We report the synthesis of methyl esters of 3-(4-hydroxyphenyl)propionic, 3-(3,4-dihydroxyphenyl)propionic, 3-(3,5-dihydroxyphenyl)propionic, and 3-(3,4,5-trihydroxyphenyl)propionic acids and their ...use in a convergent iterative strategy to prepare up to four generations of three libraries, one of 3,4,5- and two of constitutional isomeric 3,4- and 3,5-substituted 3-phenylpropyl dendrons. Each library contains 3-3,4,5-tris(dodecyl-1-oxy)phenylpropyl-, 3-3,4-bis(dodecyl-1-oxy)phenylpropyl-, 3-{3,4-bis3-(4-dodecyl-1-oxyphenyl)propyl-1-oxyphenyl}propyl-, and 3-{3,4,5-tris3-(4-dodecyl-1-oxyphenyl)propyl-1-oxyphenyl}propyl ether first-generation dendrons on their periphery and −CO2CH3, −COOH, and −CH2OH groups at their apex. Regardless of their generation number and their periphery, internal, and apex structures, these dendrons self-assemble into supramolecular dendrimers that self-organize into all periodic and quasi-periodic assemblies encountered previously and in several unencountered with architecturally related benzyl ether-based supramolecular dendrimers. A variety of porous columnar lattices that were previously obtained only from dendritic dipeptides and hollow supramolecular spheres were also discovered from these building blocks. The more flexible and less compact 3-phenylpropyl ether repeat units are stable under acidic conditions, facilitate a simpler synthetic strategy, provide faster dynamics of self-assembly into higher-order supramolecular structures of larger dimensions, exhibit lower transition temperatures than the corresponding benzyl ether homologues, and demonstrate the generality of the self-assembly concept based on amphiphilic dendrons.
The study describes an improved version of the reverse-phase-HPLC method. To determine free resveratrol isomers, the method uses isocratic elution and electrochemical detection with the use of a ...glassy working electrode at a potential of 0.75 V. The effects of important factors – such as the isomerization of standard resveratrol solution in diffused daylight and its dependence on temperature or resveratrol isomerization in wine samples – were investigated. The equilibrium between
trans- and
cis-isomer was achieved after a 5-h exposure to the daily diffused light and it was not significantly influenced by the temperature (30–60 °C). Linearity was obtained in the concentration range from 0.01 to 10 mg
l
−1. The detection limit (
S/
N=3) was 3 μg
l
−1 for
trans-resveratrol and 15 μg
l
−1 for
cis-resveratrol. The
trans- and
cis-resveratrol were determined in selected Czech red and white wines and in the extract from
Vitis vinifera plant. The concentration of
trans-resveratrol ranged from 0.7 to 11 mg
l
−1, that of
cis-resveratrol from 0.6 to 5.1 mg
l
−1.
3-MCPD esters are contaminants that can form during refining of vegetable oils in the deodorization step. It was experimentally shown that their content in the vegetable oil depends on the acid value ...of the vegetable oil and the chloride content. 3-MCPD esters form approximately 2–5 times faster from diacylglycerols than from monoacylglycerols. It has been proved that the higher fatty acids content in the oil caused higher 3-MCPD esters content in the deodorization step. Neutralization of free fatty acids in the vegetable oil before the deodorization step by alkaline carbonates or hydrogen carbonates can completely suppress the formation of 3-MCPD esters. Potassium salts are more effective than sodium salts.
General, efficient and inexpensive methods for the synthesis of dendritic building blocks methyl 3′,4′‐dihydroxybiphenyl‐4‐carboxylate, 3′,5′‐dihydroxybiphenyl‐4‐carboxylate, and methyl ...3′,4′,5′‐trihydroxybiphenyl‐4‐carboxylate were elaborated. In all syntheses the major step involved an inexpensive NiII‐catalyzed Suzuki cross‐coupling reaction. These three building blocks were employed together with methyl 4′‐hydroxybiphenyl‐4‐carboxylate in a convergent iterative strategy to synthesize seven libraries containing up to three generations of 3′,4′‐, 3′,5′‐, and 3′,4′,5′‐substituted biphenyl‐4‐methyl ether based amphiphilic dendrons. These dendrons self‐assemble into supramolecular dendrimers that self‐organize into periodic assemblies. Structural and retrostructural analysis of their assemblies demonstrated that these dendrons self‐assemble into hollow and non‐hollow supramolecular dendrimers exhibiting dimensions of up to twice those reported for architecturally related dendrons based on benzyl ether repeat units. These new dendrons expand the structural diversity and demonstrate the generality of the concept of self‐assembling dendrons based on amphiphilic arylmethyl ethers.
Self‐assembling amphiphilic dendrons generated from combinations of AB, constitutional isomeric AB2, and AB3 biphenyl‐4‐methyl ether building blocks (see scheme) were used to explore and expand the structural diversity of non‐hollow and hollow supramolecular dendrimers, and to demonstrate the generality of the concept of self‐assembling dendrons based on amphiphilic arylmethyl ethers.
Hybrid dendrimers, obtained by complete monofunctionalization of the peripheral amines of a “zero‐generation” polyethyleneimine dendrimer, provide structurally diverse lamellar, columnar, and cubic ...self‐organized lattices that are less readily available from other modified dendritic structures. The reaction of tris(2‐aminoethyl)amine (TREN) with 4‐dodecyloxybenzimidazolide provides only the corresponding zero‐generation TREN dendrimer. From the mixture of tri‐ and disubstituted TREN derivatives obtained from first‐generation self‐assembling dendritic imidazolides, the hybrid dendrimer and a twin dendron could be separated, purified, and characterized. The hybrid dendrimers display smectic, columnar hexagonal (Φh), and cubic (Pm$\bar 3$n) lattices. The TREN twin dendrons, on which only two peripheral amines have been acylated, exhibit centered‐rectangular columnar (Φr‐c), Φh, and Pm$\bar 3$n lattices. The existence of a thermoreversible Φh‐to‐Pm$\bar 3$n phase transition in the first‐generation hybrid dendrimers and twin dendrons is exploited to elucidate an epitaxial relationship between the two mesophases. We postulate a mechanism by which the transition proceeds. The thermoreversible Φh‐to‐Pm$\bar 3$n phase change is accompanied by optical property changes that are suitable for rudimentary signaling or logic functions. This structural diversity reflects the quasiequivalence of flat‐taper and conical self‐assembling dendrons and the ability of flexible dendrimers to accommodate concomitant conformational and shape changes.
Versatile building blocks: Hybrid dendrimers and twin dendrons comprised of a zero‐generation polyethyleneimine core with self‐assembling dendrons at the periphery (see structure) exhibit structural diversity usually only found in higher generation dendritic molecules. With this complexity, a glimpse is obtained of the mechanism by which thermotropic hexagonal columnar and cubic lattices interconvert.
Antimicrobial and antioxidant properties of phenolic acids alkyl esters Merkl, R.,Vysoka Skola Chemicko-technologicka, Prague (Czech Republic). Ustav Technologie Mleka a Tuku; Hradkova, I.,Vysoka Skola Chemicko-technologicka, Prague (Czech Republic). Ustav Technologie Mleka a Tuku; Filip, V.,Vysoka Skola Chemicko-technologicka, Prague (Czech Republic). Ustav Technologie Mleka a Tuku ...
Czech Journal of Food Sciences,
01/2010, Volume:
28, Issue:
4
Journal Article
Peer reviewed
Open access
The aim of this study was to prepare some phenolic acids alkyl esters (methyl, ethyl, propyl, butyl and hexyl) and to determine their antioxidant and antimicrobial activities. The antimicrobial ...activity against Escherichia coli DMF 7503, Bacillus cereus DMF 2001, Listeria monocytogenes DMF 5776, Fusarium culmorum DMF 0103, and Saccharomyces cerevisiae DMF 1017 was investigated and expressed by minimum inhibitory concentration (MIC) in the range of 1.2-20mM. The inhibitory activity of phenolic acids butyl esters was found to be higher than that of methyl esters (MIC below 1.25mM). The antioxidant activity of the selected phenolic acids alkyl esters was investigated by Rancimat method. The esters of 3,4-dihydroxyphenolic acids (protocatechuic and caffeic acids) exhibited higher antioxidant activities in comparison with the respective phenolic acids. The highest antioxidant activity was found in the case of caffeic alkyl esters.
Lactobacilli in the vaginal tract are essential to protect against microbial infections. We therefore focused on isolating vaginal lactobacilli from pregnant women and testing their functional ...properties. Lactobacilli were isolated from 50 vaginal swabs and the purified isolates were identified by MALDI-TOF MS. Functional properties (antimicrobial activity, organic acids and hydrogen peroxide production, antibiotic susceptibility, auto-aggregation, and hydrophobicity) of selected isolates were tested. Lactobacilli (41 strains) were identified in 58% of swabs with a predominance of
Lactobacillus crispatus
(48%) followed by
L. jensenii
(21%),
L. rhamnosus
(14%),
L. fermentum
(10%), and
L. gasseri
(7%). The highest antibacterial activity was determined for
L. fermentum
and
L. rhamnosus
. Strong anti-
Candida
activity was observed for strains
L. crispatus
,
L. fermentum
, and
L. rhamnosus
. Strain
L. jensenii
58C possessed the highest production of hydrogen peroxide (6.32 ± 0.60 mg/l). The best lactic acid producer was strain
L. rhamnosus
72A (11.6 ± 0.2 g/l). All strains were resistant to fluconazole and metronidazole. The highest auto-aggregation was observed for strain
L. crispatus
51A (98.8 ± 0.1% after 24 h). Strain
L. rhamnosus
68A showed the highest hydrophobicity (69.1 ± 1.4%). Strains
L. fermentum
and
L. rhamnosus
showed high antibacterial activity and hydrophobicity, and strains
L. crispatus
possessed high auto-aggregation and anti-
Candida
activity. Thus, these strains alone or in a mix could be used for the preparation of probiotic products for treatment and prevention of vulvovaginal infections of pregnant and non-pregnant women.
Microbial adhesion to surfaces and the subsequent biofilm formation may result in contamination in food industry and in healthcare-associated infections and may significantly affect postoperative ...care. Some plants produce substances with antioxidant and antimicrobial properties that are able to inhibit the growth of food-borne pathogens. The aim of our study was to evaluate antimicrobial and anti-biofilm effect of baicalein, resveratrol, and pterostilbene on
Candida albicans
,
Staphylococcus epidermidis
,
Pseudomonas aeruginosa
, and
Escherichia coli
. We determined the minimum inhibitory concentrations (MIC), the minimum adhesion inhibitory concentration (MAIC), and the minimum biofilm eradication concentration (MBEC) by crystal violet and XTT determination. Resveratrol and pterostilbene have been shown to inhibit the formation of biofilms as well as to disrupt preformed biofilms. Our results suggest that resveratrol and pterostilbene appear potentially very useful to control and inhibit biofilm contaminations by
Candida albicans
,
Staphylococcus epidermidis
, and
Escherichia coli
in the food industry.
Palm oil is the vegetable oil refined and modified in the largest amount. In this study, we present the effect of wet fractionation and hydrogenation of RBD palm oil on the removal of 3-MCPD and ...glycidyl esters. Fractionated palmstearins had significantly decreased contents of 3-MCPD esters (71–74%) and glycidyl esters (21–26%), whereas top olein contained the highest levels of processing-induced contaminants accompanied by polar compounds. Exhaustive hydrogenation conditions caused rapid degradation of 3-MCPD esters (51–70%) in high melting palm oil products. Reduction of glycidyl esters (1–42%) was dependent on the type of nickel catalyst. The effect of iodine value drop on the contaminant degradation was shown to be linear. The combined action of dry-reduced, supported, 22% Ni and Raney nickel catalysts was found to be an optimal. Adsorptive bleaching and deodorization of hydrogenated palm stearin impacted particularly repeated formation of glycidyl esters up to 1.01–1.76 mg/kg, while 3-MCPD esters remained under the input RBD palm oil level. The mechanism of the catalyst action was investigated with glycidyl-
d
5
palmitate, 3-MCPD-
d
5
-1,2-dipalmitate. They were transformed into non-carcinogenic and non-genotoxic products by hydrogenolysis and deoxygenation reactions.
In order to understand the crystallization behavior of complex systems such as fats, fist we need to study each component separately, and then their binary and tertiary mixtures. Here, we used X-Ray ...diffraction and differential scanning calorimetry to analyze the phase behavior of 2-oleoyl-1-palmitoyl-3-stearoyl-
rac
-glycerol (POS) and 2-linoleoyl-1-palmitoyl-3-stearoyl-
rac
-glycerol (PLS) binary mixtures. Both triacylglycerols were synthesized in our laboratory to obtain pure components (> 99%) and mixed in different concentration ratios to obtain 11 mixtures. The mixtures were analyzed after rapid cooling to −15 °C and after 96 h of storage at 30 °C by X-ray powder diffraction and differential scanning calorimetry. We investigated the melting temperatures and mutual interactions of sub-α, α and γ polymorphic forms of PLS with sub-α, α and pseudo-β’ polymorphic forms of POS. Under the applied conditions, we did not observe more stable polymorphic modifications of PLS. Based on the obtained data, we proposed the phase diagram of binary mixture, which can be useful for modeling a fat structuring system for food and cosmetic applications. These results provide a deeper understanding of the crystallization behavior of fats, including such a complex issue as cocoa butter crystallization.
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