Determination of uronic acids in isolated hemicelluloses from kenaf using diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) and the curve-fitting deconvolution method

Hemicellulose samples were isolated from kenaf (Hibiscus cannabinus L.). Hemicellulosic fractions usually contain a variable percentage of uronic acids. The uronic acid content (expressed in polygalacturonic acid) of the isolated hemicelluloses was determined by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and the curve-fitting deconvolution method. A linear relationship between uronic acids content and the sum of the peak areas at 1745, 1715, and 1600 cm(-1) was established with a high correlation coefficient (0.98). The deconvolution analysis using the curve-fitting method allowed the elimination of spectral interferences from other cell wall components. The above method was compared with an established spectrophotometric method and was found equivalent for accuracy and repeatability (t-test, F-test). This method is applicable in analysis of natural or synthetic mixtures and/or crude substances. The proposed method is simple, rapid, and nondestructive for the samples.     

The effect of sowing date and growth stage on the essential oil composition of three types of parsley (Petroselinum crispum)

Essential oils obtained by simultaneous distillation–extraction (SDE) from leaves, petioles and roots of three types of parsley (turnip‐rooted, plain leaf and curly leaf type), sown on three different dates, were analysed by GC‐MS (gas chromatography–mass spectrometry) analysis. Parsley plants were found to produce mainly β‐phellandrene, 1,3,8‐p‐menthatriene, α‐,p‐dimethylstyrene, myristicin, β‐myrcene and apiole. In some cases α‐ and β‐pinene were also found, whereas β‐elemene was detected, especially in the curly leaf type. The growth stage, plant tissue and date of sowing, as well as the climate conditions, all had a significant effect on the essential oil composition by altering the ratio of the above substances. Copyright © 2004 Society of Chemical Industry     

Differentiation of saffron from four countries by mid-infrared spectroscopy and multivariate analysis

Mid-infrared spectroscopy combined with multivariate analysis has been applied for the discrimination of 250 saffron samples from Greece (40 samples), Iran (87 samples), Italy (60 samples) and Spain (63 samples). The infrared spectra of saffron filament samples and their organic extracts were recorded. Principal component analysis was applied to different spectral regions. Then the principal components were used as variables in discriminant analysis. The best discriminatory approach was achieved in the spectral region 2000–700 cm⁻¹. The spectral region responsible for the differentiation of Italian samples is in the region of carbonyl group around 1746 cm⁻¹. The spectral region at around 1600 cm⁻¹ and the band at 1670 cm⁻¹ are responsible for the differentiation of samples from the remaining countries. From the original grouped cases, 93.6% were correctly classified. The correct classification rates for saffron samples from Greece, Iran, Italy and Spain were 90.0, 89.5, 96.7 and 98.4%, respectively. The combination of infrared spectroscopic technique with multivariate analysis is a rapid and ambient method to discriminate saffron samples in terms of geographical origin.     

Identification and differentiation of goat and sheep milk based on diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) using cluster analysis

A new methodology for identification and differentiation of goat and sheep milk was developed based on FT-IR spectroscopy using hierarchical and discriminant analysis. Forty-nine goat and 38 sheep defatted and freeze-dried Greek milk samples were analyzed. FT-IR spectra were obtained in the diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) mode. The spectral region 1840–950 cm⁻¹ was used to ‘fingerprint’ milk types. Main peak used for differentiation of goat/sheep milk is located at 1745 cm⁻¹, which is correlated to the degree of sugars carboxyl methyl esterification. Hierarchical and discriminant analyses were based on the absorptions of the above spectral region. These analyses showed that the samples of goat milk can be differentiated from the samples of sheep’s.     

Solid-phase microextraction/gas-chromatographic/mass spectrometric analysis of p -dichlorobenzene and naphthalene in honey

Protection of honeycombs from the Wax moth, Galleria mellonella, involves the use of physical, biological or chemical control methods. As chemical control may result in residues in the extracted honey, the presence of p-dichlorobenzene and naphthalene residues was investigated by solid-phase microextraction (SPME) coupled to gas-chromatographic/mass spectrometry (GC/MS). The method was linear between 5 and 200 µg kg^–1 honey for p-dichlorobenzene and 1 and 200 µg kg^–1 for naphthalene. Limits of detection were 1 and 0.1 µg kg^–1, respectively, for p-dichlorobenzene and naphthalene, while relative standard deviations were 2.6 and 7.9%, respectively. Application of the method to 90 unifloral Greek honeys revealed that, in 25.6% of the samples, the concentration of either one of the pesticides exceeded the maximum residue level (MRL). Maximum concentrations were 163.03 µg kg^–1 honey for p-dichlorobenzene and 193.74 µg kg^–1 honey for naphthalene. Naphthalene was found in traceable amounts in 78.9% of the samples, but only 5.6% of them contained concentrations above the MRL, which indicates the use of pre-contaminated honeycomb foundations or built combs. Nevertheless, because naphthalene is naturally present in some plant species growing in Greece, the contribution of nectar from such a floral source should not be overlooked.     

Geographical differentiation of saffron by GC–MS/FID and chemometrics

The volatile compounds of saffron of different origins were investigated to check their suitability as markers of geographic differentiation. A total of 247 saffron samples from Greece (40 samples), Iran (84 samples), Italy (60 samples) and Spain (63 samples) which were harvested in 2006 were analysed using ultrasound-assisted extraction, gas chromatography followed by mass spectrometry and flame ionisation. All regions were easily differentiated by canonical discriminant analysis. The percentages of correct classification and validation were 96.4 and 94.3%, respectively. These investigations showed the potential of saffron volatiles to discriminate saffron samples with different geographical origins.     

Identification and Characterization of the Carbapenem MM 4550 and its Gene Cluster in Streptomyces argenteolus ATCC 11009

Nearly 50 naturally occurring carbapenem β‐lactam antibiotics, most produced by Streptomyces, have been identified. The structural diversity of these compounds is limited to variance of the C‐2 and C‐6 side chains as well as the stereochemistry at C‐5/C‐6. These structural motifs are of interest both for their antibiotic effects and their biosynthesis. Although the thienamycin gene cluster is the only active gene cluster publically available in this group, more comparative information is needed to understand the genetic basis of these structural differences. We report here the identification of MM 4550, a member of the olivanic acids, as the major carbapenem produced by Streptomyces argenteolus ATCC 11009. Its gene cluster was also identified by degenerate PCR and targeted gene inactivation. Sequence analysis revealed that the genes encoding the biosynthesis of the bicyclic core and the C‐6 and C‐2 side chains are well conserved in the MM 4550 and thienamycin gene clusters. Three new genes, cmmSu, cmm17 and cmmPah were found in the new cluster, and their putative functions in the sulfonation and epimerization of MM 4550 are proposed. Gene inactivation showed that, in addition to cmmI, two new genes, cmm22 and ‐23, encode a two‐component response system thought to regulate the production of MM 4550. Overexpression of cmmI, cmm22 and cmm23 promoted MM 4550 production in an engineered strain. Finally, the involvement and putative roles of all genes in the MM 4550 cluster are proposed based on the results of bioinformatics analysis, gene inactivation, and analysis of disruption mutants. Overall, the differences between the thienamycin and MM 4550 gene clusters are reflected in characteristic structural elements and provide new insights into the biosynthesis of the complex carbapenems.     

Generation of linalool derivatives in an artificial honey produced from bees fed with linalool-enriched sugar syrup

This paper presents a novel procedure to investigate the bioconversion of nectar components via the ‘intermediate’ honeybee and under the effect of the conditions in the beehive. The procedure was applied with linalool, the major component in the extract of Citrus spp. flowers, in order to investigate its bioconversion to linalool derivatives, the major volatiles of citrus honey. Bees were fed daily with 1 L sugar syrup 1:1 (w/v) containing 1 mL of (±) linalool, while control bees were fed with the same amount of linalool-free syrup. The artificial honey was analysed by means of ultrasound-assisted extraction followed by GC–MS analysis. The results show that the formation of both furan and pyran linalool oxides as well as terpendiol I is favoured, probably catalysed by the enzymes secreted by the bee. On the contrary, important linalool derivatives of citrus honey such as lilac aldehydes, cis- and trans-dehydroxy linalool oxides (E)-2,6-dimethyl-6-hydroxy-2,7-octadienal and (Z)-8-hydroxylinalool were absent in the artificial honey, suggesting the requirement of a plant-derived enzyme for their bioconversion. The same stands for (E)-8-hydroxylinalool, major volatile of citrus honey, although small amounts were present in the artificial honey. From these results, it can be concluded that feeding honeybees with linalool-enriched sugar syrup is not an effective way to produce artificial citrus honey similar to the natural one.