Hyperbranched polymers as a novel class of pigment dispersants

Hyperbranched polymers form a novel class of materials that are employed as components of resin formulations. They are appreciated for their low intrinsic viscosities, which is ascribed to their spherical shape. It was envisaged to devise pigment dispersants with hyperbranched moieties as structural elements. Commercially available hyperbranched polymers with polyester, polyesteramide and polyethylene imine backbones were chemically modified to develop a range of disperants with core- and shell-type pigment anchoring mechanisms. Both the shell- and core-type anchoring principles generally can be used for pigment dispersion and stabilisation at a low viscosity level.     

Morin hydrate as pro-ecological antioxidant and pigment for polyolefin polymers

In our studies, we propose the use of natural, pro-ecological substances, such as flavonoids to protect elastomers against ageing. One of these substances, namely morin hydrate, was incorporated into ethylene–octene rubbers (Engage); then the vulcanisates of Engage containing the antioxidant under investigation were subjected to ageing processes. The changes in deformation energy, colour and cross-linking density and OIT index of the vulcanisates of Engage were measured before and after each ageing process. The test results obtained show that morin hydrate has a very positive influence on the stability of the vulcanisates of Engage, protecting them against the negative effects of ageing. In addition to its anti-oxidative function, morin hydrate changes the colour of the final polymeric product, fulfilling the role of a natural pigment. Thus, morin hydrate is not only a natural antioxidant but also a pigment in the polymers, imparting to them the features of pro-ecological materials.     

Honey: a novel antioxidant

The global prevalence of chronic diseases such as diabetes mellitus, hypertension, atherosclerosis, cancer and Alzheimer's disease is on the rise. These diseases, which constitute the major causes of death globally, are associated with oxidative stress. Oxidative stress is defined as an "imbalance between oxidants and antioxidants in favor of the oxidants, potentially leading to damage". Individuals with chronic diseases are more susceptible to oxidative stress and damage because they have elevated levels of oxidants and/or reduced antioxidants. This, therefore, necessitates supplementation with antioxidants so as to delay, prevent or remove oxidative damage. Honey is a natural substance with many medicinal effects such as antibacterial, hepatoprotective, hypoglycemic, reproductive, antihypertensive and antioxidant effects. This review presents findings that indicate honey may ameliorate oxidative stress in the gastrointestinal tract (GIT), liver, pancreas, kidney, reproductive organs and plasma/serum. Besides, the review highlights data that demonstrate the synergistic antioxidant effect of honey and antidiabetic drugs in the pancreas, kidney and serum of diabetic rats. These data suggest that honey, administered alone or in combination with conventional therapy, might be a novel antioxidant in the management of chronic diseases commonly associated with oxidative stress. In view of the fact that the majority of these data emanate from animal studies, there is an urgent need to investigate this antioxidant effect of honey in human subjects with chronic or degenerative diseases.     

Extraction and partial characterisation of antioxidant pigment produced by Chryseobacterium sp. kr6

Pigments synthesised by Chryseobacterium sp. kr6 growing on feather waste were extracted and characterised. The pigment extract was characterised by KOH test, UV–vis, CIELAB colour system, HPLC-DAD-MS, FTIR and its antioxidant capacity was evaluated. A positive bathochromic shift was observed when kr6 colonies or pigment extracts were subjected to alkaline solution (20% KOH) and a λ_max at 450 nm was detected for acetone extracts, although no typical fine structure of carotenoids was detected in the electomagnetic spectra. The HPLC profile of the extracted pigment showed that the compound has three different peaks with λ_max near 450 nm. The FTIR analysis shows some principal functional groups from a flexirubin-like molecule. The pigmented compound also presents antioxidant activity evaluated by the scavenging of the ABTS radical.     

石楠叶红、绿色素成分比较及抗氧化活性研究

采用多溶剂筛选最佳提取溶剂;以紫外分光光度法、高效液相色谱法、红外光谱法系统比较石楠红、绿色素成分的差别;同时考察红、绿色素对DPPH·清除能力、还原Fe3+能力和清除·OH自由基能力。结果以90%乙醇和乙酸乙酯-乙醇(1∶1)提取红色素、绿色素效果较好;通过显色反应、紫外光谱、红外光谱鉴别和高效液相色谱分析,基本确定红色素成分为黄酮类,绿色素成分为叶绿素类。抗氧化实验结果表明,在达到最大浓度0.34mg·m L-1时,石楠叶红、绿色素和维生素C对DPPH·清除率依次为79.6%,70.8%,66.9%,红、绿色素对·OH自由基的清除率依次为67.1%,51.2%,且红色素还原Fe3+能力较强。     

Mechanisms of antioxidant action: The behaviour of a bound antioxidant as an antiozonant

A rubber reactive antioxidant, 4-(mercapto acetamido)diphenylamine (I, MADA) was found to be more effective as an antiozonant when prereacted with the rubber chain (MADA-B) than when present as a conventional compounding ingredient (MADA-A) at the same molar concentration. In bound form after extraction MADA-B is as effective as an unextracted commercial antiozonant, iso-propylaminodiphenylamine (IPPD), at the same molar concentration. This result casts some doubt on the currently accepted view that antiozonants must migrate to the surface of the rubber in order to exert their protective effect.     

Effects of photodegradation on the physical and antioxidant properties of melanosomes isolated from retinal pigment epithelium

Melanosomes of the retinal pigment epithelium (RPE) are relatively long-lived organelles that are theoretically susceptible to changes induced by exposure to visible light. Here melanosomes were isolated from porcine RPE cells and subjected to high intensity visible light to determine the effects of illumination on melanosome structure and on the content and antioxidant properties of melanin. As compared to untreated melanosomes, illuminated granules showed morphologic changes consistent with photodegradation, which included variable reductions in electron density demonstrated by transmission electron microscopy (TEM), and particle fragmentation and surface disruption revealed by scanning electron microscopy (SEM) and atomic force microscopy. Illuminated melanosomes had lower melanin content, indicated by measures of absorbance and electron spin resonance (ESR) signal intensity, and reduced ability to bind iron, shown by chemical and ESR analyses. Compared to untreated melanosomes, ESR-spin trapping analyses further indicated that illuminated melanosomes show increased photogeneration of superoxide anion and reduced ability to inhibit the iron ion-catalyzed free radical decomposition of hydrogen peroxide. It appears therefore that visible light irradiation can disrupt the structure of RPE melanosomes and reduce the amount and antioxidant properties of melanin. Some of these changes occur in human RPE melanosomes with aging and the results obtained here suggest that visible light irradiation is at least partly responsible. The consequence of light-induced changes in RPE melanosomes may be a diminished capacity of melanin to help protect aged cells from oxidative damage, perhaps increasing the risk of diseases with an oxidative stress component such as age-related macular degeneration.     

一种半受阻酚类抗氧剂中间体的合成及抗氧化性能研究

采用2-甲基-6-叔丁基苯酚和丙烯酸甲酯为原料,通过迈克尔加成反应合成半受阻酚类抗氧剂中间体β-(3-甲基-5-叔丁基-4-羟基苯基)丙酸甲酯.条件优化实验确定该抗氧剂中间体的最佳合成工艺条件为:2-甲基-6-叔丁基苯酚与丙烯酸甲酯物质的量之比为1∶1.1,催化剂KOH与2-甲基-6-叔丁基苯酚的物质的量比为1∶10,丙烯酸甲酯滴加温度为90℃,丙烯酸甲酯滴加时间为30 min,反应温度为130℃,反应时间为5 h.在此条件下,半受阻酚类抗氧剂中间体β-(3-甲基-5-叔丁基-4-羟基苯基)丙酸甲酯的收率大于70%,熔程41.6℃~44.0℃.IR和1H NMR证实所合成目标产物的化学结构与其理论结构相一致.DPPH法测定半受阻酚类抗氧剂中间体清除自由基的性能,并与全受阻酚类抗氧剂中间体β-(3,5-二叔丁基-4-羟基苯基)丙酸甲酯进行对比.结果表明,由于邻位取代基的不对称效应,使得空间位阻较小的不对称抗氧剂中间体β-(3-甲基-5-叔丁基-4-羟基苯基)丙酸甲酯清除DPPH·的活性高于邻位取代基空间位阻较大的对称抗氧剂中间体清除DPPH·的活性.     

Mechanisms of antioxidant action: Formation of antioxidant adducts with rubbers through sulphur by a mechanochemical procedure

It is shown that antioxidants containing a thiol group can be mechanochemically reacted with both natural rubber (NR) and styrene-butadiene-rubber (SBR). Oxygen inhibits the reaction and the optimum temperature is in the region of 70°C. Increase in the antioxidant concentration in the rubber leads to increasing levels of adduct formation. Evidence is presented to show that although a substantial part of the adduct is formed during mechanochemical treatment, about 20% of the total binding occurs during the vulcanisation reaction.     

Mutagenic, antimutagenic and antioxidant activities of a new class of beta-glucoside hydroxyhydroquinone from Anagallis monelli growing in Tunisia

A new skeleton of an O-heteroside natural substance named zinolol, the first representative of a new class of aminated hydroxyhydroquinone, has been isolated from the whole plant Anagallis monelli. Its structure has been established by one and two dimensional NMR spectroscopic procedures. Antioxidant, mutagenic, antimutagenic activities were realised and positive results were recorded.     

Synthesis of a new catechin-pyrylium derived pigment

A new catechin-pyrylium derived pigment compound was synthesised from the reaction of catechin with sinapaldehyde in acidic conditions and its structure has been characterised by UV-vis, MS and NMR spectroscopy. Similar compounds could be expected to be formed in wines and contribute to changes in colour and astringency during ageing.     

Cupressuflavone,a new biflavonyl pigment

The leaves of Cupressus torulosa and C. sempervirens have been found to contain a new member of the biflavonyl group of natural colouring matters now named “cupressuflavone”. On the basis of colour reactions, UV, IR, NMR spectral data and degradation, its structure has been deduced as 8,8″-biapigeninyl and confirmed by comparison of the compound and its derivatives with synthetic samples.     

Lithol Red: a systematic structural study on salts of a sulfonated azo pigment

The first systematic series of single-crystal diffraction structures of azo lake pigments is presented (Lithol Red with cations=Mg(II), Ca(II), Sr(II), Ba(II), Na(I) and Cd(II)) and includes the only known structures of non-Ca examples of these pigments. It is shown that these commercially and culturally important species show structural behaviour that can be predicted from a database of structures of related sulfonated azo dyes, a database that was specifically constructed for this purpose. Examples of the successful structural predictions from the prior understanding of the model compounds are that 1) the Mg salt is a solvent-separated ion pair, whereas the heavier alkaline-earth elements Ca, Sr and Ba form contact ion pairs, namely, low-dimensional coordination complexes; 2) all of the Lithol Red anions exist as the hydrazone tautomer and have planar geometries; and 3) the commonly observed packing mode of alternating inorganic layers and organic bilayers is as expected for an ortho-sulfonated azo species with a planar anion geometry. However, the literature database of dye structures has no predictive use for organic solvate structures, such as that of the observed Na Lithol Red DMF solvate. Interestingly, the Cd salt is isostructural with the Mg salt and not with the Ca salt. It is also observed that linked eight-membered [MOSO](2) rings are the basic coordination motif for all of the known structures of Ca, Sr and Ba salts of sulfonated azo pigments in which competing carboxylate groups are absent.     

Mechanisms of antioxidant action: Chemical binding of a thiol antioxidant into polypropylene by means of uv irradiation

3,5-Di-t-butyl-4-hydroxybenzyl mercaptan (BHBM) became chemically combined to polypropylene to the extent of 68% of the antioxidant present when films containing BHBM were exposed to uv irradiation. In addition to the radical coupling reaction of the thiyl radical derived from BHBM with the polymer, a second technologically less useful process also occurs, leading to the formation of a derived stilbenequinone. The latter absorbs strongly both in the visible and in the near uv and consequently slows down the subsequent loss of the bound antioxidant from the polymer.     

Piperidines: a new class of urease inhibitors

A variety of piperidines (2-12, 14-26) with variable substituents at N-atoms have been synthesized and evaluated as urease inhibitors. The synthesized compounds showed varying degree of urease inhibitory activity ranging from 31.97 to 254 microM. The size and electron-donating or -withdrawing effects of substituents influence the activity, which lead to the formation of urease inhibitors.     

Tetraazaperopyrenes: a new class of multifunctional chromophores

Tetraazaperopyrene and a range of derivatives have been synthesised and their photophysical and redox-chemical properties studied. The parent compound, 1,3,8,10-tetraazaperopyrene (1), was prepared by treating 4,9-diamino-3,10-perylenequinone diimine with triethyl orthoformate, whereas the 2,9-disubstituted derivatives of 1 were obtained after treatment with the corresponding carboxylic acid chloride or anhydride (2 mol equiv). The 1,3,8,10-tetraazaperopyrene core structure was established by X-ray diffraction of 2,9-bis(2-bromophenyl)-1,3,8,10-tetraazaperopyrene (6). The UV-visible absorption spectra of the compounds have a characteristic visible pi(*)<--pi absorption band at 440 nm (log epsilon(max)=4.80) with a strong vibrational progression (Delta nu approximately 1450 cm(-1)). Diprotonation of the nitrogen atoms induces a bathochromic shift of this band from 430-440 to 470-480 nm and all four nitrogen atoms are protonated when pure H(2)SO(4) is used as the solvent. The first and second as well as the third and fourth protonations occur concomitantly, which implies that they have very similar pK(a) values and, consequently, similar proton affinities. A theoretical study of the proton affinities in the gas phase and in solution attributes this behaviour to the effects of polar solvents, which dampen the charge of a protonated site at the other end of the molecule and thus effectively decouple the two opposite pyrimidine units in the polycondensed aromatic compound. The photophysical data were modelled in a time-dependent DFT study of 1, 1H(2)(2+) and 1H(4)(4+) in both the gas phase and in a polar solvent. All the dyes show weak fluorescence in organic solvents, however, their protonated conjugate acids show dramatically increased fluorescence intensity. All of the dyes undergo two electrochemically reversible one-electron reductions with cyclovoltammetric half-wave potentials at E(red1) approximately -0.9 V and E(red2) approximately -1.3 V (vs. SCE), which are associated with characteristic spectral changes.     

Oligoindenopyrenes: a new class of polycyclic aromatics

A new class of polycyclic aromatic hydrocarbons--oligoindenopyrenes--has been synthesized featuring a Pd-catalyzed Suzuki-Heck coupling cascade. The oligoindenopyrenes are robust, highly colored substructures of C(70) and have properties that might prove useful in new organic materials or devices. After excitation, the tetraindenopyrene derivative 3d undergoes efficient deactivation (99%) by internal conversion to the ground state. The small fluorescence quantum yield (0.004) is in accordance with the short (0.6 ns) fluorescence decay time.     

Myrotoxins: a new class of macrocyclic trichothecenes

An isolate of $\text{Myrothecium roridum}$ which is a pathogen on tomatoes in Texas produces a new class of C27 macrocyclic trichothecenes which contains a nonconjugated diene system that includes a vinyl ether group.