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Abstract: This work reports the development of an automatic methodology based on the use of 1-anilinonaphthalene-8-sulfonate (ANS) as an interfacial fluorescent probe for detecting the hydrophobic environment shift around the probe, caused by the hydrolytic action of PLA2 on the liposomes. The implementation of this reaction in a sequential injection analysis (SIA) system along with the use of the mixing chambers permitted the evaluation of PLA2 activity and assessment of the inhibitory effect of the non-steroidal anti-inflammatory drugs (NSAIDs) on PLA2 activity. Several studies were performed with the aim of establishing the appropriate flow system configuration: the liposome substrate; PLA2 and ANS optimum concentrations and incubation times before and after the enzyme addition. Based on these studies, the optimum reaction conditions were selected. It was shown that PLA2 is effectively inhibited by the NSAIDs tested (meloxicam, tolmetin and ibuprofen) and by the α-lipoic acid, used as a positive control. Results obtained from the flow system are in agreement with those provided by the comparison batch procedures. The proposed methodology is in fact more efficient and rapid than the comparison batch experiments, enabling the exact timing of fluidic manipulations and precise control of the reaction conditions. [Copyright &y& Elsevier]

Abstract: Redox reactions are the heart of numerous biochemical pathways found in cellular chemistry, generating reactive oxygen species (ROS) and reactive nitrogen species (RNS), that includes superoxide anion radical (O2 −), hydrogen peroxide (H2O2), hydroxyl radical (HOt oxygen (1O2), hypochlorite anion (OCl−), peroxynitrite anion (ONOO−) and nitric oxide radical (NOasurement of scavenging capacity against these reactive species presents new challenges, which can be met by flow injection analysis (FIA). In the present review several methods based on FIA and also on its predecessors computer-controlled techniques (sequential injection analysis, multisyringe flow injection analysis, multicommutated and multipumping flow systems) are critically discussed. The selectivity and applicability of the methodology, the generation and detection of the target reactive species, the benefits and limitations of automation when compared to batch methods are some of the issues addressed. [Copyright &y& Elsevier]

Abstract: The role and importance of antioxidants in different fields, ranging from physiology to food technology, have become evident in the past years, requiring adequate analytical methodologies. Therefore, the determination of antioxidant capacity as a routine or screening analysis fosters its automation. In this context, several flow injection methods based on scavenging of 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulphonate) radical cation (ABTS +) or 2,2-diphenyl-1-picrylhydrazyl radical (DDPHd on the determination of total reducing capacity have been proposed. The objective of the present review is to critically compare the different approaches, regarding their degree of automation, their performance vs. the respective batch procedure and its applicability to real samples. [Copyright &y& Elsevier]

Abstract: Studies on the complexation of copper(II) by phenolic acids, as ligand models of humic substances were done by potentiometry. The acids under study were: 3,4-dihydroxyhydrocinnamic acid or hydrocaffeic acid (1), 3,4-dihydroxyphenylacetic acid (2) and 3,4-dihydroxybenzoic acid or protocatechuic acid (3). Acidity constants of the ligands and the formation constants of metal–ligand complexes were evaluated by computer programs. The carboxylic group of the phenolic acids has different pK a1 values, being the dissociation constants intrinsically related with the distance between the function and the aromatic nucleus. The results obtained allow concluding that acidity constants of the catechol moiety of the compounds are similar with pK a2 and pK a3 values between 9.47–9.41 and 11.55–11.70. The complexation properties of the three ligands towards copper(II) ion are quite similar, being the species found not different either in nature or stability. Although the model ligands have some structural differences no significant differences were found in their complexation properties towards copper(II). So, it can be postulated that complexation process is intrinsically related with the presence of a catechol group. [Copyright &y& Elsevier]