrangement of the pigment and copigment molecules within the complexes, and to interpret their absorption properties in the visible range.

Portuguese guidelines for the use of biological agents in rheumatoid arthritis - October 2011 update

The authors present the revised version of the Portuguese Society of Rheumatology (SPR) guidelines for the treatment of Rheumatoid Arthritis (RA) with biological therapies. In these guidelines the criteria for introduction and maintenance of biological agents are discussed as well as the contraindications and procedures in the case of nonresponders. Biological treatment (with a tumour necrosis factor antagonist, abatacept or tocilizumab) should be considered in RA patients with a disease activity score 28 (DAS 28) equal to or greater than 3.2 despite treatment with at least 20mg-weekly-dose of methotrexate (MTX) for at least 3 months or, if such treatment is not possible, after 3 months of other conventional disease modifying drug or combination therapy. A DAS 28 score between 2.6 and 3.2 with a significant functional or radiological deterioration under treatment with conventional regimens could also constitute an indication for biological treatment. The treatment goal should be remission or, if that is not achievable, at least a low disease activity, defined by a DAS28 lower than 3.2, without significative functional or radiological worsening. The response criteria, at the end of the first 3 months of treatment, are a decrease of at least 0.6 in the DAS28 score. After 6 months of treatment res­ponse criteria is defined as a decrease greater than 1.2 in the DAS28 score. Non-responders, in accordance to the Rheumatologist’s clinical opinion, should try a switch to another biological agent (tumour necrosis factor antagonist, abatacept, rituximab or tocilizumab).

The effects of glutaraldehyde on the control of single and dual biofilms of Bacillus cereus and Pseudomonas fluorescens

Glutaraldehyde (GLUT) was evaluated for control of single and dual species biofilms of Bacillus cereus and Pseudomonas fluorescens on stainless steel surfaces using a chemostat system. The biofilms were characterized in terms of mass, cell density, total and matrix proteins and polysaccharides. The control action of GLUT was assessed in terms of inactivation and removal of biofilm. Post-biocide action was characterized 3, 7, 12, 24, 48 and 72 h after treatment. Tests with planktonic cells were also performed for comparison. The results demonstrated that in dual species biofilms the metabolic activity, cell density and the content of matrix proteins were higher than those of either single species. Planktonic B. cereus was more susceptible to GLUT than P. fluorescens. The biocide susceptibility of dual species planktonic cultures was an average of each single species. Planktonic cells were more susceptible to GLUT than their biofilm counterparts. Biofilm inactivation was similar for both of the single biofilms while dual biofilms were more resistant than single species biofilms. GLUT at 200 mg l(-1) caused low biofilm removal (<10%). Analysis of the post-biocide treatment data revealed the ability of biofilms to recover their activity over time. However, 12 h after biocide application, sloughing events were detected for both single and dual species biofilms, but were more marked for those formed by P. fluorescens (removal >40% of the total biofilm). The overall results suggest that GLUT exerts significant antimicrobial activity against planktonic bacteria and a partial and reversible activity against B. cereus and P. fluorescens single and dual species biofilms. The biocide had low antifouling effects when analysed immediately after treatment. However, GLUT had significant long-term effects on biofilm removal, inducing significant sloughing events (recovery in terms of mass 72 h after treatment for single biofilms and 42 h later for dual biofilms). In general, dual species biofilms demonstrated higher resistance and resilience to GLUT exposure than either of the single species biofilms. P. fluorescens biofilms were more susceptible to the biocide than B. cereus biofilms.

Portuguese guidelines for the use of biological agents in rheumatoid arthritis - March 2010 update

The authors present the revised version of the Portuguese Society of Rheumatology (SPR) guidelines for the treatment of rheumatoid arthritis (RA) with biological therapies. In these guidelines the criteria for introduction and maintenance of biological agents are discussed as well as the contraindications and procedures in the case of non-responders. Biological treatment should be considered in RA patients with a disease activity score 28 (DAS 28) superior to 3.2 despite treatment with 20mg/week of methotrexate (MTX) for at least 3 months or, if such treatment is not possible, after 6 months of other conventional disease modifying drug or combination therapy. A DAS 28 score between 2.6 and 3.2 with a significant functional or radiological deterioration under treatment with conventional regimens could also constitute an indication for biological treatment. The treatment goal should be remission or, if that is not achievable, at least a low disease activity, characterized by a DAS28 lower than 3.2, without significative functional or radiological worsening. The response criteria, at the end of the first 3 months of treatment, are a decrease of 0.6 in the DAS28 score. After 6 months of treatment response criteria is defined as a decrease of more than 1.2 in the DAS28 score. Non-responders, in accordance to the Rheumatologist's clinical opinion, should try a switch to another biological agent (tumour necrosis factor antagonist, abatacept, rituximab or tocilizumab).

[Eosinophilic fasciitis and aplastic anemia]

Eosinophilic fasciitis is a rare rheumatic condition characterized by inflammatory thickening of the skin and fascia, peripheral eosinophilia, elevated erythrocyte sedimentation rate and hypergammaglobulinemia. Internal organ involvement is uncommon. It is often difficult to diagnose eosinophilic fasciitis and its course may be variable. Glucocorticoids are most commonly used in the treatment but in many cases they are ineffective, requiring combined immunosuppressive treatment. Several cases of eosinophilic fasciitis and serious haematological disorders such as immune thrombocytopenia, Hodgkin's disease and aplastic anaemia have been described. The authors report an atypical severe case of eosinophilic fasciitis complicated by aplastic anaemia non responsive to treatment.

Reduction of large neutral amino acid levels in plasma and brain of hyperleucinemic rats

Neurological dysfunction is common in patients with maple syrup urine disease (MSUD). However, the mechanisms underlying the neuropathology of this disorder are poorly known. In the present study we investigated the effect of acute hyperleucinemia on plasma and brain concentrations of amino acids. Fifteen-day-old rats were injected subcutaneously with 6 micromol L-leucine per gram body weight. Controls received saline in the same volumes. The animals were sacrificed 30--120 min after injection, blood was collected and their brain rapidly removed and homogenized. The amino acid concentrations were determined by HPLC using orthophtaldialdehyde for derivatization and fluorescence for detection. The results showed significant reductions of the large neutral amino acids (LNAA) L-phenylalanine, L-tyrosine, L-isoleucine, L-valine and L-methionine, as well as L-alanine, L-serine and L-histidine in plasma and of L-phenylalanine, L-isoleucine, L-valine and L-methionine in brain, as compared to controls. In vitro experiments using brain slices to study the influence of leucine on amino acid transport and protein synthesis were also carried out. L-Leucine strongly inhibited [14C]-L-phenylalanine transport into brain, as well as the incorporation of the [14C]-amino acid mixture, [14C]-L-phenylalanine and [14C]-L-lysine into the brain proteins. Although additional studies are necessary to evaluate the importance of these effects for MSUD, considering previous findings of reduced levels of LNAA in plasma and CSF of MSUD patients during crises, it may be speculated that a decrease of essential amino acids in brain may lead to reduction of protein and neurotransmiter synthesis in this disorder.