Gavino Sanna

RP-HPLC determination of water-soluble vitamins in honey

The assessment and validation of reliable analytical methods for the determination of vitamins in sugar-based matrices (e.g. honey) are still scarcely explored fields of research. This study proposes and fully validates a simple and fast RP-HPLC method for the simultaneous determination of five water-soluble vitamins (vitamin B(2), riboflavin; vitamin B(3), nicotinic acid; vitamin B(5), pantothenic acid; vitamin B(9), folic acid; and vitamin C, ascorbic acid) in honey. The method provides low detection and quantification limits, very good linearity in a large concentration interval, very good precision, and the absence of any bias. It has been successfully applied to 28 honey samples (mainly from Sardinia, Italy) of 12 different botanical origins. While the overall amount of the analytes in the samples is quite low (always below 40 mg kg(-1)), we have observed a marked dependence of some of their concentrations (i.e. vitamin B(3) and vitamin B(5)) and the botanical origin of the honey. This insight might lead to important characterization features for this food item.

An RP-HPLC determination of 5-hydroxymethylfurfural in honey The case of strawberry tree honey.

The use of the RP-HPLC official method of the International Honey Commission (IHC) for the determination of 5-hydroxymethylfurfural (HMF) in strawberry tree honey (Arbutus unedo, a typical Sardinian honey) has brought to light a specific and heavy chromatographic interference that prevents accurate quantification. The interference has been identified as homogentisic acid (HA), i.e. the marker of the botanical origin of the honey. For this reason, an alternative RP-HPLC method is proposed. The bias-free method allows a complete separation of HMF from HA to the baseline level and is faster and more precise than the RP-HPLC official method: the detection and quantification limits are 1.9 and 4.0mgkg(-1), respectively, whereas the repeatability is ca. 2% in the HMF concentration range of 5-140mgkg(-1).

A direct RP-HPLC method for the determination of furanic aldehydes and acids in honey.

In this study 5-hydroxymethyl-2-furaldehyde (HMF), 2-furaldehyde, 3-furaldehyde, 2-furoic acid and 3-furoic acid are contemporarily determined in honey using a swift and direct RP-HPLC approach. The validation protocol was performed in terms of detection and quantification limits, precision (by repeatability and reproducibility), linearity and accuracy (by recovery tests); the acceptability of the precision and accuracy results was positively verified using Horwitzs model and AOAC guidelines, respectively. The method was tested on 18 honey samples of different ages, and botanical and geographical origin. HMF and 2-furaldehyde correlated highly with the age of the samples, whereas no correlation was observed with regards to 2-furaldehyde and 2-furoic acid. Hypotheses relating to the formation of minority furanic compounds are also proposed.

The Role of Irrigation Techniques in Arsenic Bioaccumulation in Rice (Oryza sativa L.)

The bioaccumulation of arsenic compounds in rice is of great concern worldwide because rice is the staple food for billions of people and arsenic is one of the most toxic and carcinogenic elements at even trace amounts. The uptake of arsenic compounds in rice comes mainly from its interaction with system soil/water in the reducing conditions typical of paddy fields and is influenced by the irrigation used. We demonstrate that the use of sprinkler irrigation produces rice kernels with a concentration of total arsenic about fifty times lower when compared to rice grown under continuous flooding irrigation. The average total amount of arsenic, measured by a fully validated ICP-MS method, in 37 rice grain genotypes grown with sprinkler irrigation was 2.8 ± 2.5 μg kg(-1), whereas the average amount measured in the same genotypes grown under identical conditions, but using continuous flooding irrigation was 163 ± 23 μg kg(-1). In addition, we find that the average concentration of total arsenic in rice grains cultivated under sprinkler irrigation is close to the total arsenic concentration found in irrigation waters. Our results suggest that, in our experimental conditions, the natural bioaccumulation of this element in rice grains may be completely circumvented by adopting an appropriate irrigation technique.

Structural and functional modifications of human aorta proteoglycans in atherosclerosis.

Proteoglycans (PGs) were extracted from minced normal human aorta intima and media and adjacent atherosclerotic plaques. Samples obtained from each individual artery which showed different degrees of atherosclerotic involvement were studied separately. Comparing normal and atherosclerotic areas from the same aorta, the hexuronic acid content was always lower in the atherosclerotic minces. Atherosclerotic samples always contained a higher percentage amount of chondroitinase AC resistant material. PGs were sequentially extracted with increasing guanidine hydrochloride (GuHCl) concentrations. 0.4 M GuHCl extracted about 13% of total PGs, containing mostly chondroitin sulphate (CS), whilst 4 M GuHCl extracted about 50% of total PGs, containing CS, dermatan sulphate (DS), heparan sulphate and hyaluronic acid. PGs from atherosclerotic minces showed a higher DS amount, based on electrophoretic glycosaminoglycan (GAG) analysis. PGs extracted with 4 M GuHCl were further characterized by gel-chromatography and by CsCl density gradient centrifugation. The relative content of PGs with highest hydrodynamic size appeared to be markedly reduced in all the atherosclerotic samples. LDL/GAGs and LDL/PGs interactions were studied by affinity chromatography. GAGs obtained by papain digestion of PGs extracted from atherosclerotic areas contained a glycosaminoglycuronan interacting more strongly with human LDL than GAGs from normal areas of the same artery. The complete elution of PGs required higher NaCl concentration than GAGs. Moreover, PGs from atherosclerotic samples showed higher affinity for LDL than PGs from normal areas of the same aorta.

Electrochemical and spectroelectrochemical study of copper complexes with 1,10-phenanthrolines

The redox behaviour of a series of copper(II) complexes with different phenanthrolines (1:2 metal to ligand) in dimethylformamide solvent is reported. Cyclic voltammetry, controlled potential coulometry and spectroelectrochemistry in the visible region have been used. Accurate values for the formal potential of the copper(II)/ copper(I) couples could be computed by spectroelectrochemistry, also in those cases in which the systems are poorly reversible. Two further reductions lead to neutral and anionic copper species, respectively. The nature of the substituents on the phenanthroline ligands has been found to affect strongly the redox potential of the former couples, while a less marked influence on the latter ones has been evidenced. On the other hand, differences in the ligands induce very different kinetic stability of the copper complexes formed in the more cathodic processes.

Density and volumetric properties of ethane-1,2-diol + di-ethylen-glycol mixtures at different temperatures

Abstract The density of the ethane-1,2-diol (ED)+di-ethylen-glycol (DEG) binary mixtures has been measured at different temperatures over the complete composition range. The experimental measurements have been used to check the validity of relationships accounting for the dependence of the density on temperature and composition, useful to obtain interpolated values in the correspondence of the experimental data gaps. Starting from the primary data, some derived quantities, such as partial molar volumes, excess and partial excess molar volumes, have been obtained. In these mixtures, VE presents an S-shaped dependence on composition at each temperature, showing negative values in the ED rich-region and positive values at the opposite extreme. The results are compared and discussed to get light to the changes in molecular association and structural effects in this solvent system.

Electrochemical behaviour of cyclometallated gold(III) complexes. Evidence of transcyclometallation in the fate of electroreduced species

Abstract The electrochemical behaviour of a series of neutral and cationic N–C and N–N–C cyclometallated gold(III) species: ([Au(py1)(Cl)2], Hpy1=2-benzylpyridine; [Au(bipyn)(Cl)][PF6], Hbipy1=6-benzyl-2,2′-bipyridine, Hbipy2=6-(1-methylbenzyl)-2,2′-bipyridine, Hbipy3=6-(1,1-dimethylbenzyl)-2,2′-bipyridine, Hbipy4=6-phenyl-2,2′-bipyridine) has been investigated in different solvent systems using cyclic voltammetry and controlled-potential coulometry. All the species considered show, in cyclic voltammetry, an irreversible one-electron reduction in the potential range −0.9/−1.2 V versus Fc+/0, using a Pt electrode. On the other hand, exhaustive coulometries have shown the consumption of a number of Faraday per mole within the range 1–2. The very complex decomposition of the electrogenerated species affords elemental gold and significant amounts of different gold by-products. In some situations (e.g. reduction of [Au(bipy4)(Cl)][PF6]), working with 0.1 mol dm−3 Na[PF6], CH3CN solvent system, it has been possible to characterise the most abundant gold(III) compound, by NMR, FAB-MS, and elemental analysis. The analytical and spectroscopic data provide evidence for the N–C bis-cyclometallated gold(III) derivative (e.g. [Au(bipy4)2][PF6]); the result entails quite an unusual transcyclometallation process. The same compound can also be obtained, albeit in very minor yield, by chemical reduction of [Au(bipy4)(Cl)][PF6].

Synthesis, electron paramagnetic resonance and X-ray structure characterization of copper(II) ternary complexes of p-aminobenzoic and 3,4-dimethoxyhydrocinnamic acid with phenanthrolines

Dimers of the type [Cu(pAb)(phen)(H2O)]2(NO3)2· 2pAbH · 2H2O (1) and [Cu(DPP)(4,7-phen)(H2O)]2(NO3)2· 2H2O (2)(pAbH =p-aminobenzoic acid, DPPH = 3,4-dimethoxhydrocinnamic acid, phen = 1,10-phenanthroline and 4,7-phen = 4,7-dimethyl-1,10-phenanthroline) have been synthesized and characterized by means of EPR spectra in the solid and liquid states at room and low temperature, by magnetic measurements and by X-ray structure (1). Antiferromagnetic coupling of the unpaired electrons on each copper atom is evidenced by EPR spectra for both the compounds. They are, in fact, characteristic of dimers in which bridging nitrogen ligands are present. The Cu–Cu distance is 3.060 (1)A and the dimer results through the bridging of two symmetry-related pAb molecules by bidentate carboxylic groups. The two phenanthroline molecules in the dimer are stacked with a minimum distance of 3.39 (1)A.

Recent Advances in the Analysis of Phenolic Compounds in Unifloral Honeys

Honey is one of the most renowned natural foods. Its composition is extremely variable, depending on its botanical and geographical origins, and the abundant presence of functional compounds has contributed to the increased worldwide interest is this foodstuff. In particular, great attention has been paid by the scientific community towards classes of compounds like phenolic compounds, due to their capability to act as markers of unifloral honey origin. In this contribution the most recent progress in the assessment of new analytical procedures aimed at the definition of the qualitative and quantitative profile of phenolic compounds of honey have been highlighted. A special emphasis has been placed on the innovative aspects concerning the extraction procedures, along with the most recent strategies proposed for the analysis of phenolic compounds. Moreover, the centrality of validation procedures has been claimed and extensively discussed in order to ensure the fitness-for-purpose of the proposed analytical methods. In addition, the exploitation of the phenolic profile as a tool for the classification of the botanical and geographical origin has been described, pointing out the usefulness of chemometrics in the interpretation of data sets originating from the analysis of polyphenols. Finally, recent results in concerning the evaluation of the antioxidant properties of unifloral honeys and the development of new analytical approaches aimed at measuring this parameter have been reviewed.