94 research outputs found
Radical scavenging activity, lipid peroxidation inhibition and redox profile of aminodiarylamines in the thieno[3,2-b]pyridine series
The reducing properties of diarylamines make them very important as antioxidants, especially as
radical scavengers as it has been demonstrated by our and other research groups [1 -3]. Three
di(hetero)arylamines were prepared by C- N coupling of the methyl3-amino-6-bromothieno(3,2-
b]pyridine-2-carboxylate with bromonitrobenzenes and further reduced to the amino compounds 1a-c
(Scheme) (4].FCT for financial support through the NMR Portuguese network (Bruker 400 Avance 111-Univ Minho).
To FCT and FEDER-COMPETE/QREN/EU for financial support through the research unities PEstC/
QUI/UI686/2011 and PEst-OE/AGR/UI0690/2011 , the research project PTDC/QUI-QUI/111 060/2009
and the post-Doctoral grant attributed to R.C.C. (SFRH/SPD/68344/201 0) also financed by POPH and
FSE
Lipid peroxidation inhibition, free radical scavenging activity and electrochemical behaviour of a dihydroxylated di(hetero)arylamine
The skin provides the first line of defense against oxidative damage
induced by environmental factors, having an elaborated antioxidant
system designed to deal with free radicals and oxidative stress. However,
under severe stress conditions this biological response is not sufficient,
leading to oxidative damage and, in consequence, to skin disorders,
immunosuppresion, premature skin aging and ultimately cancer
Spectra of weighted algebras of holomorphic functions
We consider weighted algebras of holomorphic functions on a Banach space. We
determine conditions on a family of weights that assure that the corresponding
weighted space is an algebra or has polynomial Schauder decompositions. We
study the spectra of weighted algebras and endow them with an analytic
structure. We also deal with composition operators and algebra homomorphisms,
in particular to investigate how their induced mappings act on the analytic
structure of the spectrum. Moreover, a Banach-Stone type question is addressed.Comment: 25 pages Corrected typo
Insights in the antioxidant activity of diarylamines from the 2,3-dimethylbenzo[b]thiophene through the redox profile
Cyclic voltammetry was used to evaluate the antioxidant activity of 7-aryl or 7-heteroarylamino-2,3-dimethylbenzo[b]thiophenes previously synthesized by some of us, comparing their oxidation potentials with those of the well-known synthetic standards (BHA, BHT). Compounds with electron-donating groups on the arylamine moiety have lower Ep/2 than compounds with electron-withdrawing groups or electron-deficient rings (pyridines). The position of the methoxy group on the arylamine moiety also changes the oxidation potential: lower Ep/2 for the diarylamines with methoxy groups in the para position. Comparing the first peak potential with the ones of BHA and BHT, the diarylamine compounds show lower oxidation potential, and therefore higher reducing power. A reasonable inverse correlation was also observed between the Ep/2 values and the pEC50 values obtained in antioxidant activity chemical assays. It can be generalized that compounds with lower Ep/2 values have better antioxidant activity (DPPH assay) and higher reducing power
Evaluation of the antioxidant properties of diarylamines in the benzo[b]thiophene series by free radical scavenging activity and reducing power
The antioxidant properties of substituted diarylamines in the benzo[b]thiophene series were evaluated by their reducing
power and free radical scavenging activity. The results were compared with those of standards: acid ascorbic for the first method and
BHA and BHT for the second. For both methods it was possible to establish some structure–activity relationships (SARs) based on
the position of the arylamination on the benzo[b]thiophene moiety, the presence of different substituents on the phenyl ring (F, 1 or 2
OMe) and on the thiophene ring (H, CO2Et, CO2H)
Chemical characterization, antioxidant, anti-inflammatory and cytotoxic properties of bee venom collected in Northeast Portugal
Bee venom (BV) or apitoxin is a complex mixture of substances with reported biological activity. In the present work, five bee venom samples obtained from Apis mellifera iberiensis from the Northeast Portugal (two different apiaries) were chemically characterized and evaluated for their antioxidant, anti-inflammatory and cytotoxic properties. The LC/DAD/ESI-MS(n) analysis of the samples showed that melittin was the most abundant compound, followed by phospholipase A2 and apamin. All the samples revealed antioxidant and anti-inflammatory activity but without a direct relation with any of the individual chemical components identified. The results highlight that there are specific concentrations (present in BV5) in which these compounds are more active. The BV samples showed similar cytotoxicity for all the tested tumour cell lines (MCF-7, NCI-H460, HeLa and HepG2), being MCF-7 and HeLa the most susceptible ones. Nevertheless, the studied samples seem to be suitable to treat breast, hepatocellular and cervical carcinoma because at the active concentrations, the samples were not toxic for non-tumour cells (PLP2). Regarding the non-small cell lung carcinoma, BV should be used under the toxic concentration for non-tumour cells. Overall, the present study corroborates the enormous bioactive potential of BV being the first report on samples from Portugal.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support to CIMO (PEst-OE/AGR/UI0690/2014) and R.C. Calhelha grant (SFRH/BPD/68344/2010)
Signal and System Approximation from General Measurements
In this paper we analyze the behavior of system approximation processes for
stable linear time-invariant (LTI) systems and signals in the Paley-Wiener
space PW_\pi^1. We consider approximation processes, where the input signal is
not directly used to generate the system output, but instead a sequence of
numbers is used that is generated from the input signal by measurement
functionals. We consider classical sampling which corresponds to a pointwise
evaluation of the signal, as well as several more general measurement
functionals. We show that a stable system approximation is not possible for
pointwise sampling, because there exist signals and systems such that the
approximation process diverges. This remains true even with oversampling.
However, if more general measurement functionals are considered, a stable
approximation is possible if oversampling is used. Further, we show that
without oversampling we have divergence for a large class of practically
relevant measurement procedures.Comment: This paper will be published as part of the book "New Perspectives on
Approximation and Sampling Theory - Festschrift in honor of Paul Butzer's
85th birthday" in the Applied and Numerical Harmonic Analysis Series,
Birkhauser (Springer-Verlag). Parts of this work have been presented at the
IEEE International Conference on Acoustics, Speech, and Signal Processing
2014 (ICASSP 2014
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