Entity

Time filter

Source Type


Lopez-Nicolas J.M.,University of Murcia | Lopez-Nicolas J.M.,Murcia Biomedical Research Institute IMIB | Andreu-Sevilla A.J.,University Miguel Hernandez | Garcia-Carmona F.,University of Murcia | And 2 more authors.
Food Analytical Methods | Year: 2014

The combination headspace solid phase micro-extraction + gas chromatography-mass spectrometry + gas chromatography with flame ionization detector was successfully used in quantitative determination of the instrumental odor of pear juice. Esters, aldehydes, alcohols, and terpenes were the major chemical families of the pear juice odor. Twenty-six were identified and quantified, with propyl acetate, hexyl acetate, 2-methyl-1-butanol, and butyl acetate being the major compounds. α-Cyclodextrins (CD) significantly improved the color of pear juice, leading to higher values of L* and lower of scores of a*, b*, and ΔE*. However, α-CD also reduced the total concentration of volatiles in the headspace of the juice by creating inclusion complexes with volatiles; after 40 min of oxidation, total volatiles were 8.2 and 3.4 mg L-1 in control and α-CD-treated juices, respectively. But in summary, the global quality (joint consideration of the main sensory attributes) was improved by the addition of α-CD (6.9 compared to 5.2). © 2014 Springer Science+Business Media New York. Source


Orenes-Pinero E.,University of Murcia | Garcia-Carmona F.,University of Murcia | Garcia-Carmona F.,Murcia Biomedical Research Institute IMIB | Sanchez-Ferrer A.,University of Murcia | Sanchez-Ferrer A.,Murcia Biomedical Research Institute IMIB
Food Chemistry | Year: 2013

Phenol hydroxylase gene cloning from the thermophilic bacteria Geobacillus thermoglucosidasius was used to develop an effective method to convert tyrosol into the high-added-value compound hydroxytyrosol by hydroxylation. Phenol hydroxylase is a two-component enzyme encoded by pheA1 and pheA2 genes and strictly dependent on NADH and FAD. These two genes were subcloned together as a 2 kb fragment into Escherichia coli Rosetta cells, and the transformants were able to grow and effectively transform up to 5 mM of phenol and tyrosol using IPTG (isopropyl-β-d-thiogalactopyranoside) as inducer. In addition, when a new fragment with a 340 pb upstream pheA1 gene was subcloned, a similar biotransformation rate was attained without IPTG, confirming that this fragment encodes for a phenol hydroxylase promoter that can be recognised by E. coli. Both transformants brought about the total bioconversion of monophenols at a high concentration (5 mM), which represents an increase, both in concentration and in yield, compared with that previously described in the bibliography. The use of the transformant with its constitutive promoter was more interesting from a biotechnological point of view, since it is not necessary to use IPTG. It also gave rise to greater operational stability. © 2013 Elsevier Ltd. All rights reserved. Source


Vidal P.J.,University of Murcia | Lopez-Nicolas J.M.,University of Murcia | Lopez-Nicolas J.M.,Murcia Biomedical Research Institute IMIB | Gandia-Herrero F.,University of Murcia | And 3 more authors.
Food Chemistry | Year: 2014

Betalains are natural pigments characteristic of plants of the order Caryophyllales. In this work, the role of betalains in the anti-inflammatory activity described for plant extracts is analysed in terms of the inactivation of the enzymes involved in the biochemical response (lipoxygenase and cyclooxygenase). Pure natural betalains and semi-synthetic analogues are demonstrated to promote a significant reduction of the enzymes activity. Reactions were followed spectrophotometrically and by HPLC-DAD. Phenethylamine-betaxanthin was the most potent in the inactivation of cyclooxygenase, with a reduction of 32% of the control activity at 125 μM, while the natural pigment betanidin and a betalain analogue derived from indoline resulted as the most potent inactivators of lipoxygenase, with IC 50 values of 41.4 and 40.1 μM, respectively. Molecular docking studies revealed that betalains interact with the lipoxygenase amino acids involved in substrate binding and with Tyr-385 and Ser-530 close to the cyclooxygenase active site, interfering in enzyme catalysis. © 2014 Elsevier Ltd. All rights reserved. Source


Sanchez-Carron G.,University of Murcia | Garcia-Garcia M.I.,University of Murcia | Garcia-Garcia M.I.,Murcia Biomedical Research Institute IMIB | Zapata-Perez R.,University of Murcia | And 5 more authors.
PLoS ONE | Year: 2013

Nicotinamidases catalyze the hydrolysis of nicotinamide to nicotinic acid and ammonia, an important reaction in the NAD+ salvage pathway. This paper reports a new nicotinamidase from the deep-sea extremely halotolerant and alkaliphilic Oceanobacillus iheyensis HTE831 (OiNIC). The enzyme was active towards nicotinamide and several analogues, including the prodrug pyrazinamide. The enzyme was more nicotinamidase (kcat/Km = 43.5 mM-1s-1) than pyrazinamidase (kcat/Km = 3.2 mM-1s-1). Mutational analysis was carried out on seven critical amino acids, confirming for the first time the importance of Cys133 and Phe68 residues for increasing pyrazinamidase activity 2.9- and 2.5-fold, respectively. In addition, the change in the fourth residue involved in the ion metal binding (Glu65) was detrimental to pyrazinamidase activity, decreasing it 6-fold. This residue was also involved in a new distinct structural motif DAHXXXDXXHPE described in this paper for Firmicutes nicotinamidases. Phylogenetic analysis revealed that OiNIC is the first nicotinamidase described for the order Bacillales. © 2013 Sánchez-Carrón et al. Source


Garcia-Garcia M.I.,University of Murcia | Garcia-Garcia M.I.,Murcia Biomedical Research Institute IMIB | Hernandez-Garcia S.,University of Murcia | Sanchez-Ferrer A.,University of Murcia | And 3 more authors.
Journal of Agricultural and Food Chemistry | Year: 2013

Red Globe grape polyphenol oxidase, partially purified using phase partitioning with Triton-X114, was used to study the oxidation of hydroxytytosol (HT) and its related compounds tyrosol (TS), tyrosol acetate (TSA), and hydroxytyrosol acetate (HTA). The enzyme showed activity toward both monophenols (monophenolase activity) and o-diphenols (diphenolase activity) with a pH optimum (pH 6.5) that was independent of the phenol used. However, the optimal temperature for diphenolase activity was substrate-dependent, with a broad optimum of 25-65 C for HT, compared with the maximum obtained for HTA (40 C). Monophenolase activity showed the typical lag period, which was modulated by pH, substrate and enzyme concentrations, and the presence of catalytic amounts of o-diphenols. When the catalytic power (Vmax/KM) was determined for both activities, higher values were observed for o-diphenols than for monophenols: 9-fold higher for the HT/TS pair and 4-fold higher for HTA/TSA pair. Surprisingly, this ratio was equally higher for TSA (2.2-fold) compared with that of TS, whereas no such effect was observed for o-diphenols. This higher efficiency of TSA could be related to its greater hydrophobicity. Acetyl modification of these phenols not only changes the kinetic parameters of the enzyme but also affects their antioxidant activity (ORAC-FL assays), which is lower in HTA than in HT. © 2013 American Chemical Society. Source

Discover hidden collaborations