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Biomedical subjects

A Arnoldi

Publications and source records attributed to A Arnoldi.

18 recordsLinked to original sources
PubMed2003

Lysinoalanine content of formulas for enteral nutrition.

Casein and caseinates are the main ingredients of formulas for enteral nutrition. Their manufacturing procedure and the thermal treatments necessary to assure microbiological stabilization and satisfactory shelf-life of the end-products are particularly favorable for the formation of lysinoalanine (LAL), a cross-linked amino acid that is considered a useful marker of the thermal damage and reduced digestibility of proteins. The lysinoalanine content of 18 different kinds of formulas for enteral nutrition was determined by HPLC after derivatization. The liquid formulas have an average value of 528 microg/g protein LAL, ranging from 160 to 800 microg/g protein (average content of formulas for pediatric use 747 microg/g protein). These values are rather high considering that the average value detected in UHT-treated drinkable milk is 117 microg/g protein. In principle, the preparation of caseinates and the thermal stabilization of the end products are the two steps more favorable for the formation of LAL. The fact that the five samples stabilized by an UHT-treatment have an average value of 512 microg/g protein suggests that the LAL content depends more on the quality of the starting ingredients than on the sterilization process. A better selection of the starting ingredients should improve the quality of formulas for enteral nutrition, which is very desirable when formulating foods for consumers with very high nutritional demands.

Caseins↗
PubMed2001

Effects of olive, canola, and sunflower oils on the formation of volatiles from the Maillard reaction of lysine with xylose and glucose.

Some important edible oils (extra virgin olive oil, canola oil, and sunflower oil) were added to aqueous glucose-lysine or xylose-lysine model systems to investigate their effect on the formation of volatiles from the Maillard reaction (MR). The volatile compounds were extracted by a Likens-Nickerson apparatus and quantified. Pyrazines, Maillard reaction products with an important impact on food flavor, appeared to be particularly sensitive to the presence of the oils in both the xylose-lysine and glucose-lysine model systems. The unsubstituted pyrazine was formed more with olive oil, less with canola oil, and even less with sunflower oil, whereas 2-methylpyrazine, 2,5-methylpyrazine, and 2,3-dimethylpyrazine were formed less with olive oil, more with canola oil, and even more with sunflower. The oxidative states of the oils and their fatty acid fingerprints were determined: the results indicated that the relative amounts of the pyrazines are sensitive to the degree of unsaturation of the oil. The autoxidation of the volatile compounds generated from the MR, investigated by the addition of free radical modulators (antioxidants alpha-tocopherol, 2,6-di-tert-butyl-4-methylphenol, and rosemary extract; or pro-oxidant alpha,alpha'-azobis-isobutyronitrile, a free radical initiator), was limited in respect to aqueous model systems.

Fatty Acids↗
PubMed2000

Autoxidation in xylose/lysine model systems.

The volatiles produced in xylose/lysine model systems added with an antioxidant (alpha-tocopherol, 2,6-di-tert-butyl-4-methylphenol, or rosemary extract) or a free radical initiator (alpha, alpha'-azobis(isobutyronitrile), AIBN) were analyzed to investigate the effects of the presence of free radicals on the Maillard reaction. The pH was maintained constant at 4 or 6, by adding a base, and the data were compared by principal component analysis (PCA). The additives were more effective at pH 4 than pH 6. At pH 4, the model system added with AIBN is very well-discriminated by PCA from the models with the antioxidants and the reference model system, indicating that the volatiles are sensitive to compounds that can interfere in an opposite way with free radical formation.

Free Radicals↗
PubMed2000

Synthesis, fungicidal activity, and QSAR of a series of 2-dichlorophenyl-3-triazolylpropyl ethers.

A series of new alkyl and arylalkyl ethers of 2-(2, 4-dichlorophenyl)-3-(1H-1,2,4-triazol-1-yl)propanol, related to the fungicide tetraconazole, were synthesized and tested in vitro or in vivo against seven common pathogens in comparison with tetraconazole. In vitro, most of them exhibited a broad spectrum of activity and an efficacy of the same order of magnitude of the standard, but the activity was influenced by the nature of the substituents. A QSAR study showed that lipophilicity is a major positive parameter in affecting the activity; the second relevant parameter is mu, whereas geometrical descriptors indicate that linear and narrow substituents are more suitable than wide ones. In in vivo assays some compounds had good activity on bean rust, either protective or curative. Sterol analysis showed that the mechanism of action is due to inhibition of 14alpha-demethylase.

Fungi↗
PubMed2000

Soy protein peptides regulate cholesterol homeostasis in Hep G2 cells.

The activation of LDL receptors was described recently in a human hepatoma cell line (Hep G2) exposed both to alpha + alpha' subunits from 7S soy globulin and to Croksoy(R)70, a commercial isoflavone-poor soy concentrate. To assess the final identity of the peptide(s) putatively responsible for the biochemical effect, experiments were performed in Hep G2 cells, exposed either to synthetic peptides corresponding to specific sequences of 7S soy globulin or to peptides from the in vitro digestion of Croksoy(R)70. Moreover, the ability of the whole 7S globulin, its subunits and whole Croksoy(R)70 to interfere in the apolipoprotein B (apo B) secretion in the medium as well as in sterol biosynthesis was evaluated in the same model. Increased (125)I-LDL uptake and degradation vs. controls were shown after Hep G2 incubation with a synthetic peptide (10(-)(4) mol/L, MW 2271 Da) corresponding to positions 127-150 of the 7S globulin. Cells exposed to Croksoy(R)70 enzyme digestion products showed a more marked up-regulation of LDL receptors vs. controls, compared with vs. Hep G2 cells incubated with undigested Croksoy(R)70. Among soy-derived products, only the 7S globulin inhibited apo B secretion and (14)C-acetate incorporation when tested in Hep G2 cells at a concentration of 1.0 g/L. These findings support the hypothesis that if one or more peptides can reach the liver after intestinal digestion, they may elicit a cholesterol-lowering effect. Moreover, the protein moiety, devoid of isoflavone components, is likely to be responsible for this major biochemical effect of soy protein.

Amino Acid Sequence↗
PubMed1999

Optimization of the synthesis of the cross-linked amino acid ornithinoalanine and nuclear magnetic resonance characterization of lysinoalanine and ornithinoalanine.

Lysinoalanine (LAL) and ornithinoalanine (OAL) are unnatural amino acids that can be formed in food submitted to thermal treatment, especially in alkaline conditions. The paper presents an optimization of the synthetic procedure for the preparation of a standard of OAL that could be very useful to study the toxicological and nutritional consequences of the presence of OAL in food. In the meantime, it was possible to develop a method based on nuclear magnetic resonance for the diastereomeric characterization of LAL and OAL without derivatization. Interest in this method is based on the known differences in the nephrotoxicity of the two diastereisomers of LAL.

Alanine↗
PubMed1999

Reinvestigation of the reaction between 2-furancarboxaldehyde and 4-hydroxy-5-methyl-3(2H)-furanone.

The reaction between 2-furancarboxaldehyde and 4-hydroxy-5-methyl-3(2H)-furanone was reinvestigated as a part of a systematic study on low molecular weight colored compounds from the Maillard reaction. In acetic acid/piperidine, besides 2-(2-furanylmethylene)-4-hydroxy-5-methyl-3(2H)-furanone (1) and 5-[2-(2-furanyl)ethenyl]-2-(2-furanylmethylene)-4-hydroxy-5-methyl -3( 2H)-furanone (2), four novel compounds, 15a, 15b, 16a, and 16b, were isolated and characterized. These compounds are produced from two molecules of furanone 1 and one molecule of 2-furancarboxaldehyde, and a mechanism is proposed for their formation. Compounds 1, 15a, 15b, 16a, and 16b are formed also by reacting 2-furancarboxaldehyde and 4-hydroxy-5-methyl-3(2H)-furanone in water at pH 3 and 2, whereas 2 was never detected. The formation of these compounds was studied also in xylose/lysine and xylose/glycine model systems.

Chromatography, High Pressure Liquid↗
PubMed1998

Formation of N-Nitrosoterbuthylazine and N-Nitrosoterbutryn in a Model System of Soil Water.

The s-triazines terbutryn and terbuthylazine are currently used in Italy for weed control. A possible reaction of these compounds in the environment is N-nitrosation. Experiments performed in 10 mM CaCl(2) as a model of soil water indicated that N-nitrosation is favored only at low pH values and that the N-nitroso derivatives are fairly stable. In the presence of soil either parent compounds or N-nitroso derivatives are strongly adsorbed. These results seem to indicate that the possibility of formation of N-nitrosoterbuthylazine and N-nitrosoterbutryn in common agricultural soil is very remote.

Journal Article↗
PubMed1994

Studies on azole-induced cell death in Saccharomyces cerevisiae.

The Saccharomyces cerevisiae strain XL16-5B exhibited a fungicidal response to treatment with ketoconazole. Cell death became apparent during prolonged treatment over 72 h following an initial period over 24 h where viable cells were found and limited cell division occurred. Sterol analysis showed some differences between XL16-5B and the strain XY729-5a, which had a fungistatic response to ketoconazole. In particular, the level of ergosterol was higher in XL16-5B and remained high during treatment.

Cytochrome P-450 Enzyme System↗
PubMed1990

Synthesis and anticonvulsant and sedative-hypnotic activity of 4-(alkylimino)-2,3-dihydro-4H-1-benzopyrans and -benzothiopyrans.

A series of 4-(alkylimino)-5-hydroxy-7-alkyl-2,3-dihydro-4H-1-benzopyrans and -thiopyrans were synthesized and evaluated for anticonvulsant activity. Preliminary screening of these compounds revealed that 2,2-dimethyl-4-[(2-hydroxyalkyl)imino]-5-hydroxy-7-pentyl-2,3- dihydro-4H-1-benzopyrans 19 and 29, the 7-butyl analogue 34, and the corresponding 7-pentyl-4H-1-benzothiopyrans 38 and 39 had the most promising anticonvulsant activity. Synthesis of both enantiomers of 29 and 39 indicated that the R isomers 30 and 40 were the most active and showed very good protection against MES, pentylenetetrazole, and mercaptopropionic acid induced seizures after oral administration in mice. In the Irwin test these compounds showed a generalized depressant activity but at dosages higher than those showing anticonvulsant activity, whereas acute toxicity after oral administration was low (LD50 higher than 400 mg/kg).

Animals↗
PubMed1986

Pyrethroid metabolism: studies on cis- and trans-phenothrins, and related epoxide intermediates.

Two synthetic pyrethroids, cis- and trans-phenothrins, undergo an environmental degradation which involves extensive photooxidation on their acidic residue, which contains a double bond. It has been shown that the metabolism of these compounds occurs via epoxidation of the isobutenyl side-chain also with hepatic microsomal preparations. The results did not indicate any formation of epoxide intermediates on the isobutenyl side-chain. Further evidence that metabolism of cis- and trans-phenothrins does not occur via an epoxide intermediate is furnished by the fact that in vitro activity of hepatic microsomal epoxide hydrolase remained unaffected. These findings may be related to the unfavorable steric hindrance of the tri-substituted double bond on the acidic moiety of these pyrethroids.

Animals↗
PubMed1986

Stereochemical considerations on the inhibition of hepatic epoxide hydrolase by some pesticides and their epoxides.

The present studies identify the steric factors involved in the hydration of epoxide intermediates of some pesticides by hepatic epoxide hydrolase. Investigations were carried out regarding the formation of reactive epoxide intermediates and their different interactions with the hepatic epoxide hydrolase. Some pesticides and their parent epoxides were selected on the basis of the steric hindrance on the oxirane ring. The results indicate that the inhibition of this enzyme depends on the steric hindrance produced by substituents on the oxirane ring of these pesticides. Mono- and di-substituted oxiranes are good substrates of the epoxide hydrolase and non-competitive inhibitors of the hydration of styrene oxide, while tri-substituted epoxides are virtually inactive on inhibiting the hepatic epoxide hydrolase activity.

Animals↗
PubMed1983

Effect of diastereoisomeric epoxyrotenones on hepatic epoxide hydrase activity.

The effect on epoxide hydrase activity of the two diastereomeric (6'R) and (6'S)-6',7'-epoxyrotenones formed during the oxidative metabolism of rotenone on the isopropenyl side chain is reported. The activity of microsomal epoxide hydrase was determined using styrene oxide as substrate. The results indicate that the two diastereomeric 6',7'-epoxyrotenones are good substrates for epoxide hydrase and are noncompetitive inhibitors for the hydration of styrene oxide. The more polar of the two isomers is more active as inhibitor of this enzyme.

Animals↗