Nadia Spano

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.

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].

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.

Study of the short-term release of the ionic fraction of heavy metals from dental amalgam into synthetic saliva, using anodic stripping voltammetry with microelectrodes.

The present paper describes a fast and reproducible procedure, employing differential pulse stripping analysis technique with graphite microelectrodes, for the quantitative evaluation of the ionic fraction of heavy metals (namely Hg, Cu, and Zn) released from dental amalgams into synthetic saliva during 6-90 h contact between amalgam and saliva, after completion of the dental restoration (short-term release). The Zn(2+) concentration was evaluated by linear calibration, whereas Cu(2+) and Hg(2+) contents were estimated by the standard additions method. While the concentration of Zn(2+) ion does not increase significantly anymore after a 6-h contact (values from 288+/-12 to 346+/-12 mugdm(-3) at time of contact from 6 to 90 h, respectively), in the same time interval the concentration of both Cu(2+) and Hg(2+) ions progressively increases (from 38+/-6 to 197+/-4 mugdm(-3) and from 15+/-3 to 101+/-2 mugdm(-3), respectively). The results of the release tests reveal that Hg concentration is at the highest level of risk (HBM III), as identified by the three human biomonitoring categories suggested by the Institut für Wasser-, Boden- und Lufthygiene des Umweltbundesamtes (Germany) for the estimation of potential harmful effects on health due to exposure to heavy metals.

Strawberry-Tree Honey Induces Growth Inhibition of Human Colon Cancer Cells and Increases ROS Generation: A Comparison with Manuka Honey

Honey is a natural product known to modulate several biological activities including cancer. The aim of the present study was to examine the phytochemical content and the antioxidant activity of Strawberry tree (Arbutus unedo) honey (STH) and its cytotoxic properties against human colon adenocarcinoma (HCT-116) and metastatic (LoVo) cell lines in comparison with Manuka (Leptospermum scoparium) honey (MH). Several unifloral STH and MH were analyzed for their phenolic, flavonoid, amino acid and protein contents, as well as their radical scavenging activities. STH from the Berchidda area showed the highest amount of phenolic, flavonoid, amino acid and protein content, and antioxidant capacity compared to MH. Both STH and MH induced cytotoxicity and cell death in a dose- and time-dependent manner in HCT-116 and LoVo cells, with less toxicity on non-cancer cells. Compared to MH, STH showed more effect at lower concentrations on HCT-116 and LoVo cells. In addition, both honeys increased intracellular reactive oxygen species (ROS) generation. In HCT-116 cells, STH and MH induced similar ROS production but in LoVo cells STH induced a higher percentage of ROS compared to MH. Our results indicate that STH and MH can induce cell growth inhibition and ROS generation in colon adenocarcinoma and metastatic cells, which could be due to the presence of phytochemicals with antioxidant properties. These preliminary results are interesting and suggest a potential chemopreventive action which could be useful for further studies in order to develop chemopreventive agents for colon cancer.

Microelectrodes for the Determination of Heavy Metal Traces in Physiological Conditions. Hg, Cu and Zn Ions in Synthetic Saliva

The present article reports an introductory study aimed to define voltammetric methodologies employing microelectrodes for the quantitative evaluation of Hg and other heavy metals in physiological-like matrices as synthetic saliva. The utilization of graphite, Pt and Au microdisc electrodes as voltammetric sensors in the differential-pulse stripping analysis of Hg, Cu, Ag, Sn and Zn (the main constituents of the well-known dental or silver amalgams, largely used for the dental restoration) has been studied in different artificial saliva. The best analytical performances, in terms of detection limit, repeatability and width of the potential window available, have been shown by graphite electrodes. Co-deposition effects (e.g., Pb or Cd) play an important role in improving detection limit and repeatability of the responses of graphite electrodes in the determination of Hg. The conditions for contemporary determination of Hg, Cu and Zn in a single re-oxidation step are also established and selected experimental conditions are proposed by virtue of the absence of Cu-Zn intermetallic interference in the deposition step. On the other hand, the study has shown that no possible combination of experimental conditions, i.e., nature of electrode and saliva, presence or absence of other reducible ions, allows the detection of Ag and Sn at µg dm -3 levels.

Electrochemical properties of gold(III) complexes with 2,2′-bipyridine and oxygen ligands

The electrochemical behavior of a series of five cationic species containing the Au(bipy) 3 moiety and additional oxygen-donor ligands, and of the relevant common precursor, i.e. the dichloride [Au(bipy)Cl2][PF6] species, have been investigated using cyclic voltammetry and controlled-potential coulometry. All the compounds with oxygen-containing ligand(s) (2‐6) undergo an easy, irreversible one-electron reduction process. The first reduction process of the dichloride consists of an equally easy but quasi-reversible charge transfer, as evidenced by voltammetric tests at a very high scan rate, followed by an irreversible second-order chemical reaction. Correlations between the relative values of the reduction potentials and the corresponding molecular structure are made and hypotheses on the nature of the reduction mechanisms are advanced.

Gas chromatography analysis of major free mono- and disaccharides in milk: Method assessment, validation and application to real samples

Saccharides are functional constituents of milk. Although d-lactose represents almost the totality of the saccharides in the milk, minor species, like d-glucose, d-galactose, myo-inositol and, as a result of severe thermal treatments, monosaccharides like d-tagatose, are also detectable. Although chromatography has been the main analytical approach used for accomplishing this task, quite surprisingly a validated gas chromatographic method aimed at the simultaneous determination of these compounds is still needed. Hence, our contribution is devoted to fill this gap. After the optimization of clean-up and derivatization (conversion of saccharides in their trimethyl silyl ethers) steps, the adoption of a highly cross-linked silphenylene stationary phase permitted to obtain high resolution and a fast chromatographic run. Validation was accomplished in terms of limit of detection, limit of quantification, linearity, precision, and trueness. The accuracy of the method was successfully tested on a number of partially skimmed milk samples. Excellent limits of detection for all analytes make this method eligible, also with respect to a gas chromatographic/mass spectrometry approach, for routine analysis and quality control in the dairy industries.