221 research outputs found
Phenolic profile and antioxidative properties of the beefsteak fungus Fistulina hepatica
The phenolic composition of the edible beefsteak fungus Fistulina hepatica was determined by HPLC/DAD. The results showed a profile composed by caffeic, p-coumaric and ellagic acids, hyperoside and quercetin. Ellagic acid was the main compound in this species. Beefsteak fungus was also investigated for its capacity to act as a scavenger of DPPH radical and reactive oxygen species (superoxide radical, hydroxyl radical and hypochlorous acid). Good results were obtained against DPPH and superoxide radicals and hypochlorous acid but a prooxidant effect was observed for hydroxyl radical
Development and evaluation of an HPLC/DAD method for the analysis of phenolic compounds from olive fruits
A new HPLC/DAD methodology for separating nine phenolic compounds is described. This methodology is applied to the definition of qualitative and quantitative profiles of three Portuguese olive fruit cultivars (Cobrançosa, Madural and Verdeal). Two different extraction methods were needed for the complete definition of their profiles, one of them including a Sep-pack C18 cleaning step. The chromatographic separation was achieved using a Spherisorb ODS2 (25.0 × 0.46 cm; 5 μm, particle size) column. The solvent system used was a gradient of water-formic acid (19:1) and methanol, with a flow rate of 0.9 mL/min. The detection limit values for phenolic compounds were between 0.04 and 4.32 μg/mL and the method was precise. As a general rule, the recovery values were high. This technique can also be useful in the discrimination of Portuguese olive fruit cultivar
Phenolic profile of Cydonia oblonga Miller leaves
Cydonia oblonga Miller leaves phenolic compounds were analyzed by reversed-phase HPLC/DAD and HPLC/UV. Qualitative and quantitative analysis of phenolics were carried out in a total of 36
samples of quince leaves from three different geographical origins of Northern (Bragança and
Carrazeda de Ansiães) and Central Portugal (Covilhã) and three collection months (June, August,
and October of 2006). These leaves presented a common phenolic profile composed by nine
compounds: 3-O-, 4-O- and 5-O-caffeoylquinic acids, 3,5-O-dicaffeoylquinic acid, quercetin-3-Ogalactoside,
quercetin-3-O-rutinoside, kaempferol-3-O-glycoside, kaempferol-3-O-glucoside, and
kaempferol-3-O-rutinoside. 5-O-caffeoylquinic acid was the major phenolic compound (36.2%),
followed by quercetin 3-O-rutinoside (21.1%). Quince leaves are characterized by higher relative
contents of kaempferol derivatives than fruits (pulps, peels, and seeds), especially in what concerns
kaempferol-3-O-rutinoside (12.5%). C. oblonga leaves total phenolic content was very high, varying
from 4.9 to 16.5 g/kg dry matter (mean value of 10.3 g/kg dry matter), indicating that these leaves
can be used as a good and cheap source of bioactive constituents. Significantly differences were
observed in 3-O-caffeoylquinic and 3,5-O-dicaffeoylquinic acids contents, according to geographical
provenance and harvesting month, suggesting a possible use of these compounds as geographical
origin and/or maturity markers
Organic acids composition of Cydonia oblonga Miller leaf
Organic acid profiles of 36 Cydonia oblonga Miller leaf samples, from three different geographical origins of northern (Bragança and Carrazeda de Ansiães) and central Portugal (Covilhã), harvested in three collection months (June, August and October of 2006), were determined by HPLC/UV (214 nm). Quince leaves presented a common organic acid profile, composed of six constituents: oxalic, citric, malic, quinic, shikimic and fumaric acids. C. oblonga leaves total organic acid content varied from 1.6 to 25.8 g/kg dry matter (mean value of 10.5 g/kg dry matter). Quinic acid was the major compound (72.2%), followed by citric acid (13.6%).
Significant differences were found in malic and quinic acids relative abundances and total organic acid contents according to collection time, which indicates a possible use of these compounds as maturity markers.
Between June and August seems to be the best period to harvest quince leaves for preparation of decoctions or infusions, since organic acids total content is higher in this season
Effect of the conservation procedure on the contents of phenolic compounds and organic acids in Chanterelle (Cantharellus cibarius) Mushroom
To check the influence of the conservation procedure in the chemical composition of chanterelle mushroom, phenolic compounds and organic acids of samples preserved under four different
conditions (drying, freezing, conservation in olive oil and in vinegar) were determined. Phenolics and
organic acids were analyzed by HPLC-DAD and HPLC-UV, respectively. The results showed that
chanterelle is characterized by the presence of six phenolic compounds (3-, 4-, and 5-O-caffeoylquinic
acid, caffeic acid, p-coumaric acid, and rutin) and five organic acids (citric, ascorbic, malic, shikimic,
and fumaric acids). Samples preserved in olive oil also exhibited hydroxytyrosol, tyrosol, luteolin,
and apigenin, whereas conservation in vinegar led to the detection of hydroxytyrosol, tyrosol, and
tartaric acid in the analyzed samples. The conservation procedures to which chanterelle samples
were subjected seem to affect the qualitative and quantitative phenolics and organic acids profiles
Quantitation of nine organic acids in wild mushrooms
The organic acids composition of six wild edible mushroom species ( Amanita caesarea, Boletus edulis, Gyroporus castaneus, Lactarius deliciosus, Suillus collinitus, and Xerocomus chrysenteron) was
determined by an HPLC-UV detector method. The results showed that all of the samples presented
a profile composed of at least five organic acids: citric, ketoglutaric, malic, succinic, and fumaric
acids. Several samples also contained oxalic, ascorbic, quinic, and shikimic acids. In a general way,
the quantitation of the identified compounds indicated that malic acid, followed by the pair citric plus
ketoglutaric acids, were the main compounds in the analyzed species, with the exception of A.
caesarea, in which malic and ascorbic acids were the most abundant compounds. The relative
amounts and the presence/absence of each identified compound may be useful for the differentiation
of the species
Analysis and quantification of flavonoidic compounds from Portuguese olive (Olea europeae L.) leaf cultivars
Twenty three samples of 18 Portuguese olive leaf cultivars were analysed by a reversed-phase HPLC/DAD
procedure and eight flavonoidic compounds were identified and quantified (luteolin 7,40-O-diglucoside, luteolin
7-O-glucoside, rutin, apigenin 7-O-rutinoside, luteolin 40-O-glucoside, luteolin, apigenin and diosmetin).
Luteolin 7,40-O-diglucoside and luteolin 40-O-glucoside were identified by HPLC/DAD/MS/MS – ESI. The
studied olive leaf samples showed a common phenolic pattern, in which luteolin 40-O-glucoside was almost
always the major compoun
Ribonucleotide reductase inhibitors suppress SAMHD1 ara‐CTPase activity enhancing cytarabine efficacy
The deoxycytidine analogue cytarabine (ara‐C) remains the backbone treatment of acute myeloid leukaemia (AML) as well as other haematological and lymphoid malignancies, but must be combined with other chemotherapeutics to achieve cure. Yet, the underlying mechanism dictating synergistic efficacy of combination chemotherapy remains largely unknown. The dNTPase SAMHD1, which regulates dNTP homoeostasis antagonistically to ribonucleotide reductase (RNR), limits ara‐C efficacy by hydrolysing the active triphosphate metabolite ara‐CTP. Here, we report that clinically used inhibitors of RNR, such as gemcitabine and hydroxyurea, overcome the SAMHD1‐mediated barrier to ara‐C efficacy in primary blasts and mouse models of AML, displaying SAMHD1‐dependent synergy with ara‐C. We present evidence that this is mediated by dNTP pool imbalances leading to allosteric reduction of SAMHD1 ara‐CTPase activity. Thus, SAMHD1 constitutes a novel biomarker for combination therapies of ara‐C and RNR inhibitors with immediate consequences for clinical practice to improve treatment of AML
Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV
Results are presented from a search for a W' boson using a dataset
corresponding to 5.0 inverse femtobarns of integrated luminosity collected
during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV.
The W' boson is modeled as a heavy W boson, but different scenarios for the
couplings to fermions are considered, involving both left-handed and
right-handed chiral projections of the fermions, as well as an arbitrary
mixture of the two. The search is performed in the decay channel W' to t b,
leading to a final state signature with a single lepton (e, mu), missing
transverse energy, and jets, at least one of which is tagged as a b-jet. A W'
boson that couples to fermions with the same coupling constant as the W, but to
the right-handed rather than left-handed chiral projections, is excluded for
masses below 1.85 TeV at the 95% confidence level. For the first time using LHC
data, constraints on the W' gauge coupling for a set of left- and right-handed
coupling combinations have been placed. These results represent a significant
improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe
Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV
A search for a Higgs boson decaying into two photons is described. The
analysis is performed using a dataset recorded by the CMS experiment at the LHC
from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an
integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross
section of the standard model Higgs boson decaying to two photons. The expected
exclusion limit at 95% confidence level is between 1.4 and 2.4 times the
standard model cross section in the mass range between 110 and 150 GeV. The
analysis of the data excludes, at 95% confidence level, the standard model
Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The
largest excess of events above the expected standard model background is
observed for a Higgs boson mass hypothesis of 124 GeV with a local significance
of 3.1 sigma. The global significance of observing an excess with a local
significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is
estimated to be 1.8 sigma. More data are required to ascertain the origin of
this excess.Comment: Submitted to Physics Letters
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