Giancarlo Marrosu

Recovery of natural antioxidants from spent coffee grounds.

Spent coffee grounds (SCG) were extracted with an environmentally friendly procedure and analyzed to evaluate the recovery of relevant natural antioxidants for use as nutritional supplements, foods, or cosmetic additives. SCG were characterized in terms of their total phenolic content by the Folin-Ciocalteu procedure and antioxidant activity by the DPPH scavenging assay. Flavonoid content was also determined by a colorimetric assay. The total phenolic content was strongly correlated with the DPPH scavenging activity, suggesting that phenolic compounds are mainly responsible for the antioxidant activity of SCG. An UHPLC-PDA-TOF-MS system was used to separate, identify, and quantify phenolic and nonphenolic compounds in the SCG extracts. Important amounts of chlorogenic acids (CGA) and related compounds as well as caffeine (CAF) evidenced the high potential of SCG, a waste material that is widely available in the world, as a source of natural phenolic antioxidants.

Thermal analysis of some α-amino acids with similar structures

Abstract The thermal analysis of some α-amino acids using simultaneous TG-DSC measurements and kinetic calculations by the dynamic TG technique have been carried out. With this technique, compounds with similar structures can be grouped by their thermograms which have the same shape, although this does not give enough information on their thermal structural variation. The thermodynamic and kinetic data are of different significance, except in the case of series where the rings of the side chains influence the thermal decomposition of the compounds.

Hypochlorite scavenging activity of hydroxycinnamic acids evaluated by a rapid microplate method based on the measurement of chloramines

Scavengers of hypochlorite (XOCI) could have beneficial effects in diseases in which this oxidant plays a pathogenic role. It has been reported that ferulic acid and chlorogenic acid, the quinic ester of caffeic acid, are good hypochlorite scavengers, but a systematic evaluation of the naturally occurring hydroxycinnamic acids (HCAs), which these substances belong to, has not been performed yet. Thus, in this work we studied, by two different in‐vitro methods, the antioxidant activity of five HCAs: p‐coumaric acid, ferulic acid, sinapinic acid, caffeic acid and chlorogenic acid. The methods applied in this study were based on the oxidation of human serum albumin (HSA) by XOCI, a new microplate method based on the measurement of chloramines and a previously described carbonyl assay. Firstly, lysine‐derived chloramines, in the presence or absence of the HCAs, were detected using 5‐thio‐2‐nitrobenzoic acid (TNB), measuring the absorbance at 415nm by a microplate reader. To remove excess XOCI, Trolox, a known XOCI scavenger, was added before TNB. Secondly, lysine‐derived carbonyls, in the presence or absence of the HCAs, were detected by using 2,4‐dinitro‐phenylhydrazine. Hydroxycinnamic acids appeared active (caffeic≥sinapinic>chlorogenic≅ferulic>p‐coumaric acid) by both methods, suggesting possible pharmacological applications for these compounds, which are present at high concentrations in the plant kingdom.

Oxidative stress parameters in different systemic rheumatic diseases

The involvement of oxidative stress in the pathogenesis of rheumatic disorders, such as systemic sclerosis (SSc) and chronic polyarthritides, has been suggested yet not thoroughly verified experimentally. We analysed 4 plasmatic parameters of oxidative stress in patients with SSc (n = 17), psoriatic arthritis (PsA) (n = 10) and rheumatoid arthritis (RA) (n = 9) compared with healthy subjects (n = 22). The biomarkers were: total antioxidant capacity (TAC) measured by ferric reducing antioxidant power (FRAP) method, hydroperoxides determined by ferrous ion oxidation in presence of xylenol orange (FOX) method and sulfhydryl and carbonyl groups assessed by spectrophotometric assays. The results showed significantly increased hydroperoxides in SSc, PsA and RA (3.97 ± 2.25, 4.87 ± 2.18 and 5.13 ± 2.36 μmol L−1, respectively) compared with the control group, (2.31 ± 1.40 μmol L−1; P < 0.05). Sulfhydryls were significantly lower in SSc (0.466 ± 0.081 mmol L −1), PsA (0.477 ± 0.059 mmol L−1) and RA (0.439 ± 0.065 mmol L−1) compared with the control group) (0.547 ± 0.066 mmolL−1; P < 0.05). TAC in all three diseases showed no difference in comparison with controls. Carbonyls were significantly higher in RA than in the control group (32.1 ± 42 vs 2.21 ± 1.0 nmol (mg protein)−1; P < 0.05). The obtained data indicate augmented free radical‐mediated injury in these rheumatic diseases and suggest a role for the use of antioxidants in mediated prevention and treatment of these pathologies.

Hypochlorite scavenging activity of flavonoids.

Scavengers of hypochlorite, a highly reactive oxidant produced by activated phagocytes, could have potential therapeutic effects in diseases in which this oxidant plays a pathogenic role. Flavonoids are polyphenolic substances present in food plants and have been extensively studied for their antioxidant properties against various free radicals. Less is known about their reactivity with hypochlorite. In this study, the hypochlorite scavenging activity of flavonoids was investigated using a microplate assay recently developed in our laboratory. This method evaluates the ability of a substance to inhibit the formation of chloramines in human serum albumin upon oxidation by hypochlorite. Thirteen flavonoids were tested. Most of them inhibited human serum albumin oxidation at micro‐molar concentrations and appeared more active than Trolox, a water‐soluble equivalent of vitamin E. It was observed that the greater the number of hydroxyl substitutions, the greater the scavenging activity. The 3‐hydroxy substitution seemed to be particularly important for scavenging activity, whereas the presence of a 2,3‐double bond in the C ring did not. Flavonoids were found to be good hypochlorite scavengers in‐vitro and further information is provided about the chemical aspects important for scavenging activity. Thus, flavonoids could have beneficial effects in diseases such as atherosclerosis in which hypochlorite plays a pathogenic role.

Chemical and Electrochemical Study on the Interactions of Aminoxyls with Superoxide Anion

The electrochemical behaviour of tetramethyl-pyrrolinic, -piperidinic, indolinonic and quinolinic aminoxyls and of oxygen was studied in DMFAI20 in order to evaluate the feasibility of an electron transfer process between aminoxyls and superoxide anion. The rate constants of these reactions were calculated by applying the Marcus theory. A new mechanism for the reaction, which operates in competition with those already reported in the literature involving an electron transfer process, is proposed. Copyright

Thermal analysis of some α-amino acids using simultaneous TG-DSC apparatus. The use of dynamic thermogravimetry to study the chemical kinetics of solid state decomposition

Abstract A study of the thermal stability of some α-amino acids by simultaneous TG-DSC measurements and kinetic calculations with the dynamic TG technique was carried out. Three different scales of thermal stability were found from the thermodynamic and kinetic data.

Thermodynamics of the second proton dissociation processes of nine α-amino-acids and the third ionization processes of glutamic acid, aspartic acid and tyrosine

Abstract The thermodynamics of the second proton dissociation processes for nine α-amino-acids were evaluated using electrochemical and calorimetric data. A calorimetric acid strength scale in water is presented. The acidity order is explained as a function of the solvation of the zwitterions and anions. The differences between the thermodynamics of the first and second ionization processes of the compounds result from the fact that the two processes involve different solvation processes. The anions of the compounds containing a hydroxyl group are less solvated than the anions of the α-amino-acids having a hydrophobic group.

A study on the interactions between coenzyme Q 0 and superoxide anion. Could ubiquinones mimic superoxide dismutase (SOD)

An electrochemical study was carried out on 1,4-benzoquinone, duroquinone, coenzymes Q0 and Q10 in the absence and in the presence of molecular oxygen in aprotic (DMF) and protic (DMF/H2O 95:5 (v/v)) media. Water was added because the investigated reactions are deeply influenced by the presence of protons. Q0 and Q10 exhibited a similar electrochemical behaviour. Since Q0 is more soluble in protic medium than the biologically more important analogue Q10, it was chosen as a model for a more detailed investigation. Voltammetric studies of Q0 carried out in aprotic and protic media in the presence of oxygen showed that, besides simple O2·− dismutation, the Q0 promoted dismutation of O2·− should also be considered. Spectroelectrochemical experiments with the same experimental conditions support the electrochemical results, showing that in the presence of superoxide and in aprotic medium semiquinone Q0·− gives rise to a disproportionation equilibrium, while in the presence of water it tends to be reoxidized to the starting Q0 by OOH·. EPR measurements are also in agreement with these results.

Protein oxidation markers in the serum and synovial fluid of psoriatic arthritis patients

The role of oxidative stress has been studied in rheumatoid arthritis (RA) and other inflammatory joint diseases to some extent, but its importance in psoriatic arthritis (PsA) has rarely been investigated. The aim of this study was to analyze the levels of protein oxidation markers, sulfhydryl (SH) and carbonyl (CO) groups, in the synovial fluid (SF) and serum of PsA patients and compare them with the findings in RA and osteoarthritis (OA) patients. A total of 49 subjects with a knee‐joint effusion including 16  PsA, 18  RA, and 15 OA patients were studied. In all patients, the levels of SH groups measured in the serum and SF inversely correlated with the number of white blood cells (WBC) (P<0.05) and the percentage of polymorphonuclear leukocytes (PMN) (P<0.01) in SF. Serum SH levels inversely correlated with serum erythrocyte sedimentation rate (ESR) (P<0.02) and C‐reactive protein (CRP) (P<0.05) values. The SH levels in SF were significantly lower in patients affected by PsA and RA compared to OA cases (P<0.02). The serum SH levels in PsA were lower than OA (P<0.001) and higher than RA patients (P<0.05). The serum and synovial levels of CO groups in PsA, RA, and OA patients were similar. Our study provides novel evidence on the involvement of protein oxidation in PsA and confirms the important role of oxidative stress in the pathogenesis of RA. These data suggest that antioxidant agents can potentially be a useful addition to the conventional therapy in the management of these diseases. J. Clin. Lab. Anal. 22:210–215, 2008.