Recovery of Vanillin and Syringaldehyde from Lignin Oxidation: A Review of Separation and Purification Processes

Lignin is an underexploited side-stream of pulp and paper industry and biorefineries, being used for energy production at mill site or as low value material for dispersants or binding applications. However, an integrated process of reaction and separation can be implemented for the production of high added-value monomeric phenolic chemicals such as vanillin and syringaldehyde. In this review, the main research advances in the recovery of vanillin and syringaldehyde resulting from oxidation of lignin are addressed, covering various separation methodologies namely liquid-liquid extraction, supercritical fluid extraction, distillation, crystallization, membrane separation, and adsorption. Studies in this area started in the early years of the 20^th century, but in the last decades several processes have been suggested, mainly for vanillin separation. Finding the ultimate industrially feasible process is still a necessary task and this review points out the most promising technologies and sequence of processes.     

From Complex Natural Products to Simple Synthetic Mimetics by Computational De Novo Design

We present the computational de novo design of synthetically accessible chemical entities that mimic the complex sesquiterpene natural product (?)‐Englerin A. We synthesized lead‐like probes from commercially available building blocks and profiled them for activity against a computationally predicted panel of macromolecular targets. Both the design template (?)‐Englerin A and its low‐molecular weight mimetics presented nanomolar binding affinities and antagonized the transient receptor potential calcium channel TRPM8 in a cell‐based assay, without showing target promiscuity or frequent‐hitter properties. This proof‐of‐concept study outlines an expeditious solution to obtaining natural‐product‐inspired chemical matter with desirable properties.     

Nanostructuration Effect on the Thermal Behavior of Ionic Liquids

This work shows how the nanostructuration of ionic liquids (ILs) governs the glass and melting transitions of the bistriflimide imidazolium‐based [C_nC₁im][NTf₂] and [C_nC_nim][NTf₂] series, which highlights the trend shift that occurs at the critical alkyl size (CAS) of n=6. An initial increase in the glass temperature (T_g) with an increase in the alkyl side chain was observed due to the intensification of the dispersive interactions (van der Waals). Above the CAS, the ?CH₂? increment has the same effect in both glass and liquid states, which leads to a plateau in the glass transition after nanostructuration. The melting temperature (T_m) of the [C_nC₁im][NTf₂] and [C_nC_nim][NTf₂] series presents a V‐shaped profile. For the short‐alkyl ILs, the ?CH₂? increment affects the electrostatic ion pair interactions, which leads to an increase in the conformational entropy. The ?CH₂? increment disturbs the packing ability of the ILs and leads to a higher entropy value ( ) and consequently a decrease in T_m. Above the CAS, the ?CH₂? contribution to the melting temperature becomes more regular, as a consequence of the nanostructuration of the IL into polar and nonpolar domains. The dependence of the alkyl chain on the temperature, enthalpy, and entropy of melting in the ILs above the CAS is very similar to the one observed for the alkane series, which highlights the importance of the nonpolar alkyl domains on the ILs thermal behavior.     

Chemical Modification in the Design of Immobilized Enzyme Biocatalysts: Drawbacks and Opportunities

Chemical modification of enzymes and immobilization used to be considered as separate ways to improve enzyme properties. This review shows how the coupled use of both tools may greatly improve the final biocatalyst performance. Chemical modification of a previously immobilized enzyme is far simpler and easier to control than the modification of the free enzyme. Moreover, if protein modification is performed to improve its immobilization (enriching the enzyme in reactive groups), the final features of the immobilized enzyme may be greatly improved. Chemical modification may be directed to improve enzyme stability, but also to improve selectivity, specificity, activity, and even cell penetrability. Coupling of immobilization and chemical modification with site‐directed mutagenesis is a powerful instrument to obtain fully controlled modification. Some new ideas such as photoreceptive enzyme modifiers that change their physical properties under UV exposition are discussed.     

Multivariate optimization and HS-SPME/GC-MS analysis of VOCs in red, yellow and purple varieties of Capsicum chinense sp. peppers

Peppers are used not only in cookery, but also in many other applications, like cosmetic, pharmaceutical and nourishing industry. The chemical composition of peppers is quite complex and several volatile and non-volatile substances contribute to their flavor, which is an important sensorial propriety. In this work a headspace/solid phase microextraction/gas chromatography coupled to mass spectrometry method was developed to evaluate the profiles of volatile compounds that contribute to the aroma of red, yellow and purple varieties of Capsicum chinense sp. peppers. The optimization of the extraction conditions was carried out using multivariate strategies such as factorial design and response surface methodology. The GC-MS analysis allowed the tentative identification of 34 compounds, with similarities higher than 85%, in accordance with the NIST mass spectral library. The data obtained by the analysis of volatile compounds, according to the proposed method, were treated with PCA chemometrics tool in order to group different varieties of C. chinense sp. peppers with similar VOC profiles. Amongst the most abundant VOCs, hexyl ester of pentanoic acid, dimethylcyclohexanols, humulene and esters of butanoic acid were found. Principal component analysis turned possible to visualize the grouping tendencies of the studied varieties of pepper, as well as the identification of the volatile compounds responsible for discriminating the three groups. Considering the fact that many species of peppers are used as human food, the significance of this work is further emphasized by its applicability to the study of food quality indicators, and as a tool for investigations on the composition of the pepper sources.     

New bromotyrosine alkaloids from the marine sponge Psammaplysilla purpurea

Seven new bromotyrosine alkaloids Purpurealidin A, B, C, D, F, G, H and the known compounds Purealidin Q, Purpurealidin E, 16-Debromoaplysamine-4 and Purpuramine I have been isolated from the marine sponge Psammaplysilla purpurea. Their structure was elucidated on the basis of detailed 1D, 2D NMR and MS spectroscopic data. Purpurealidin B, 16-Debromoaplysamine-4 and Purpuramine I exhibited in vitro antimicrobial activities against E. coli, S. aureus, and V. cholerae. In addition, Purpurealidin B and 16-Debromoaplysamine-4 were also active against Shigella flexineri and Salmonella typhi while Purealidin Q was bactericidal only against Salmonella typhi.     

Thermal analysis of a polymorphic azo dye derived from 2-amino-5-nitrothiazole

An azo dye, derived from 2-amino-5-nitrothiazole and a substituted N,N-dimethyl aniline, was studied by various techniques. Two sets of proton signals were obtained by NMR in CDCl₃ solution, suggesting that two polymorphs coexist, however, only one set of signals is observed in DMSO solution. Differential scanning calorimetry and thermogravimetric analysis were used to confirm the existence of two forms. The events registered during thermal treatment of a sample were assigned to a glass transition, recrystallization and fusion of crystalline compounds. Hot-stage microscopy was used to obtain images of the dye samples at various stages of the heating program and these observations support the interpretation of the calorimetric results.     

Triterpene Esters Isolated from Leaves of Maytenus salicifolia Reissek

The triterpene ester (3β)‐olean‐18‐en‐3‐yl stearate ( 1 ), together with (3β)‐urs‐12‐en‐3‐yl stearate ( 2 ), and (3β)‐lup‐20(29)‐en‐3‐yl stearate ( 3 ) were isolated from leaves of Maytenus salicifolia Reissek (Celastraceae). The structure of 1 , a new compound, including its configuration, was established by ¹H, ¹³C, and DEPT‐135 NMR data, including 2D experiments (HSQC, HMBC, COSY, and NOESY). The molecular mass (692 Da) was confirmed by gas chromatography coupled with mass spectrometry (CG/MS).     

An INAA-based evaluation of the responses of epiphytic lichens to elemental inputs in an oceanic environment (Azores)

Within an extensive survey of prevalent lower and higher plants in the Azores’ islands, with a view to their monitoring potential for airborne elements at ground level, and then to an eventual use in evaluation routines for the archipelago, epiphytic lichens were collected from Cryptomeria japonica (Japanese cedar) trunks all across Terceira and Santa Maria islands. After suitable procedures, thalli samples were put through instrumental neutron activation analysis (INAA; k ₀-variant) for elemental concentrations. Providing an overall view of micro-and trace-element levels in representative foliose-and fruticose-type species, the data of high-level elements agree generally well for genera with distinct species, with a relatively low interspecies variability. Principal-component analysis of the whole set of results discriminates clearly between two morphological factors, corresponding to foliose and fruticose species, and likely among four major origins of elemental inputs: soil/dust (two factors), sea spray and an antimony-related source. All things considered, and accounting for its availability and ubiquity, Parmotrema bangii seems an adequate choice for further lichen-based, biomonitoring campaigns in the Azores archipelago.     

Optimization of inulinase production by Kluyveromyces marxianus using factorial design

Factorial design and response surface techniques were used to optimize the culture medium for the production of inulinase by Kluyveromyces marxianus. Sucrose was used as the carbon source instead of inulin. Initially, a fractional factorial design (2^5–1) was used in order to determine the most relevant variables for enzyme production. Five parameters were studied (sucrose, peptone, yeast extract, pH, and K₂HPO₄), and all were shown to be significant. Sucrose concentration and pH had negative effects on inulinase production, whereas peptone, yeast extract, and K₂HPO₄ had positive ones. The pH was shown to be the most significant variable and should be preferentially maintained at 3.5. According to the results from the first factorial design, sucrose, peptone, and yeast extract concentrations were selected to be utilized in a full factorial design. The optimum conditions for a higher enzymatic activity were then determined: 14 g/L of sucrose, 10 g/L of yeast extract, 20 g/L of peptone, 1 g/L of K₂HPO₄. The enzymatic activity in the culture conditions was 127 U/mL, about six times higher than before the optimization.