Gianna Allegrone

Amedeo Avogadro University of Eastern Piedmont, Alessandria, Piedmont, Italy

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Publications (24)46.67 Total impact

  • [show abstract] [hide abstract]
    ABSTRACT: Haemophilus influenzae is a major pathogen of the respiratory tract in humans that has developed the capability to exploit host NAD(P) for its nicotinamide dinucleotide requirement. This strategy is organized around a periplasmic enzyme termed NadN (NAD nucleotidase), which plays a central role by degrading NAD into adenosine and NR (nicotinamide riboside), the latter being subsequently internalized by a specific permease. We performed a biochemical and structural investigation on H. influenzae NadN which determined that the enzyme is a Zn2+-dependent 5'-nucleotidase also endowed with NAD(P) pyrophosphatase activity. A 1.3 Å resolution structural analysis revealed a remarkable conformational change that occurs during catalysis between the open and closed forms of the enzyme. NadN showed a broad substrate specificity, recognizing either mono- or di-nucleotide nicotinamides and different adenosine phosphates with a maximal activity on 5'-adenosine monophosphate. Sequence and structural analysis of H. influenzae NadN led us to discover that human CD73 is capable of processing both NAD and NMN, therefore disclosing a possible novel function of human CD73 in systemic NAD metabolism. Our data may prove to be useful for inhibitor design and disclosed unanticipated fascinating evolutionary relationships.
    Biochemical Journal 09/2011; 441(1):131-41. · 4.65 Impact Factor
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    ABSTRACT: Lipopeptide biosurfactants produced by the Bacillus licheniformis V9T14 strain showed an interesting anti-adhesion activity against biofilm formation of human pathogenic bacterial strains. The chemical characterisation of the crude extract of V9T14 strain was first developed through electrospray ionisation mass spectrometry (ESI-MS) and ESI-MS/MS direct infusions: two sets of molecular ion species belonging to the fengycin and surfactin families were revealed and their structures defined, interpreting their product ion spectra. The LC/ESI-MS analysis of the crude extract allowed to separate in different chromatogram ranges the homologues and the isoforms of the two lipopeptide families. The extract was then fractionated by silica gel chromatography in two main fractions, I and II. The purified biosurfactants were analysed through a new, rapid and suitable LC/ESI-MS/MS method, which allowed characterising the composition and the structures of the produced lipopeptides. LC/ESI-MS/MS analysis of fraction I showed the presence of C(13), C(14) and C(15) surfactin homologues, whose structures were confirmed by the product ion spectra of the sodiated molecules [M + Na](+) at m/z 1030, 1044 and 1058. LC/ESI-MS/MS analysis of fraction II confirmed the presence of two main fengycin isoforms, with the protonated molecules [M + H](+) at m/z 1478 and 1506 corresponding to C(17) fengycin A and C(17) fengycin B, respectively. Other homologues (C(14) to C(16)) were revealed and confirmed as belonging to fengycin A or B according to the retention times and the product ions generated, although with the same nominal mass. Finally, a relative percentage content of each homologue for both lipopeptides families in the whole extract was proposed.
    Biological Mass Spectrometry 07/2010; 45(7):772-8. · 3.41 Impact Factor
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    ABSTRACT: Orange (Citrus sinensis L.) juice comprises a complex mixture of volatile components that are difficult to identify and quantify. Classification and discrimination of the varieties on the basis of the volatile composition could help to guarantee the quality of a juice and to detect possible adulteration of the product. To provide information on the amounts of volatile constituents in fresh-squeezed juices from four orange cultivars and to establish suitable discrimination rules to differentiate orange juices using new chemometric approaches. Fresh juices of four orange cultivars were analysed by headspace solid-phase microextraction (HS-SPME) coupled with GC-MS. Principal component analysis, linear discriminant analysis and heuristic methods, such as neural networks, allowed clustering of the data from HS-SPME analysis while genetic algorithms addressed the problem of data reduction. To check the quality of the results the chemometric techniques were also evaluated on a sample. Thirty volatile compounds were identified by HS-SPME and GC-MS analyses and their relative amounts calculated. Differences in composition of orange juice volatile components were observed. The chosen orange cultivars could be discriminated using neural networks, genetic relocation algorithms and linear discriminant analysis. Genetic algorithms applied to the data were also able to detect the most significant compounds. SPME is a useful technique to investigate orange juice volatile composition and a flexible chemometric approach is able to correctly separate the juices.
    Phytochemical Analysis 07/2009; 20(5):402-7. · 2.48 Impact Factor
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    ABSTRACT: In this work, two biosurfactant-producing strains, Bacillus subtilis and Bacillus licheniformis, have been characterized. Both strains were able to grow at high salinity conditions and produce biosurfactants up to 10% NaCl. Both extracted-enriched biosurfactants showed good surface tension reduction of water, from 72 to 26-30 mN/m, low critical micelle concentration, and high resistance to pH and salinity. The potential of the two lipopeptide biosurfactants at inhibiting biofilm adhesion of pathogenic bacteria was demonstrated by using the MBEC device. The two biosurfactants showed interesting specific anti-adhesion activity being able to inhibit selectively biofilm formation of two pathogenic strains. In particular, Escherichia coli CFT073 and Staphylococcus aureus ATCC 29213 biofilm formation was decreased of 97% and 90%, respectively. The V9T14 biosurfactant active on the Gram-negative strain was ineffective against the Gram-positive and the opposite for the V19T21. This activity was observed either by coating the polystyrene surface or by adding the biosurfactant to the inoculum. Two fractions from each purified biosurfactant, obtained by flash chromatography, fractions (I) and (II), showed that fraction (II), belonging to fengycin-like family, was responsible for the anti-adhesion activity against biofilm of both strains.
    Applied Microbiology and Biotechnology 05/2009; 83(3):541-53. · 3.69 Impact Factor
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    ABSTRACT: A simple and efficient method for the determination of isopropyl-9H-thioxanten-9-one (ITX) in different fat content milk samples and baby milk samples stored in packaged cartons was developed and validated. Samples were extracted using solid-phase extraction (SPE) and analysed by gas chromatography-tandem mass spectrometry operated in selected reaction monitoring mode (SRM). Validation was carried out in terms of limit of detection (LOD), limit of quantitation (LOQ), linearity, precision and trueness. LOD and LOQ values in the low microg/L were achieved, whereas linearity was established within 0.5-500 microg/L range. Good precision was obtained both in terms of intra-day repeatability and inter-day precision on two concentration levels (RSD% lower than 2%). Good percentage recoveries were obtained (92.0-102.0%) even in the presence of high amount of fat. Finally, the developed method was successfully applied to analyse a number of commercial milk samples with different fat content and baby milk samples.
    Journal of Chromatography 11/2008; 1214(1-2):128-33. · 4.61 Impact Factor
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    ABSTRACT: A stability indicating high performance liquid chromatography procedure has been developed for the simultaneous determination of guaifenesin (GUA), methyl p-hydroxybenzoate (MHB) and propyl p-hydroxybenzoate (PHB) in a commercial cough syrup dosage form. The method was specific and stability indicating as chromatographic conditions were selected to provide adequate separation of GUA, MHB and PHB from the putative degradation products guaiacol (GUAI) and p-hydroxybenzoic acid (HBA) as well as from excipients. The isocratic separation and quantitation were achieved within 17 min on a 150-mm column with an ether-linked phenyl stationary phase and a hydrophilic endcapping. The mobile phase was constituted of eluant A: aqueous phosphate buffer (pH 3.0, 10 mM)/acetonitrile 25/75 (v/v) and eluant B:methanol; the A:B ratio was 85:15 (v/v) with a flow rate 1 ml min-1 and detection of analytes at 254 and 276 nm. The method showed good linearity for the GUA-MHB-PHB mixture in the 95-285, 4-12, and 1-3 microg ml-1 ranges, respectively, being all the square of the correlation coefficients greater than 0.999. The interday R.S.D.s were 1.17, 1.14, and 0.91%, for GUA, MHB, and PHP, respectively. The method demonstrated also to be accurate; indeed the average recoveries, at 100% of the target assay concentration, were 100.5, 100.3, and 100.7% with relative standard deviations of 0.8, 0.7, and 0.4% for GUA, MHB, and PHB, respectively, from laboratory prepared samples. The applicability of the method was evaluated in commercial dosage form analysis as well as in stability studies.
    Journal of Pharmaceutical and Biomedical Analysis 07/2006; 41(3):798-803. · 2.95 Impact Factor
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    ABSTRACT: The chiral differentiation of the enantiomers of 2-methylbutanoic acid, 2-methylpentanoic acid and 2-methylhexanoic acid was achieved by diastereomeric derivatization with (R)-( – )-pantolactone. GC separation on achiral DB-1, DB-1701 and DB-WAX capillary columns as well as 1H- and 13C-NMR enantiodiscrimination were obtained, affording good resolution and quantitative evaluation of enantiomer composition. The method applied to 2-methylbutanoic acid present in the aromatic fraction extracted from cultivated strawberry (Fragaria vesca) indicated a high enantiomeric excess of the (S)-isomer.
    Flavour and Fragrance Journal 04/2006; 7(3):163 - 167. · 1.82 Impact Factor
  • Gianna Allegrone, Massimo Barbeni
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    ABSTRACT: The volatile components of caja fruit (Spondias lutea L.) were characterized using two different methods of isolation: (a) steam distillation followed by extraction with dichloromethane; (b) direct extraction of caja pulp with diethyl ether. Fractionation of the flavour concentrates on silica gel was accomplished. The extracts were analysed by dual capillary gas chromatography and combined capillary GC-MS. About 100 flavour compounds were identified for the first time as Spondias lutea volatiles. Among them butanoic acid, ethyl 3-hydroxyhexanoate, butanol, ethyl 3-hydroxybutanoate, butyl butanoate and butyl 3-hydroxybutanoate were the most abundant constituents. The chiral distribution of the main 3-hydroxy aliphatic esters was evaluated by derivatization with (S)-tetrahydro-5-oxo-2-furancarbonyl chloride (TOF). GC separation on an achiral DB-1 column afforded good resolution of the diastereoisomers and indicated an enantiomeric excess of the (R)-isomers.
    Flavour and Fragrance Journal 04/2006; 7(6):337 - 342. · 1.82 Impact Factor
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    Gianna Allegrone, Flavio Belliardo, Paolo Cabella
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    ABSTRACT: Fresh juices of four Italian cultivars of lemons (Citrus limon Burm) have been analyzed by headspace solid phase microextraction coupled to gas chromatography and gas chromatography-mass spectrometry (GC-MS). The best results have been obtained with the 2 cm 50/30 microm divinylbenzene/carboxen on poly(dimethylsiloxane) fiber, using a homogenization time of 1 h at 40 degrees C and a sampling period of 30 min. A total of 35 volatile compounds have been identified by GC-MS, and their relative amounts have been calculated by adding internal standard to the samples. Differences in composition of lemon juices volatile components have been observed. Verdello Siracusano lemon juice has the highest amount of volatile compounds (50.28 mg/L), followed by Interdonato (8.39 mg/L), Primo Fiore Capo d'Orlando (5.75 mg/L), and Femminello Siracusano (2.62 mg/L) juices. Volatile compounds mainly consist of mono- and sesquiterpene hydrocarbons and oxygenated molecules (aldheydes, monoterpene alcohols, and monoterpene esters). Headspace solid phase microextraction coupled to a gas chromatograph equipped with a specific sulfur detector, a sulfur chemiluminescence detector, let us detect and quantify dimethyl sulfide compound at the microgram/liter level in lemon juices.
    Journal of Agricultural and Food Chemistry 04/2006; 54(5):1844-8. · 2.91 Impact Factor
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    ABSTRACT: A series of chimeric compounds bearing the combretastatin and the nitrogen mustard cores were synthesized. All the compounds were cytotoxic and inhibited tubulin polymerization. When combretastatin was joined to chlorambucil via an ester linkage, the resultant compound proved to be significantly more potent than the two compounds put together. When combretastatin was joined to nitrogen mustard via an ether linkage or when a true hybrid was synthesized, loss of potency was observed. Nonetheless, these latter compounds appeared to be more efficacious and surprisingly were able to inhibit tubulin depolymerization at high concentrations.
    Bioorganic & Medicinal Chemistry Letters 09/2005; 15(15):3551-4. · 2.34 Impact Factor
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    ABSTRACT: The structure of an impurity contained in samples of all trans-retinoic acid was established by means of NMR and MS spectra, and confirmed by X-ray diffraction analysis. The chemical structure of the impurity 2 was found to be strictly correlated to the synthetic procedure employed for the preparation of the retinoic acid samples. Single crystal analysis allowed us to characterise the molecular conformation and the crystal structure of 2.
    Bioorganic & Medicinal Chemistry Letters 09/2005; 15(15):3528-31. · 2.34 Impact Factor
  • Giorgio Grosa, Gianna Allegrone, Erika Del Grosso
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    ABSTRACT: A liquid chromatography-mass spectrometry (LC-MS) method was developed for the characterization of strophanthin-K, a mixture of cardiac glycosides extracted from the seeds of Strophanthus kombe. The method is based on the separation of the cardenolides using high performance liquid chromatography (HPLC) followed by detection with electrospray ionization mass-spectrometry (ESI-MS). Chromatographic separation of the analytes was achieved on a RP C-18 column using water: 1% formic acid in water (v/v):acetonitrile gradient mobile phase. Strophanthin-K glycosides studied in ESI-MS in negative ion mode formed abundant adduct ions [M+HCOO](-) while the pseudomolecular ions [M-H](-) are obtained in ESI-MS/MS experiments. Six different cardiac glycosides were identified and characterized: k-strophanthoside, k-strophanthin-beta, helveticoside (erysimin), erysimoside, cymarin and neoglucoerysimoside. Forced degradation investigations done with strophanthin-K showed that k-strophanthidin (the aglycone of strophanthin-K glycosides) was the main product of degradation in acidic conditions; however, in basic conditions, the hydrolysis of the unsaturated 17beta-lactones to the corresponding gamma-hydroxy acids was the predominant degradation pathway.
    Journal of Pharmaceutical and Biomedical Analysis 07/2005; 38(1):79-86. · 2.95 Impact Factor
  • Journal of Organic Chemistry - J ORG CHEM. 04/2002; 56(18).
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    ABSTRACT: -nonanolide in the (R) enantiomeric form is obtained, close to (R) -decanolide, as major transformation product of (R) coriolic acid in Pichia stipitis; feeding experiments of the (S) enantiomer lead to -decanolide as major metabolite
    Biotechnology Letters 01/1994; 16(9):935-938. · 1.85 Impact Factor
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    ABSTRACT: The biogeneration of (R) Z-7-decen-4-olide (γ-jasmolactone) (6) in Phichia stipitis and ohmeri from one of the products derived from linolenic acid via photooxidation/reduction is reported
    Bioorganic & Medicinal Chemistry Letters. 12/1993; 3(12):2777–2780.
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    ABSTRACT: Baker's yeast reduction of lactones8,a-d proceeds under kinetic resolution to give (S)11,a-d of low ee values, increasing with the length of the side chain, occurring the double bond saturation in anti fashion on the beta re face, as indicated by the obtainment from4 and6 of5 and7, respectively.
    Tetrahedron Letters - TETRAHEDRON LETT. 01/1993; 34(40):6467-6470.
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    ABSTRACT: In growing cultures of Cladosporium suaveolens (R) coriolic acid (3) is converted into 5-decanolide enriched in the (S) enantiomer (2) (ca. 0.4 ee), while recovered coriolic acid shows the same enantiomeric composition of the precursor, as indicated by NMR studies onto a set of (+)-MTPA derivatives.
    Biotechnology Letters 01/1993; 15(12):1233-1236. · 1.85 Impact Factor
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    ABSTRACT: Summary Degradation of the C-16 and C-18 racemic hydroxy acids 1–4 to C-10 and C-12 ?-lactones 5–8 proceeds inYarrowia lipolytica andPichia ohmeri with opposite stereochemistry
    Biotechnology Letters 01/1992; 14(8):665-668. · 1.85 Impact Factor
  • ChemInform 01/1992; 23(10):73-73.
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    ABSTRACT: (Z6)-gamma-dodecenolactone samples produced endogenously inFusarium poae and biogenerated from (10R, S) 10-hydroxy-octadeca-(E8, Z12)-dienoic acid inCladosporium suaveolens show (R) and (S) configurations, respectively.
    Biotechnology Letters 10/1991; 13(11):765-768. · 1.85 Impact Factor