Chemistry Central Journal - Latest Articles

Measurement of volatile organic compounds emitted in libraries and archives: An inferential indicator of paper decay?

Lorraine Gibson — 2012-05-15T00:00:00Z

Background; A sampling campaign of indoor air was conducted to assess the typical concentration of indoor air pollutants in 8 National Libraries and Archives across the U.K. and Ireland. At each site, two locations were chosen that contained various objects in the collection (paper, parchment, microfilm, photographic material etc.) and one location was chosen to act as a sampling reference location (placed in a corridor or entrance hallway). Results and Discussion; Of the locations surveyed, no measurable levels of sulfur dioxide were detected and low formaldehyde vapour (< 18 ug m-3) was measured throughout. Acetic and formic acids were measured in all locations with, for the most part, higher acetic acid levels in areas with objects compared to reference locations. A large variety of volatile organic compounds (VOCs) was measured in all locations, in variable concentrations, however furfural was the only VOC to be identified consistently at higher concentration in locations with paper-based collections, compared to those locations without objects. To cross-reference the sampling data with VOCs emitted directly from books, further studies were conducted to assess emissions from paper using solid phase microextraction fibres (SPME) fibres and a newly developed method of analysis; collection of VOCs onto a polydimethylsiloxane (PDMS) elastomer strip. Conclusions; In this study acetic acid and furfural levels were consistently higher in concentration when measured in locations which contained paper-based items. It is therefore suggested that both acetic acid and furfural (possibly also trimethylbenzenes, ethyltoluene, decane and camphor) may be present in the indoor atmosphere as a result of cellulose degradation and together may act as an inferential non-invasive marker for the deterioration of paper. Direct VOC sampling was successfully achieved using SPME fibres and analytes found in the indoor air were also identified as emissive by-products from paper. Finally a new non-invasive, method of VOC collection using PDMS strips was shown to be an effective, economical and efficient way of examining VOC emissions directly from the pages of a book and confirmed that toluene, furfural, benzaldehyde, ethylhexanol, nonanal and decanal were the most concentrated VOCs emitted directly from paper measured in this study.

Synthesis of naringin 6-ricinoleate using immobilized lipase

Veronica Almeida — 2012-05-11T00:00:00Z

Background: Naringin is an important flavanone with several biological activities, including antioxidant action. However, this compound shows low solubility in lipophilic preparations, such as is used in the cosmetic and food industries. One way to solve this problem is to add fatty acids to the flavonoid sugar unit using immobilized lipase. However, there is limited research regarding hydroxylation of unsaturated fatty acids as an answer to the low solubility challenge. In this work, we describe the reaction of naringin with castor oil containing ricinoleic acid, castor oil's major fatty acid component, using immobilized lipase from Candida antarctica. Analysis of the 1H and 13 C NMR (1D and 2D) spectra and literature comparison were used to characterise the obtained acyl derivative. Results: After allowing the reaction to continue for 120 hours (in acetone media, 50degreesC), the major product obtained was naringin 6"-ricinoleate. In this reaction, either castor oil or pure ricinoleic acid was used as the acylating agent, providing a 33% or 24% yield, respectively. The chemical structure of naringin 6"-ricinoleate was determined using NMR analysis, including bidimensional (2D) experiments. Conclusion: Using immobilized lipase from C. antarctica, the best conversion reaction was observed using castor oil containing ricinoleic acid as the acylating agent rather than an isolated fatty acid.

Immobilization of tris(2 pyridyl) methylamine in PVC-membrane sensor and characterization of the membrane properties

Majid Rezayi — 2012-05-07T00:00:00Z

Due to the increasing industrial use of titanium compounds, its determination is the subject of considerable efforts. The ionophore or the membrane active recognition is the most important component of any polymeric membrane sensor. The sensor respond depends on the ionophore and bonding between the ionophore and the target ion. Ionophores with molecule-sized dimensions containing cavities or semi-cavities can surround the target ion. The bond between ionophore and target ion gives different selectivity and sensitivity toward the other ions. Therefore, ionophores with different binding strengths can be used in the sensor. In the present work, poly(vinyl chloride) (PVC) based membrane incorporating tris(2 pyridyl) methylamine (tpm) as an ionophore have been prepared and explored as a titanium(III) selective sensor. The strengths of the ion-ionophore (Ti(OH)2+-tpm) interactions and the role of ionophore on membrane was performed by various techniques such as elemental analysis, UV-Vis, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and powder X-ray diffraction (XRD). All data approve the successful incorporation of organic group via covalent bond.

New lanostane-type triterpene acids from wolfiporia extensa

Gaimei She — 2012-05-06T00:00:00Z

Three new lanostane-type triterpene acids, 3-epi-benzoyloxyl-dehydrotumulosic acid (1), 3-epi-(3'-O-methyl malonyloxy)-dehydrotumulosic acid (2) and 3-epi-(3'-hydroxy-3'-methylglutaryloxyl)-dehydrotumulosic acid (3), were isolated from the sclerotia of Wolfiporia extensa, together with 3 known lanostane derivatives (4-6). Their structures were elucidated on the basis of spectroscopic analysis, including 1D and 2D-NMR techniques.

Essential oils from Leptospermums of the Sunshine Coast and northern rivers regions

Sarah Windsor — 2012-05-06T00:00:00Z

Background: Around the turn of this century, the oil yield and chemical composition of Australian Leptospermum species was analysed. Since that time, research has been focused on their use as phytomedicines. The oil yield and composition of essential oils from Australian Leptospermum species directly impacts their commercialisation for medicinal use. Results: The essential oils from Leptospermum (L.) juniperinum, L. laevigatum, L. liversidgei, L. polygalifolium, L. semibaccatum, L. speciosum, L. trinervium and L. whitei have been examined from specimens in the Sunshine Coast (Queensland) and Northern Rivers (New South Wales) Regions. Both chemotypes of L. liversidgei were observed. However, only chemotype II of L. semibaccatum and chemotype I of L. trinervium were identified. The only subspecies observed of L. polygalifolium was L. polygalifolium wallum. Conclusions: L. liversidgei chemotypes I and II have the potential for phytomedical use as antibacterial or antiinflammatory agents. Chemotype I has the potential for use as an insect repellent and chemotype II may provideantifungal activity.

New monocyclic monoterpenoid glycosides from Mentha haplocalyx Briq.

Gaimei She — 2012-05-06T00:00:00Z

Two new monocyclic monoterpenoid glycosides, rel-(1R,2S,3R,4R) p-menthane-1,2,3-triol 3-O--D-glucopyranoside (1) and rel- (1S,2R,3S) terpinolene-1,2,3-triol 3-O--D-glucopyranoside (2) were isolated from aqueous acetone extract of the aerial parts of Mentha haplocalyx. Their structures were elucidated through spectral analysis using MS and NMR spectrometers.

New Spectrofluorimetric Methods for Determination of Melatonin in the Presence of N-{2-[1-({3-[2-(acetylamino)ethyl]-5-methoxy-1H-indol-2-yl}methyl)-5-methoxy-1H-indol-3-yl]- ethyl}acetamide: A Contaminant in Commercial Melatonin Preparations

Hany Darwish — 2012-05-02T00:00:00Z

Melatonin (MLT) has many health implications, therefore it is of valuable importance to develop specific analytical methods for determination of MLT in the presence of its main contaminant, N-{2-[1-({3-[2-(acetylamino)ethyl]-5-methoxy-1H-indol-2-yl}methyl)-5-methoxy-1H-indol-3-yl]ethyl}acetamide (10). This work describes simple, sensitive, and reliable second derivative spectrofluorimetric method in addition to two multivariate calibration methods, principal component regression (PCR) and partial least square (PLS), for the determination of MLT in the presence of compound 10. For development of these analytical methods, compound 10 had to be prepared in an adequate amount. Thus, compound 10 was synthesized in six steps starting from 5-methoxyindole-2-carboxylic acid (1). Analytical performance of the proposed spectrofluorimetric methods was statistically validated with respect to linearity, accuracy, precision and specificity. The proposed methods were successfully applied for the assay of MLT in laboratory prepared mixtures containing up to 60 % of compound 10 and in commercial MLT tablets with recoveries not less than 99.00 %. No interference was observed from common pharmaceutical additives and the results were favorably compared with those obtained by a reference method.

Evaluation of Biologically Active Compounds from Calendula officinalis Flowers using Spectrophotometry

Monica Butnariu — 2012-04-27T00:00:00Z

Background: This study aimed to quantify the active biological compounds in C. officinalis flowers. Based on the active principles and biological properties of marigolds flowers reported in the literature, we sought to obtain and characterize the molecular composition of extracts prepared using different solvents. The antioxidant capacities of extracts were assessed by using spectrophotometry to measure both absorbance of the colorimetric free radical scavenger 2,2-diphenyl-1-picrylhydrazyl (DPPH) as well as the total antioxidant potential, using the ferric reducing power (FRAP) assay. Results: Spectrophotometric assays in the ultraviolet-visible (UV-VIS) region enabled identification and characterization of the full range of phenolic and flavonoids acids, and high-performance liquid chromatography (HPLC) was used to identify and quantify phenolic compounds (depending on the method of extraction). Methanol ensured more efficient extraction of flavonoids than the other solvents tested.Antioxidant activity in methanolic extracts was correlated with the polyphenol content. Conclusions: The UV-VIS spectra of assimilator pigments (e.g. chlorophylls), polyphenols and flavonoids extracted from the C. officinalis flowers consisted in quantitative evaluation of compounds which absorb to wavelengths broader than 360 nm.

Chemical consequences of cutaneous photoageing

Sarah Thurstan — 2012-04-25T00:00:00Z

Human skin, in common with our other organs, ages as a consequence of the passage of time, but in areas exposed to solar ultraviolet radiation, the effects of this intrinsic ageing process are exacerbated. In particular, both the severity and speed of onset of age-related changes, such as wrinkle formation and loss of elasticity, are enhanced in photoaged (also termed extrinsically aged) as compared with photoprotected aged skin. The anatomy of skin is characterised by two major layers: an outer, avascular, yet highly cellular and dynamic epidermis and an underlying vascularised, comparatively static and cell-poor, dermis. The structural consequences of photoageing are mainly evident in the extracellular matrix-rich but cell-poor dermis where key extracellular matrix proteins are particularly susceptible to photodamage. Most investigations to date have concentrated on the cell as both a target for and mediator of ultraviolet radiation-induced photoageing. As the main effectors of dermal remodelling produced by cells (extracellular proteases) generally have low substrate specificity, we recently suggested that the differential susceptibility of key extracellular matrix proteins to the processes of photoageing may be due to direct, as opposed to cell-mediated, photodamage.In this review, we discuss the experimental evidence for ultraviolet radiation (and related reactive oxygen species)-mediated differential degradation of normally long lived dermal proteins including the fibrillar collagens, elastic fibre components, glycoproteins and proteoglycans. Whilst these components exhibit highly diverse primary and hence macro- and supra-molecular structures we present evidence that amino acid composition alone may be a useful predictor of age-related protein degradation in both photoexposed and, as a consequence of differential oxidation sensitivity, photoprotected tissues.

Oxygen radical-mediated oxidation reactions of a simple alanine peptide motif -Density functional theory and transition state theory study

Hsing-Yu Chen — 2012-04-24T00:00:00Z

Background: Oxygen-base (O-base) oxidation in protein backbone is important in the protein backbone fragmentation due to the attack from reactive oxygen species (ROS). In this study, an alanine peptide was used model system to investigate this O-base oxidation by employing density functional theory (DFT) calculations combining with continuum solvent model. Detailed reaction steps were analyzed along with their reaction rate constants. Results: Most of the O-base oxidation reactions for this alanine peptide are exothermic except for the bond-breakage of the Cα-N bond to form hydroperoxy alanine radical. Among the reactions investigated in this study, the activated energy of OH α-H abstraction is the lowest one, while the generation of alkylperoxy peptide radical must overcome the highest energy barrier. The aqueous situation facilitates the oxidation reactions to generate hydroxyl alanine peptide derivatives except for the fragmentations of alkoxyl alanine peptide radical. The Cα-Cβ bond of the alkoxyl alanine peptide radical is more labile than the peptide bond. Conclusion: the rate-determining step of oxidation in protein backbone is the generation of hydroperoxy peptide radical via the reaction of alkylperoxy peptide radical with HO2. The stabilities of alkylperoxy peptide radical and complex of alkylperoxy peptide radical with HO2 are crucial in this O-base oxidation reaction.