Sonoprocessing: mechanisms and recent applications of power ultrasound in food.

There is a growing interest in using green technologies in the food industry. As a green processing technique, ultrasound has a great potential to be applied in many food applications. In this review, the basic mechanism of ultrasound processing technology has been discussed. Then, ultrasound technology was reviewed from the application of assisted food processing methods, such as assisted gelation, assisted freezing and thawing, assisted crystallization, and other assisted applications. Moreover, ultrasound was reviewed from the aspect of structure and property modification technology, such as modification of polysaccharides and fats. Furthermore, ultrasound was reviewed to facilitate beneficial food reactions, such as glycosylation, enzymatic cross-linking, protein hydrolyzation, fermentation, and marination. After that, ultrasound applications in the food safety sector were reviewed from the aspect of the inactivation of microbes, degradation of pesticides, and toxins, as well inactivation of some enzymes. Finally, the applications of ultrasound technology in food waste disposal and environmental protection were reviewed. Thus, some sonoprocessing technologies can be recommended for the use in the food industry on a large scale. However, there is still a need for funding research and development projects to develop more efficient ultrasound devices.

Combined effect of pH treatment and the extraction pH on the physicochemical, functional and rheological characteristics of amaranth (Amaranthus hypochondriacus) seed protein isolates.

Results for the effect of extraction pH and pH treatment on the functional, physicochemical, rheological and thermal characteristics of amaranth protein isolates (APIs) are reported in this study. Four amaranth protein isolates (P1, P2, P3 and P4) were prepared by varying the extraction pH (9-11). These four protein isolate samples were further treated at pH values from 3 to 9. The total protein content and purity of protein isolates were found to be higher for P1 than P2, P3 and P4 samples. The particle size of P1 was significantly (p ≤ 0.05) higher (299.68 µm) than other samples. Solubility, emulsifying capacity and stability, foaming properties, water and oil binding capacities were higher for the P1 sample treated at pH 9. Gelation characteristics like storage modulus (G') and loss modulus (G") were higher for P1 samples. APIs obtained at extraction pH 9 (P1) also exhibited better thermal properties in comparison with other three samples.

Sequential multicomponent site-selective synthesis of 4-iodo and 5-iodopyrrole-3-carboxaldehydes from a common set of starting materials by tuning the conditions.

A simple and straightforward method for the synthesis of 4-iodo and 5-iodopyrrole-3-carboxaldehydes is developed from a common set of starting materials by tuning the reaction conditions. This sequential multicomponent protocol involves I2-mediated regioselective C4-iodination and aromatization of intermediate dihydropyrrole, generated through proline-catalyzed direct Mannich reaction-cyclization sequence between succinaldehyde and imines, to access 4-iodopyrroles. While aerobic oxidative aromatization of dihydropyrrole to pyrrole followed by NIS-mediated regioselective iodination furnished 5-iodopyrroles in a two-pot fashion. A series of site-selective C4/C5-iodopyrroles have been synthesized in good to high yields (up to 78%) and DFT calculations of these compounds were also performed.

Enantio- and Diastereoselective Two-Pot Synthesis of Isoquinuclidines from Glutaraldehyde and N-Aryl Imines with DFT Calculations.

A pot-economic method for the enantio- and diastereoselective synthesis of a [2.2.2] azabicyclic isoquinuclidine system is developed. This protocol involves the proline-catalyzed direct Mannich reaction-cyclization/IBX-mediated site-selective oxidation/NaBH4-reduction sequence between glutaraldehyde and imines to generate in situ chiral 1,2-DHPs, followed by the diastereoselective Diels-Alder reaction with N-aryl maleimides furnishing isoquinuclidines in overall five steps. A variety of isoquinuclidines having five-contiguous chiral centers, including an all-carbon quaternary, were prepared with high yields (up to 78%) and excellent stereoselectivity (>50:1 dr, and up to >99:1 er). DFT calculations support the observed high stereoselective reaction outcome.

Structural modification of quinoa seed protein isolates (QPIs) by variable time sonification for improving its physicochemical and functional characteristics.

High intensity ultrasound treatment (HIUS) by probe method is a novel technique to impart desirable physical, structural and functional characteristics to the native proteins structures. In this concern, effect of HIUS treatment at variable intervals from 5 to 35 min on quinoa seed protein isolates (QPIs) characteristics was analyzed. A typical dynamic rheological characteristic curve of QPIs had been obtained as a result of HIUS treatments at variable time intervals. Higher sonication resulted in the formation of large protein aggregates with higher particle size which increased QPIs turbidity. Temperature and frequency sweep tests had shown dominance of storage modulus over loss modulus, thus described strong gelling behavior of treated QPIs. HIUS treatment reduced particle size of QPIs with improved its flow properties. No splitting of bands had occurred due to sonication, whereas, more intensity of bands of treated QPIs depicted its greater water solubility. HIUS treatment decreased fluorescence intensity of QPIs whereas, no significant changes in Amide-II & III regions of QPIs occurred except decrease in wave number. The effects of HIUS on QIPs isolates had shown completely different response than those of results of quinoa protein extracts. Moreover, the studies conducted on quinoa protein extracts provided detailed information about the effect of HIUS on structural changes and its impact on physicochemical, functional and rheological characteristics.

Effect of pH and holding time on the characteristics of protein isolates from Chenopodium seeds and study of their amino acid profile and scoring.

Alkali extraction and acid precipitation methods were adopted to isolate protein from quinoa and album seeds of variety Chenopodium. Different pH dispersions (3-11) of isolated proteins were prepared and effects of pH and holding time on protein characteristics were evaluated. The pH-10 of extraction medium was found suitable for protein extraction on the basis of yield, purity, solubility and colour having isoelectric pH of 4.5. Yield and purity of protein isolates (PI) of quinoa and album varied from 8.12 to 12.22%; 74.19 to 85.07% and 7.71 to 10.98%; 77.16 to 86.12%, respectively. Overall, pH and time had significant effect on functional properties of PI of both seeds. Quinoa PI had higher emulsifying activity, emulsion stability, water binding capacity and dispersibility, whereas, foaming capacity and stability were higher for album PI. Nutritional indices were 64.20 and 64.58 for quinoa and album PI, respectively, whereas, amino acid scoring (FAO, 2013) indicated, isoleucine, leucine and valine as the limiting amino acids.

Enantiospecific Total Syntheses of (+)-Hapalindole H and (-)-12-epi-Hapalindole U.

Enantiospecific total syntheses of (+)-hapalindole H and (-)-12-epi-hapalindole U as well as the formal syntheses of (+)-hapalindole Q and (+)-12-epi-fischerindole U isothiocyanate have been described. Key steps of our approach feature expedient, highly regio- and diastereoselective Lewis acid catalyzed Friedel-Crafts reaction of indole with cyclic allylic alcohols and intramolecular reductive Heck reaction. Efficiency of the synthetic route also relies on an alkynyl aluminate complex driven regioselective nucleophilic epoxide opening from a sterically hindered site.

One-pot sequential multicomponent reaction between in situ generated aldimines and succinaldehyde: facile synthesis of substituted pyrrole-3-carbaldehydes and applications towards medicinally important fused heterocycles.

An efficient sequential multi-component method for the synthesis of N-arylpyrrole-3-carbaldehydes has been developed. This reaction involved a proline-catalyzed direct Mannich reaction-cyclization sequence between succinaldehyde and in situ generated Ar/HetAr/indolyl-imines, followed by IBX-mediated oxidative aromatization in one-pot operation. The practical utility of this procedure is shown at gram-scale and the synthesis of diverse bioactive fused heterocyclic scaffolds such as pyrroloquinoline, pyrrolo-oxadiazole, dihydro pyrroloquinoline, and pyrrolo-phenanthridine.

Enantioselective Synthesis of N-PMP-1,2-dihydropyridines via Formal [4 + 2] Cycloaddition between Aqueous Glutaraldehyde and Imines.

A simple and highly practical one-pot formal [4 + 2] cycloaddition approach for the enantioselective synthesis of N-PMP-1,2-dihydropyridines (DHPs) is described. This chemistry involves an amino-catalytic direct Mannich reaction/cyclization followed by IBX-mediated chemo- and regioselective oxidation sequence between readily available aqueous glutaraldehyde and imines under very mild conditions. A series of N-PMP-1,2-DHPs have been prepared in high yields and excellent enantioselectivity. This method also gives access to both enantiomers of 1,2-DHPs in surplus amount by shifting the catalyst configuration.

Linear dialdehydes as promising substrates for aminocatalyzed transformations.

Organocatalytic domino reactions involving amine activation of carbonyl compounds have become the latest chemical technology towards the design and development of useful synthetic methods. In this direction, linear dialdehydes such as succinaldehyde, glutaraldehyde, and other homologous compounds have attracted considerable attention as suitable substrates for amine catalyzed transformations. Due to their unique structural features, dialdehydes can easily engage in recreation of cascade/tandem transformations for the synthesis of valuable natural products and drug molecules. In this review article we discuss the current scenario and potential applications of linear dialdehydes as adequate synthetic substrates for amine catalyzed transformations to access biologically important complex scaffolds.

Highly enantioselective [4+2] annulation via organocatalytic Mannich-reductive cyclization: one-pot synthesis of functionalized piperidines.

A new method for one-pot synthesis of 2,3-substituted piperidine from N-PMP aldimine and aqueous glutaraldehyde via formal [4+2] cycloaddition is reported. This reaction involves organocatalytic direct Mannich reaction-reductive cyclization with high yields (up to 90%) and excellent enantioselectivities (up to >99%). The practicability of this method is also shown at a gram scale as well as through the synthesis of functionalized (-)-anabasine.

Asymmetric trienamine catalysis: new opportunities in amine catalysis.

Amine catalysis, through HOMO-activating enamine and LUMO-activating iminium-ion formation, is receiving increasing attention among other organocatalytic strategies, for the activation of unmodified carbonyl compounds. Particularly, the HOMO-raising activation concept has been applied to the greatest number of asymmetric transformations through enamine, dienamine, and SOMO-activation strategies. Recently, trienamine catalysis, an extension of amine catalysis, has emerged as a powerful tool for synthetic chemists with a novel activation strategy for polyenals/polyenones. In this review article, we discuss the initial developments of trienamine catalysis for highly asymmetric Diels-Alder reactions with different dienophiles and emerging opportunities for other types of cycloadditions and cascade reactions.

An organocatalytic direct Mannich-cyclization cascade as [3+2] annulation: asymmetric synthesis of 2,3-substituted pyrrolidines.

A new method for asymmetric synthesis of 2,3-substituted pyrrolidines from N-PMP aldimines and succinaldehyde via formal [3+2] cycloaddition is reported. This reaction involves proline catalyzed direct Mannich reaction and acid catalyzed reductive cyclization with high yields (up to 78%) and excellent enantioselectivities (up to >99%).

4-Meth-oxy-N-(4-nitro-benz-yl)aniline.

In the title compound, C(14)H(14)N(2)O(3), the nitro group is nearly coplanar with the benzene ring to which it is bonded [dihedral angle = 1.70 (2)°], and this ring is para-substituted by the amino-methyl-ene group. The dihedral angle between the benzene rings is 57.8 (1)°. The crystal structure is stabilized by N-H⋯O and C-H⋯O hydrogen bonds and weak C-H⋯π inter-actions are also observed.