Modified micellar electrokinetic chromatography in the analysis of catechins and xanthines in chocolate

Modified micellar electrokinetic chromatography (MEKC) analysis of monomeric flavanols (catechin and epicatechin) and methylxanthines (caffeine and theobromine) in chocolate and cocoa was performed by using sodium dodecyl sulfate (SDS) as a principal component of the running buffer. Because of the reported poor stability of catechins in alkaline solutions, acidic conditions (pH 2.5) were chosen and consequently the electroosmotic flow (EOF) was significantly suppressed; this resulted in a fast anodic migration of the analytes partitioned into the SDS micelles. Under these conditions, variations of either pH value in acidic range or SDS concentration, showed to be not suitable to modulate the selectivity. To overcome this limit, use of additives to the SDS-based running buffer was successfully applied and three different systems were optimized for the separation of (+)-catechin, (-)-epicatechin, caffeine, and theobromine in chocolate and cocoa powder samples. In particular, two mixed micelle systems were applied; the first consisted of a mixture of SDS and 3-[(3-cholamidopropyl)dimethylammonio]-1-propansulfonate (CHAPS) with a composition of 90 mM and 10 mM, respectively; the second was SDS and taurodeoxycholic acid sodium salt (TDC) with a composition of 70 mM and 30 mM, respectively. A further MEKC approach was developed by addition of 10 mM hydroxypropyl-beta-cyclodextrin (HP-beta-CD) to the SDS solution (90 mM); it provided a useful cyclodextrin(CD)-modified MEKC. By applying the optimized conditions, different separation profiles of the flavanols and methylxanthines were obtained showing interesting potential of these combined systems; their integrated application showed to be useful for the identification of the low level of (+)-catechin in certain real samples. The CD-MEKC approach was validated and applied to the determination of catechins and methylxanthines in aqueous extracts from four different commercial chocolate types (black and milk) and two cocoa powders.     

A New Preparation of 1,3,3‐Trimethylbicyclo[2.2.2]octan‐2,6‐dione,a Never Isolated Intermediate in a Total Synthesis of (+)‐Norpatchoulenol. Formal Total Synthesis of (±)‐Iso‐Norpatchoulenol

A new preparation and the isolation and spectroscopic characterization of 1,3,3‐trimethylbicyclo[2.2.2]octan‐2,6‐dione ( 3 ), a so far elusive key intermediate in the Liu–Ralitsch total synthesis of (+)‐norpatchoulenol ((+)‐ 1a ), is described. The preparation of 3 constitutes also a formal total synthesis of (±)‐iso‐norpatchoulenol ((±)‐ 1b ), since 3 is correlated to an intermediate in the Monti and co‐workers synthesis of (±)‐ 1b .     

Agro-industrial waste enzymes: Perspectives in circular economy

According to the Food and Agriculture Organization of the United Nations, approximately 1.3 billion tons of food is wasted each year, equivalent to approximately one-third of world production. Agri-food wastes are the source of proteins, carbohydrates, lipids, and other essential minerals that have been exploited for value-added products by the development of biorefineries and sustainable business as important elements of circular economies. The innovation and materialization of these types of processes, including the use of disruptive technologies on microbial bioconversion and enzyme technology, such as nanotechnology, metabolic engineering, and multi-omics platforms, increase the perspectives on the waste valorization process. Lignocellulolytic enzymes, pectinases, and proteases are mainly used as catalyzers on agri-food waste treatment, and their production in house might be the trend in near future for agro-industrial countries. Another way to transform the agri-food wastes is via aerobic or anaerobic microbial process from fungal or bacterial cultures; these processes are the key to produce waste enzymes.     

Reaction of thiete 1,1-dioxide with α-chlorobenzalphenylhydrazine and methyl phenylhydrazonochloroacetate

Thiete 1,1-dioxide reacts with 2 moles of α-chlorobenzalphenylhydrazine and methyl phenylhydrazonochloroacetate in the presence of triethylamine leading to the pyrazole derivatives 6 and 7 whose structure and mechanism of formation are discussed.     

Enantioseparations of polyhalogenated 4,4’-bipyridines on polysaccharide-based chiral stationary phases and molecular dynamics simulations of selector–selectand interactions

2’-(4-Pyridyl)- and 2’-(4-hydroxyphenyl)-TCIBPs (TCIBP = 3,3’,5,5’-tetrachloro-2-iodo-4,4’-bipyridyl) are chiral compounds that showed interesting inhibition activity against transthyretin fibrillation in vitro. We became interested in their enantioseparation since we noticed that the M-stereoisomer is more effective than the P-enantiomer. Based thereon, we recently reported the enantioseparation of 2’-substituted TCIBP derivatives with amylose-based chiral columns. Following this study, herein we describe the comparative enantioseparation of both 2’-(4-pyridyl)- and 2’-(4-hydroxyphenyl)-TCIBPs on four cellulose phenylcarbamate-based chiral columns aiming to explore the effect of the polymer backbone, as well as the nature and position of substituents on the side groups on the enantioseparability of these compounds. In the frame of this project, the impact of subtle variations of analyte and polysaccharide structures, and mobile phase (MP) polarity on retention and selectivity was evaluated. The effect of temperature on retention and selectivity was also considered, and overall thermodynamic parameters associated with the analyte adsorption onto the CSP surface were derived from van ’t Hoff plots. Interesting cases of enantiomer elution order (EEO) reversal were observed. In particular, the EEO was shown to be dependent on polysaccharide backbone, the elution sequence of the two analytes being P-M and M-P on cellulose and amylose tris(3,5-dimethylphenylcarbamate), respectively. In this regard, a theoretical investigation based on molecular dynamics (MD) simulations was performed by using amylose and cellulose tris(3,5-dimethylphenylcarbamate) nonamers as virtual models of the polysaccharide-based selectors. This exploration at the molecular level shed light on the origin of the enantiodiscrimination processes.     

The Additive Influence of Propane-1,2-Diol on SDS Micellar Structure and Properties

Micellar systems are colloids with significant properties for pharmaceutical and food applications. They can be used to formulate thermodynamically stable mixtures to solubilize hydrophobic food-related substances. Furthermore, micellar formation is a complex process in which a variety of intermolecular interactions determine the course of formation and most important are the hydrophobic and hydrophilic interactions between surfactant–solvent and solvent–solvent. Glycols are organic compounds that belong to the group of alcohols. Among them, propane-1,2-diol (PG) is a substance commonly used as a food additive or ingredient in many cosmetic and hygiene products. The nature of the additive influences the micellar structure and properties of sodium dodecyl sulfate (SDS). When increasing the mass fraction of propane-1,2-diol in binary mixtures, the c.m.c. values decrease because propane-1,2-diol is a polar solvent, which gives it the ability to form hydrogen bonds, decreasing the cohesivity of water and reducing the dielectric constant of the aqueous phase. The values of ΔGm0 are negative in all mixed solvents according to the reduction in solvophobic interactions and increase in electrostatic interaction. With the rising concentration of cosolvent, the equilibrium between cosolvent in bulk solution and in the formed micelles is on the side of micelles, leading to the formation of micelles at a lower concentration with a small change in micellar size. According to the ¹H NMR, with the addition of propylene glycol, there is a slight shift of SDS peaks towards lower ppm regions in comparison to the D₂O peak. The shift is more evident with the increase in the amount of added propane-1,2-diol in comparison to the NMR spectra of pure SDS. Addition of propane-1,2-diol causes the upfield shift of the protons associated with hydrophilic groups, causing the shielding effect. This signifies that the alcohol is linked with the polar head groups of SDS due to its proximity to the SDS molecules.     

Assembly of a supramolecular capsule on a molecular printboard

A molecular capsule based on ionic interactions between two oppositely charged calix[4]arenes, 1 and 2, was assembled both in solution and on a surface. In solution, the formation of the equimolar assembly 1.2 was studied by (1)H NMR, ESI-MS, and isothermal titration calorimetry, giving an association constant (K(a)) of 7.5 x 10(5) M(-1). A beta-cyclodextrin self-assembled monolayer (beta-CD SAM) on gold was used as a molecular printboard to anchor the tetraguanidinium calix[4]arene (2). The binding of tetrasulfonate calix[4]arene 1 was monitored by surface plasmon resonance spectroscopy. Rinsing of the surface with a high ionic strength aqueous solution allows the removal of the tetrasulfonate calix[4]arene (1), while by rinsing with 2-propanol it is possible to achieve the complete desorption of the tetraguanidinium calix[4]arene (2) from the beta-CD SAM. The K(a) for the capsule formation on a surface is 3.5 x 10(6) M(-1), thus comparing well with the K(a) determined in solution.     

Trinuclear pyrazine-bridged ruthenium complexes: syntheses, electrochemistry, NIR-Vis spectra, and their interpretation in terms of a 5-orbital-3-parameter model

A study of absorption spectra in the near-infrared (NIR) and visible (vis) regions of trinuclear Ru complexes containing pyrazine (pyz) as bridging ligand, trans-[(Ru(NH(3))(5)pyz)(2)Ru(NH(3))(4)](m+)(m = 6-9), is reported. The spectra were recorded on aqueous solutions containing the described species formed in situ by stoichiometric additions of a standard solution of Ce(SO(4))(2). They were interpreted in terms of a simple 5-orbital-3-parameter model which includes the effects of d-pi interaction and electronic correlation. The model is shown to account for the observed NIR-vis spectra of the complex ions. The 6+ parent species was synthesized by an improved literature method and fully characterized. The novel 8+ complex was also prepared and characterized. The 9+ ion was established to be slowly reduced by water, with dioxygen formation. Electrochemical (CV and DPV) studies were performed on the trinuclear 6+ complex, as well as on its constituent fragments [Ru(NH(3))(5)(pyz)](2+) and trans-[Ru(NH(3))(4)(pyz)(2)](2+).     

Comprehensive two-dimensional chromatography in food analysis

Comprehensive two-dimensional (2D) chromatographic techniques can be considered innovative methods, only quite recently developed. Since their introduction to the chromatographic community, these techniques have been used in several fields and have gained an excellent reputation as valuable and powerful analytical tools. The revolutionary aspect of comprehensive multidimensional (MD) techniques, in respect to classical MD chromatography, is that the entire sample is subjected to the 2D advantage. The resulting unprecedented separating capacity makes these approaches prime choices when analysts are challenged with highly complex mixtures. Furthermore, in the case of automated systems, instrumental analysis times are roughly the same as in monodimensional applications. The present review reports various comprehensive chromatographic applications on different food matrices. The GC x GC section highlights two fundamental aspects for component separation/identification: the exceptional peak capacity and the formation of group types on the 2D space plane. The LC x LC section reports the employment in food analysis of a recently developed multidimensional normal-phase (NP)-reversed-phase (RP) high performance liquid chromatography (HPLC) system. Also reported are comprehensive LC x GC and packed column supercritical fluid chromatography (pSFC x pSFC) applications in this field.     

Synthesis of trimethylammoniumphenylthio-substituted phthalocyanines with different pattern of substitution

The base-catalyzed cyclotetramerization of 3-, 4- and 4,5-dimethylaminophenylthio phthalonitriles with zinc(II)acetate afforded 1(4),8(11),15(18),22(25)- and 2(3),9(10),16(17),23(24)-tetrasubstituted and 2,3,9,10,16,17,23,24-octasubstituted Zn(II)phthalocyanines, respectively. The statistical mixed condensation of the same phthalonitriles with 1,2-dicyanobenzene gave the corresponding mono- and disubstituted derivatives. Methylation of such products afforded a series of cationic Zn(II)phthalocyanines with different pattern of substitution, with potential use as photodynamic agents in microbial infections.