An improved method for determination of the activity of β-galactosidase in yoghurt by high-performance liquid chromatography

Summary A new method has been developed for the HPLC determination of the activity of lactase from the microorganisms in yoghurt. The method is based upon the ability of -galactosidase to hydrolyze lactose bonds in glucose and galactose. To determine such activity in yoghurt, 1 mL of yoghurt was diluted 110 with 0.1 M phosphate buffer (pH 7) containing 2 % (w/v) lactose and 5 mM dithioerythritol as reducing agent; the mixture was the incubated and injected into the HPLC. Lactase activity remained high as long as the number of viable microorganisms did not fall below the minimum CFU·mL^–1 (10⁷). This method is more repeatable than conventional colorimetric determination, and may also be automated for routine analysis.     

Production of β-carotene from beet molasses by Blakeslea trispora in stirred-tank and bubble column reactors

The effect of aeration rate and agitation speed on β-carotene production from molasses by Blakeslea trispora in a stirred-tank fermentor and optimization of the production of the pigment in a bubble column reactor were investigated. In addition, a central composite design was employed to determine the maximum β-carotene concentration at optimum values for the process variables (aeration rate, sugar concentration, linoleic acid, kerosene). By image analysis of the morphology of the fungus, a quantitative characterization of the hyphae and zygospores formed was obtained. The hyphae were differentiated to intacthyphae, vacuolated hyphae, evacuated cells and degenerated hyphae. An increased proportion of zygospores was correlated to high β-carotene production. In the stirred-tank fermentor, the highest concentration of the carotenoid pigment (92.0 mg/L) was obtained at an aeration rate of 1.5 vvm and agitation speed of 60 rpm. In the bubble column reactor, the aeration rate and concentration of sugars, linoleic acid, kerosene, and antioxidant significantly affected the production of β-carotene. In all cases, the fit of the model was found to be good. Aeration rate, sugar concentration, linoleic acid, and kerosene had a strong positive linear effect on β-carotene concentration. Moreover, the concentration of the pigment was significantly influenced by the negative quadratic effects of the given variables and by their positive or negative interactions. Maximum β-carotene concentration (360.2 mg/L) was obtained in culture grown in molasses solution containing 5% (w/v) sugar supplemented with linoleic acid (37.59 g/L), kerosene (39.11 g/L), and antioxidant (1.0 g/L).     

An improved procedure for the preparation of β-thiohydroximates for glucosinolate synthesis

A novel and simple method is described for the synthesis of β-thiohydroximates from oximes and 2,3,4,6-tetra-O-acetyl-1-thio-β-d-glucopyranose, which are key intermediates in the synthesis of glucosinolates. The procedure involves the in situ formation of an oximyl chloride from the oxime, using inexpensive bleach, which is then reacted directly under basic conditions with the thioglucopyranose.     

New apocarotenoids and β-carotene cleavage in Blakeslea trispora

Mixed cultures of strains of opposite sex ("mated" cultures) of Blakeslea trispora contain trisporic acids and other apocarotenoids, some of which mediate the sexual responses of this fungus and other Mucorales. In mated cultures of the wild-type strains F986 and F921 we identified eleven apocarotenoids: two C(18) trisporoids, three C(15) compounds with a monocyclofarnesane skeleton, a C(13) compound, and five C(7) compounds with a 2-methylhexane skeleton. Six of them are new natural products and two others are new for Blakeslea. Their structures were established by NMR and mass spectra and those of the C(7) and C(13) compounds were confirmed by chemical synthesis. The finding of these compounds and the presence of approximately equimolecular amounts of the C(18), C(15), and C(7) families led to the conclusion that β-carotene is initially split in three fragments by cleavage of its 13,14 and 11',12' double bonds.     

An improved method for preparing α,ω-dinitroalkanes

Summary We have suggested an improved method for preparing , -dinitroalkanes which consists in the action of silver nitrite on , -dibromoalkanes in petrofeum ether medium with heating.     

A simplified method for the HPLC resolution of α-carotene and β-carotene (trans and cis) isomers

A new HPLC/DAD (Diode Array Detector) method is proposed for the identification of some carotene isomers. The operating conditions adopted permit the resolution of alpha-carotene, all-trans-beta-carotene, 9-cis-beta-carotene, 13-cis-beta-carotene and 15-cis-beta-carotene. Moreover, the chromatographic conditions reported are simplified in respect of those reported up to now. The method is applied to the determination of carotenoids in a dried Dunaliella salina extract, but it could be also applied to other organic matrices such as eggs.     

A facile and efficient method for synthesis of β-iodocarboxylates from terminal epoxides

A facile and efficient method has been developed for synthesis of β-iodocarboxylates in the presences of Ph₃P/I₂. Starting from epoxides, a series of β-iodocarboxylate compounds can be directly obtained in toluene media with excellent yields. Moreover, the method was successfully applied for the late-stage modification of natural products, such as isosteviol and vincamine derivatives, achieving the corresponding β-iodocarboxylates in good yields.     

An improved method for the asymmetric protonation of enolates with chiral α-sulfinyl alcohols/trifluoroethanol

Enantioselective protonation of 2-methyl tetralone enolate using a stoichiometric amount of 2-sulfinyl alcohol (S,R_s)-1 as a chiral proton donor yields the corresponding chiral ketone with a high level of enantioselectivity, provided that the chiral proton donor (CPD) is regenerated with an achiral proton source (APS). In contrast, stereoselectivity was only moderate if catalytic CPD (0.2 equiv.) and an APS are used.     

New method for the synthesis of β-bromostyrenes

A new stereoselective method was developed for the synthesis of -bromostyrenes (E/Z > 5/1) starting from hydrazones of aromatic aldehydes and bromoform in the presence of CuCl.     

Valorization of raw materials from agricultural industry for astaxanthin and β-carotene production by Xanthophyllomyces dendrorhous

Waste deriving from food and agro-industries is a growing problem in our modern society. In order to reduce food waste and its associated impacts over the environment and public health, innovative strategies for the conversion of food wastes in added value products are studied. Whey is one of the prominent waste deriving from Sicilian diary industry. The growth and the carotenoid biosynthesis of the yeast Xanthophyllomyces dendrorhous by its cultivation in pre-treated whey were studied. The study showed the possibility of increasing the astaxanthin productivity from X. dendrorhous in a batch fermentative process under continuous illumination. Our work is focused on the importance of carotenogenesis by X. dendrorhous on whey for the economic and ecological aspect. The results obtained in the study provide useful information about the possible use of this waste material for carotenogenesis from X. dendrorhous.     

An improved procedure for the two carbon homologation of esters to α, β-unsaturated esters

Treatment of esters with diisobutylaluminum hydride (DIBAL) in the presence of lithio-trialkylphosphonoacetate results in improved yields of the homologated α, β-unsaturated esters. The problematic overreduction, which has previously observed in the half reduction of esters using DIBAL, is minimal (<3%) under these conditions.     

Electrochemical lithium extraction from β-lithium nitride

In this paper we report the electrochemical characterization of mixtures of ball-milled lithium nitride and iron metal. Several samples were prepared with different lithium nitride to iron molar ratios. X-ray diffraction (XRD) spectra showed the presence of iron metal in all the samples and β-lithium nitride in the samples with higher Li₃N/Fe ratio. No evidence of other phases was detected. The milled powders were used to prepare composite cathodes for the electrochemical characterization. It was found that lithium can be extracted from the materials at a flat potential of 1.2 V vs. Li. The sample with Li₃N/Fe molar ratio 8:1 showed the highest specific capacity (1125 mAh g⁻¹) corresponding to the extraction of 1.8 Li equivalents per mole of lithium nitride. Only a fraction of the lithium extracted was re-inserted in the following discharge cycle. A drastic reduction of the capacity was observed for all the samples on further cycling. An enhancement of the cyclability was obtained by lowering the end-charge voltage that resulted in a reduction of the lithium extracted. The lithium extraction/insertion process was characterized by a large voltage difference indicating that the reaction is largely irreversible.     

Solid-phase extraction and GC-MS analysis of potentially genotoxic cleavage products of β-carotene in primary cell cultures

A validated method for the simultaneous determination of prominent volatile cleavage products (CPs) of β-carotene in cell culture media has been developed. Target CPs comprised β-ionone (β-IO), cyclocitral (CC), dihydroactinidiolide (DHA), and 1,1,6-trimethyltetraline (TMT). CPs were extracted by solid-phase extraction applying a phenyl adsorbent, eluted with 10% (v/v) tetrahydrofuran in n-hexane, and identified and quantified by gas chromatography-mass spectrometry with electron impact ionization. Method validation addressed linearity confirmation over two application ranges and homoscedasticity testing. Recoveries from culture media were between 71.7% and 95.7% at 1.0 μg/ml. Precision of recoveries determined in intra-day (N = 5) and inter-day (N = 15) assays were <2.0% and <4.8%, respectively. Limit of detection and limit of quantification of the analysis method were <18.0 and <53.0 ng/ml for β-IO, CC, and TMT, whereas 156 and 474 ng/ml were determined for DHA, respectively. Although extractions of blank matrix proved the absence of interfering peaks, statistical comparison between slopes determined for instrumental and total method linearity revealed significant differences. The method was successfully applied in selecting an appropriate solvent for the fortification of culture media with volatile CPs, including the determination of their availability over the incubation period. For the first time, quantification of volatile CPs in treatment solutions and culture media for primary cells becomes accessible by this validated method.     

A new method for the synthesis of β-halonitroalkanes

Summary A new method is elaborated for the synthesis of -chloronitroalkanes; it consists in the reaction of phosphorus pentachloride with acetals obtained by the addition of primary -nitro alcohols to vinyl alkyl ethers.     

An improved high-performance liquid chromatographic method for simultaneous determination of tocopherols, tocotrienols and γ-oryzanol in rice

An improved normal phase high performance liquid chromatographic (NP-HPLC) method was developed for simultaneous quantification of eight vitamin E isomers (α-, β-, γ- and δ-tocopherols and α-, β-, γ- and δ-tocotrienols) and γ-oryzanol in rice. A complete separation of all compounds was achieved within 25 min using an Inertsil CN-3, SIL-100A 5 μM (4.6 mm × 250 mm) column and an isocratic elution system of hexane/isopropanol/ethylacetate/acetic acid (97.6:0.8:0.8:0.8, v/v/v/v) at a flow rate varying from 0.7 to 1.5 mL min(-1). A linear correlation coefficient (r(2)>0.99) and high reproducibility were obtained at concentrations ranging 0.05-10 μg mL(-1) for vitamin E isomers and 0.5-500 μg mL(-1) for γ-oryzanol. This method proved to be rapid, accurate and reproducible.     

An improved method for ratiometric fluorescence detection of pH and Cd using fluorescein isothiocyanate–quantum dots conjugates

In this study, thioglycolic acid capped-CdTe quantum dots (QDs) were modified by polyethylenimine (PEI), and then combined with fluorescein isothiocyanate (FITC) to fabricate FITC–CdTe conjugates. The self-assembly of FITC, CdTe and PEI was ascribed to electrostatic interactions in aqueous solution. The resulting conjugates were developed toward two routes. In route one, ratiometric photoluminescence (PL) intensity of conjugates (I_FITC/I_QDs) was almost linear toward pH from 5.3 to 8.7, and a ratiometric PL sensor of pH was favorable obtained. In route two, firstly added S²⁻ induced remarkable quenching of QDs PL peak (at the “OFF” state), which was restored due to following addition of Cd²⁺ (at the “ON” state). In the conjugates, successive introduction of S²⁻ and Cd²⁺ hardly influenced on FITC PL peaks. According to this PL “OFF-ON” mode, a ratiometric PL method for the detection of Cd²⁺ was achieved. Experimental results confirmed that the I_FITC/I_QDs exhibited near linear proportion toward Cd²⁺ concentration in the range from 0.1 to 15 μM, and the limit of detection was 12 nM. Interferential experiments adequately testified that the proposed sensors of pH and Cd²⁺ were practicable in real samples and complex systems. In comparison with conventional analytical techniques, the ratiometric PL method was simple, rapid, economic and highly selective.     

An improved procedure for the synthesis of 4-methylimidazol-2-one

A novel one-pot synthetic method of 4-methylimidazol-2-one is described. The target compound is conveniently synthesized from sodium diformylamide, a modified Gabriel reagent prepared, through condensation, hydrolyzation and cyclization reactions without separating intermediates, its total yield is 75.8%.     

An efficient method for the preparation of benzyl γ-ketohexanoates

Twenty acid chlorides, 4-(mono/di-benzyloxy)-4-ketobutanoyl chlorides (Ia–XXa) were synthesised by the reaction of monoesters of succinic acid with thionyl chloride. The product thus obtained (4-benzyloxy-4-ketobutanoyl chlorides) was treated with diethylcadmium to convert it into the corresponding keto-esters (Ib–XXb), the mono/di-benzyl-γ-ketohexanoates, with a good yield. All the compounds thus prepared were characterised by physical, spectroscopic (UV-VIS, IR, ¹H NMR, ¹³C NMR), and mass measurements techniques.     

Use of hydroxypropyl β-cyclodextrin hybrid monolithic material as adsorbent for dispersive solid-phase extraction of fluoroquinolones from environmental water samples

In this study, the hydroxypropyl β-cyclodextrin hybrid monolithic material was fabricated and firstly applied as an adsorbent for dispersive solid-phase extraction coupled with high-performance liquid chromatography to detect trace-level seven fluoroquinolones in water samples. The prepared hydroxypropyl β-cyclodextrin hybrid monolithic material was characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy, and adsorption experiments, which showed excellent specific adsorption to the target fluoroquinolones. Under the optimized conditions, the extraction methodology showed satisfactory precision with relative standard deviations between 2.6% and 5.6%, good linearity (R² ≥ 0.9990), and satisfactory recoveries (82.5–91.8%). The limits of detection and limits of quantification of the method were in the range of 0.4–1.2 and 1.4–4.0 ng/mL, respectively, which confirmed the possibility of quantifying trace levels. Furthermore, the material could be reused at least five times. These results demonstrated that the hydroxypropyl β-cyclodextrin hybrid monolithic material was a promising adsorbent for fluoroquinolones, and the established method combined dispersive solid-phase extraction with high-performance liquid chromatography was suitable for the determination of fluoroquinolones in aqueous samples.