Position Of Hydroxyl Groups Research Articles

SARs for the Antiparasitic Plant Metabolite Pulchrol. 3. Combinations of New Substituents in A/B-Rings and A/C-Rings.

The natural products pulchrol and pulchral, isolated from the roots of the Mexican plant Bourreria pulchra, have previously been shown to possess antiparasitic activity towards Trypanosoma cruzi, Leishmania braziliensis and L. amazonensis, which are protozoa responsible for Chagas disease and leishmaniasis. These infections have been classified as neglected diseases, and still require the development of safer and more efficient alternatives to their current treatments. Recent SARs studies, based on the pulchrol scaffold, showed which effects exchanges of its substituents have on the antileishmanial and antitrypanosomal activity. Many of the analogues prepared were shown to be more potent than pulchrol and the current drugs used to treat leishmaniasis and Chagas disease (miltefosine and benznidazole, respectively), in vitro. Moreover, indications of some of the possible interactions that may take place in the binding sites were also identified. In this study, 12 analogues with modifications at two or three different positions in two of the three rings were prepared by synthetic and semi-synthetic procedures. The molecules were assayed in vitro towards T. cruzi epimastigotes, L. braziliensis promastigotes, and L. amazonensis promastigotes. Some compounds had higher antiparasitic activity than the parental compound pulchrol, and in some cases even benznidazole and miltefosine. The best combinations in this subset are with carbonyl functionalities in the A-ring and isopropyl groups in the C-ring, as well as with alkyl substituents in both the A- and C-rings combined with a hydroxyl group in position 1 (C-ring). The latter corresponds to cannabinol, which indeed was shown to be potent towards all the parasites.

Corticosteroid Biosynthesis Revisited: No Direct Hydroxylation of Pregnenolone by Steroid 21-Hydroxylase.

Cytochrome P450s (CYPs) are an essential family of enzymes in the human body. They play a crucial role in metabolism, especially in human steroid biosynthesis. Reactions catalyzed by these enzymes are highly stereo- and regio-specific. Lack or severe malfunctions of CYPs can cause severe diseases and even shorten life. Hence, investigations on metabolic reactions and structural requirements of substrates are crucial to gain further knowledge on the relevance of different enzymes in the human body functions and the origin of diseases. One key enzyme in the biosynthesis of gluco- and mineralocorticoids is CYP21A2, also known as steroid 21-hydroxylase. To investigate the steric and regional requirements of substrates for this enzyme, we performed whole-cell biotransformation assays using a strain of fission yeast Schizosaccharomyces pombe recombinantly expressing CYP21A2. The progestogens progesterone, pregnenolone, and their 17α-hydroxy-derivatives were used as substrates. After incubation, samples were analyzed using gas chromatography coupled to mass spectrometry. For progesterone and 17α-hydroxyprogesterone, their corresponding 21-hydroxylated metabolites 11-deoxycorticosterone and 11-deoxycortisol were detected, while after incubation of pregnenolone and 17α-hydroxypregnenolone, no hydroxylated product was observed. Findings were confirmed with authentic reference material. Molecular docking experiments agree with these results and suggest that interaction between the 3-oxo group and arginine-234 of the enzyme is a strict requirement. The presented results demonstrate once more that the presence of an oxo-group in position 3 of the steroid is indispensable, while a 3-hydroxy group prevents hydroxylation in position C-21 by CYP21A2. This knowledge may be transferred to other CYP21A2 substrates and hence help to gain essential insights into steroid metabolism.

Effect of position of OH group in isomeric butanediols on intermolecular interaction with Choline Acetate: A thermodynamic study at different temperatures

The prominent effect of the position of hydroxyl groups in isomeric butanediols i.e.1,3-butanediol (1,3-BTD), 1,2-butanediol (1,2-BTD) and 2,3-butanediol (2,3-BTD) on intermolecular interactions with Choline Acetate has been investigated using various thermophysical parameters such as density ρ, speed of sound u, refractive index nD and specific conductivity κ over different concentration range and at temperatures varying from 293.15 to 323.15 K at atmospheric pressure. To gain further insight the derived parameters such as apparent molar volumes Vϕ, apparent molar isentropic compressibilities Ksϕ, and their infinite parameters mainly limiting apparent molar volumes at infinite dilution Vϕo, limiting apparent molar expansibilities Eϕo, limiting isentropic compression Kϕo, molar refraction Rm and infinite molar conductance ̂mo values have been calculated. The least values obtained for apparent molar volumes and compressibilities in case of 1,3-BTD mixtures are attributed to its highest ability to form intramolecular hydrogen bonding among isomeric butanediols and thus lesser availability to interact with Choline Acetate molecules. However for 2,3-BTD and 1,2-BTD binary mixtures the results have been explained on the basis of hydrophobic or iceberg effect where alkyl groups are present either on one end (1,2-BTD) or at both ends (2,3-BTD) while OH groups are located at vicinal carbon atoms.

Reactivity of Copper(I) Complexes Containing Ligands Derived from (1S,3R)‐Camphoric Acid with Dioxygen

AbstractAmine derivatives prepared from camphoric acid were used as ligands for the synthesis of corresponding copper(I) complexes. Their reactivity towards dioxygen was analyzed. The formation of a short‐lived bis(μ‐oxido)copper complex was spectroscopically observed during the reaction of the copper(I) complex with (1R, 3S)‐N1,N1,N3,N3‐Tetramethyl‐1,2,2‐trimethylcyclopentane‐1,3‐diamine as a ligand. Furthermore, a regioselective demethylation of the ligand system was detected. Deuteration of the methyl groups of the ligand allowed crystallization and characterization of the bis(μ‐oxido)copper complex. Derivatives of the ligand with pyridine residues caused suppression of the reactivity of the corresponding copper(I) complexes towards dioxygen. Additionally, the ligand system could be modified for intramolecular oxygenation reactions with benzaldehyde that led to the formation of salicylaldehyde, a selective hydroxylation in ortho position.

Recent Developments in Effective Antioxidants: The Structure and Antioxidant Properties.

Since the last few years, the growing interest in the use of natural and synthetic antioxidants as functional food ingredients and dietary supplements, is observed. The imbalance between the number of antioxidants and free radicals is the cause of oxidative damages of proteins, lipids, and DNA. The aim of the study was the review of recent developments in antioxidants. One of the crucial issues in food technology, medicine, and biotechnology is the excess free radicals reduction to obtain healthy food. The major problem is receiving more effective antioxidants. The study aimed to analyze the properties of efficient antioxidants and a better understanding of the molecular mechanism of antioxidant processes. Our researches and sparing literature data prove that the ligand antioxidant properties complexed by selected metals may significantly affect the free radical neutralization. According to our preliminary observation, this efficiency is improved mainly by the metals of high ion potential, e.g., Fe(III), Cr(III), Ln(III), Y(III). The complexes of delocalized electronic charge are better antioxidants. Experimental literature results of antioxidant assays, such as diphenylpicrylhydrazyl (DPPH) and ferric reducing activity power assay (FRAP), were compared to thermodynamic parameters obtained with computational methods. The mechanisms of free radicals creation were described based on the experimental literature data. Changes in HOMO energy distribution in phenolic acids with an increasing number of hydroxyl groups were observed. The antioxidant properties of flavonoids are strongly dependent on the hydroxyl group position and the catechol moiety. The number of methoxy groups in the phenolic acid molecules influences antioxidant activity. The use of synchrotron techniques in the antioxidants electronic structure analysis was proposed.

The Calcium-Activated Chloride Channel TMEM16A is Inhibitied by Liquiritigenin.

The transmembrane 16 (TMEM16) family contains 10 subtypes, and the function of each protein is different. TMEM16A is a calcium-activated chloride channel involved in physiological and pathological situations. Liquiritigenin is an aglycone derived from Glycyrrhiza glabra, and it is generated via the metabolism of enterobacterial flora. It has been known that liquiritigenin reduces pain sensation involving TMEM16A activation in primary sensory neurons. In addition, other pharmacological effects of liquiritigenin in physiological functions involving TMEM16A have been reported. However, the relationship between TMEM16A and liquiritigenin is still unknown. Therefore, we hypothesized that TMEM16A is inhibited by liquiritigenin. To confirm this hypothesis, we investigated the effect of liquiritigenin on TMEM16A currents evoked by intracellular free calcium in HEK293T cells transfected with TMEM16A. In this study, we found that liquiritigenin inhibited the mouse and human TMEM16A currents. To further confirm its selectivity, we also investigated its pharmacological effects on other ion channels, including transient receptor potential vanilloid 1 (TRPV1) and ankyrin 1 (TRPA1), which are non-selective cation channels involved in pain sensation. However, liquiritigenin did not inhibit the currents of TRPV1 and TRPA1 induced by capsaicin and allyl isothiocyanate, respectively. Therefore, our findings indicate that selective TMEM16A inhibition could be one molecular mechanism that explains liquiritigenin-induced pain reduction. Additionally, we also investigated the inhibitory effects of estrogens on TMEM16A because liquiritigenin reportedly binds to the estrogen receptor. In this study, a pregnancy-dependent estrogen, estriol, significantly inhibited TMEM16A. However, the efficacy was weak. Although there is a possibility that TMEM16A activity could be suppressed during pregnancy, the physiological significance seems to be small. Thus, the inhibitory effect of estrogen might not be significant under physiological conditions. Furthermore, we investigated the effect of dihydrodaidzein, which is an analog of liquiritigenin that has a hydroxyphenyl at different carbon atom of pyranose. Dihydrodaidzein also inhibited mouse and human TMEM16A. However, the inhibitory effects were weaker than those of liquiritigenin. This suggests that the efficacy of TMEM16A antagonists depends on the hydroxyl group positions. Our finding of liquiritigenin-dependent TMEM16A inhibition could connect the current fragmented knowledge of the physiological and pathological mechanisms involving TMEM16A and liquiritigenin.

Improvement in performance and combustion of CRDI engine with simarouba blended fuel as alternative fuel

This paper is concerned with the benefits of addition of 1-pentanol and benzyl alcohol, which are classified as aliphatic and aromatic type alcohols respectively based on the position of hydroxyl group, to a blend of Siarouba glauca and diesel (B20) in minor quantities. This was later tested under various load conditions to study the performance, emission, and combustion on a CRDI engine. Literature is cited to show that the poor performance of B20 can be enhanced substantially by the addition of 1-pentanol (P) and benzyl alcohol (Bn). Each sample of fuel was prepared by 5% concentration by volume addition of 1-pentanol and benzyl alcohol. The tests were conducted on a single-cylinder, four-stroke, and constant speed CRDI engine and compared with the results from which diesel was used as a fuel. Break thermal (BT) efficiency is found to be a considerable 9.08% and 5.5% more in 5%pentanol and 5% Benzyl Alcohol fuel blends respectively than that of diesel. While comparing brake specific fuel consumption (BSFC) it was found that diesel has a noticeable 24.32% more consumption rate than both the fuel types. The emission rate of CO was found to be 81.25% and 81.33% less with 5%pentanol and 5% Benzyl Alcohol fuel blends than that of diesel. Diesel also released .5714 and .2698 times more Hydrocarbon(HC) compared to 5%pentanol and 5% Benzyl Alcohol respectively. However, NOx emissions were higher in both 5%pentanol and 5% Benzyl Alcohol. These benefits are documented by comparing each fuel in different load conditions and are represented graphically.

Direct esterification of sucrose: novel lead-compounds against cancer

Introduction Phenylpropanoic sugar esters are a class of naturally occurring active substances, mainly found in ancient oriental medicinal plants (Figure 1), with a scope of activity ranging from antioxidant, antibacterial as well as anti-tumoral [1]. Though relatively simple in structure – owing to their resemblance to natural carbohydrates - few have been the successful attempts to obtain them in the laboratory, hampered mainly by the fact that the high similarity between functional groups in sugars restrains the feasibility of current methods and their reproducibility in industrial scales [2]. Our study aims for the development of reliable and effective methods for the synthesis of a library of phenylpropanoic esters derived from sucrose. Figure 1. Veronicastrum Sibiricum, one of the plants containing phenylpropanoic sucrose esters as the active substance. Materials and methods The lead-compounds are obtained by treating sucrose with a vigorous basic medium. The preferential esterification in the sugar hydroxyls is catalysed by a metal halide salt. The different compounds obtained are meant to be tested and screened for their biological applications, with particular emphasis on their action against cancer cells. Results Our most appealing discovery is the possibility of directly enhancing the regioselectivity of the 2, 3′, 6 and 6′-hydroxyl positions in the sugar moiety induced by transition-metal salts as catalysts [3] (Scheme 1). Different metal salts induce the different hydroxyls mentioned for a direct esterification with the acylating agent, which reflects the specificity and versatility of this novel class of reactions. Scheme 1. General route for the metal-chelate direct esterification of sucrose molecule. Discussion and conclusions We can conclude, so far, that cobalt and copper chloride salts give the best results in terms of yield (more than 30% conversion) and decreased reaction time (less than one hour). To further extend our knowledge about the metal-chelate directed acylation method, we are also experimenting with other halide salts, namely zinc, calcium, nickel and iron, as well as with derivatized molecules of sucrose. Thus, our work can certainly lead the development of novel drugs and resourceful cancer therapies.

Progress and Achievements in Glycosylation of Flavonoids.

In recent years, the chemistry of flavonoid glycosylation has undergone significant developments. This mini-review is devoted to summarizing existing strategies and methods for glycosylation of natural and synthetic flavonoids. Herein we overviewed the reaction conditions of flavonoid glycosylation depending on the position of hydroxyl groups in a parent molecule, the degree of it conjugation with the π-system, the presence of steric factors, the formation of intramolecular hydrogen bonds, etc. Especial attention was given to the choice of the glycosyl donor moiety, which has a significant effect on the yield of the final glycosidated products. Finally, a general strategy for regioselective glycosylation of flavonoids containing several hydroxyl groups is outlined.

Nanoconfinement Raises the Energy Barrier to Hydrogen Atom Exchange between Water and Glucose.

In bulk aqueous environments, the exchange of protons between labile hydroxyl groups typically occurs easily and quickly. Nanoconfinement can dramatically change this normally facile process. Through exchange spectroscopy (EXSY) NMR measurements, we observe that nanoconfinement of glucose and water within AOT (sodium bis(2-ethylhexyl) sulfosuccinate) reverse micelles raises the energy barrier to labile hydrogen exchange, which suggests a disruption of the hydrogen bond network. Near room temperature, we measure barriers high enough to slow the process by as much as 2 orders of magnitude. Although exchange rates slow with decreasing temperatures in these nanoconfined environments, the barrier we measure below ∼285 K is 3-5 times lower than the barrier measured at room temperature, indicating a change in mechanism for the process. These findings suggest the possibility of hydrogen tunneling at a surprisingly high-temperature threshold. Furthermore, differences in exchange rates depend on the hydroxyl group position on the glucose pyranose ring and suggest a net orientation of glucose at the reverse micelle interface.

Synthesis of quercetin based self-assembling supramolecular amphiphiles for amphotericin B delivery

Self-assembling amphiphilic molecules have been the subject of greater scientific interest owing to their applications in drug delivery. The available amphiphilic molecules that have been in practice for drug delivery application face issues like high cost, stability, and compatibility, thus there is a need to synthesize efficient amphiphiles from renewable resources. This project was designed to synthesize amphiphiles with diverse lipophilicity from naturally occurring flavonoid. Quercetin was selected as a polar head of amphiphile and was successfully derivatized with dodecyl bromide where the alkyl chain regio-selectively attached with different positions of quercetin hydroxyl (OH) groups. These compounds were characterized by MALDI, 1H NMR, 13C NMR, HMBC, and FTIR. Thin film hydration method was used for the synthesis of vesicles having their diameter in nano-ranges (300–400 nm). Amphotericin B was used as a host drug and the amphiphiles were able to entrap more than 90% drug. The nano-formulation was further analyzed by FTIR, UV–visible spectroscopy, DLS, and AFM to assess their stability, homogeneity, surface charge, CMC, and morphology. This analysis suggested that the amphiphiles are efficient for encapsulating the drug with good stability of the suspension. The drug loaded self-assembled nanostructures were administrated orally in rabbits to check oral bioavailability of amphotericin B. Results confirmed that the drug loaded self-assembled novel amphiphile baased vesicles enhanced oral bioavailability of the hydrophobic drug.

Influence of ligand and impurities on optical properties of carbon dots: Narrow linewidth and controllable UV-Vis spectrum

Optical properties of carbon molecules have been investigated with DFT. First, the results show that the wavelength of UV-Vis spectrum can be controlled by the number and the position of hydroxyl groups, while FWHM are only influenced by the position of hydroxyl groups. Second, study of molecules with different ligands (–Br, –OH, –COOH, –NH2) have confirmed that larger ligands would make the peaks wavelength of UV-Vis spectrum shift to red and make FWHM broaden. Finally, the doping of sulfur impurity would make the peaks wavelength of UV-Vis spectrum shift to longer wavelength than those doped with boron and nitrogen impurities.

Hydroxynorketamines: Pharmacology and Potential Therapeutic Applications.

Hydroxynorketamines (HNKs) are formed in vivo after (R,S)-ketamine (ketamine) administration. The 12 HNK stereoisomers are distinguished by the position of cyclohexyl ring hydroxylation (at the 4, 5, or 6 position) and their unique stereochemistry at two stereocenters. Although HNKs were initially classified as inactive metabolites because of their lack of anesthetic effects, more recent studies have begun to reveal their biologic activities. In particular, (2R,6R)- and (2S 6)-HNK exert antidepressant-relevant behavioral and physiologic effects in preclinical models, which led to a rapid increase in studies seeking to clarify the mechanisms by which HNKs exert their pharmacological effects. To date, the majority of HNK research has focused on the actions of (2R,6R)-HNK because of its robust behavioral actions in tests of antidepressant effectiveness and its limited adverse effects. This review describes HNK pharmacokinetics and pharmacodynamics, as well as the putative cellular, molecular, and synaptic mechanisms thought to underlie their behavioral effects, both following their metabolism from ketamine and after direct administration in preclinical studies. Converging preclinical evidence indicates that HNKs modulate glutamatergic neurotransmission and downstream signaling pathways in several brain regions, including the hippocampus and prefrontal cortex. Effects on other neurotransmitter systems, as well as possible effects on neurotrophic and inflammatory processes, and energy metabolism, are also discussed. Additionally, the behavioral effects of HNKs and possible therapeutic applications are described, including the treatment of unipolar and bipolar depression, post-traumatic stress disorder, chronic pain, neuroinflammation, and other anti-inflammatory and analgesic uses. SIGNIFICANCE STATEMENT: Preclinical studies indicate that hydroxynorketamines (HNKs) exert antidepressant-relevant behavioral actions and may also have analgesic, anti-inflammatory, and other physiological effects that are relevant for the treatment of a variety of human diseases. This review details the pharmacokinetics and pharmacodynamics of the HNKs, as well as their behavioral actions, putative mechanisms of action, and potential therapeutic applications.

The expression and purification of human steroid hormone processing enzyme CYP7B1 and the characterization of its interactive network

The cytochrome P450 monooxygenase CYP7B1 is an integral membrane protein at the endoplasmic reticulum (ER) membrane and catalyzes the hydroxylation of 7-alpha position of the steroid backbone, generating a series of important steroids such as 7α-hydroxy dehydroepiandrosterone and 7α-hydroxy pregnenolone. The disruption of CYP7B1 function could lead to abnormal oxysterols levels in neurons and the liver, and thus result in diseases such as hereditary spastic paraplegia and congenital bile acid synthesis defect. CYP7B1 was found to play a critical role in the biochemical network for biosynthesis/modification of steroids which involves hydrogenation/dehydrogenation, hydroxylation, oxygenation reaction at various carbon positions of the steroid backbone. Although a biologically-related enzyme, CYP7A1, has been successfully purified and structurally characterized, little was known about the structure and catalyzing mechanism for CYP7B1. To understand the structural basis of CYP7B1 functions, recombinant expression systems were screened for high-level expression and purification. Humans CYP7B1 was successfully expressed in the baculovirus/insect cell system and purified with its redox cofactor, indicating a natural folding for CYP7B1 samples. When challenged with detergents of various lengths of hydrophobic side chains, purified CYP7B1 proteins showed moderate stability but failed to maintain the natural folding upon the “harsh” detergent such as octyl glucoside. To explore the interactive proteins for CYP7B1, a pulldown-mass spectrometry assay using purified CYP7B1 was conducted and identified multiple ER-resident enzymes including cytochrome P450 reductase CYPOR as interactive proteins for CYP7B1, as well as other redox enzymes such as cytochrome b5 reductase and cytochrome b5 family members, indicating the existence of a physical interactive network at ER compromising cytochrome P450 and b5 family members and their reductases. Further efforts were conducted to confirm molecular interaction from mass-spectral assay and the in vitro macromolecular interaction assay showed the association between CYP7B1 and CYPOR. The CYP7B1-CYPOR protein complex was purified upon the optimization of co-expression system and in vitro assembly protocols, implying a catalytic complex might exist in ER membrane comprising CYP7B1, CYPOR, and other redox enzymes. Our results showed that human cytochrome P450 protein CYP7B1 could be purified in its cofactor-bound form and bind to cytochrome P450 reductase CYPOR to form a stable complex resistant to solubilization by detergent. Further studies should be conducted to map the components and interactions in the redox-enzyme complex at ER and determine the structural basis for the electron transfer therein.

Development of novel pH-sensitive azo dyes from Cardanol as a bioresource

PurposeThe purpose of this paper is to use the bio-based resource as the starting material for the synthesis of azo dye. Cardanol is one of the most used bio-based resources for carrying out the synthesis of various compounds having numerous end applications. The study presents an attempt to develop an azo dye from Cardanol having end applications in pH-responsive dyes.Design/methodology/approachThe cardanol was sulfonated to block the para position by which ortho positioned hydroxyl group after diazotization and coupling will provide necessary pH-sensitivity. The diazotization of two naphthalene derivatives, i.e. 1-naphthol-8-amino-3,6-disulfonic acid (H-acid) and 7-amino-4-hydroxy-2-naphthalene sulfonic acid (J-acid) was carried out using the standard practice, and the diazotized compounds were coupled with the sulfonated cardanol. The obtained dyes were characterized by Fourier transform infrared, nuclear magnetic resonance, carbon-hydrogen-nitrogen-sulfur analysis and hydroxyl value. The colour properties were checked using UV-vis spectrophotometry and density functional theory, while thermogravimetric analysis was used for the thermal degradation studies of both the dyes.FindingsWater-soluble cardanol-based azo dyes were prepared successfully having good thermal stability, and the obtained results are being presented in this paper.Originality/valueThe originality lies between the use of cardanol as a bio-based resource for the synthesis of azo-dye and the obtained azo-dye has the pH-sensitivity.

The construction of a new deep eutectic solvents system based on choline chloride and butanediol: The influence of the hydroxyl position of butanediol on the structure of deep eutectic solvent and supercapacitor performance

The precise regulation of the deep eutectic solvents (DESs) system has an important influence on its structure, performance and application. In this work, choline chloride (ChCl) and three kinds of butanediols are used as hydrogen bond acceptors and donors, respectively. The research focuses on the influence of two hydroxyl positions in butanediols on the structure and properties of DES systems with various characterization techniques. The results show that the DES system composed of 1, 2-butanediol and ChCl (the distance of two hydroxyl group is closest) possesses the largest conductivity (1.26 mS cm−1) and the lowest viscosity (56.99 cP). Moreover, using ChCl and 1, 2-butanediol as the electrolyte, the corresponding voltage of activated carbon (AC) based supercapacitor can reach 2 V, the specific capacitance can reach 116 F g−1 and the highest energy density is 16.14 Wh kg−1. More importantly, this work uses the DFT model to design and verify the DES systems in detail, and then explain the mechanism of the influence of the hydroxyl position on the structure and electrochemical performance of the DES system from a theoretical perspective. Obviously, the DES systems having difference structures and DFT calculation proposed in this article provide a significant way and reference for in-depth understanding of DES electrolytes and applications.

Insight into the effects of hydroxyl groups on the rates and pathways of tetracycline antibiotics degradation in the carbon black activated peroxydisulfate oxidation process

To investigate the effects of hydroxyl groups on the degradation of tetracycline antibiotics (TCs), three kinds of TCs [tetracycline (TC), oxytetracycline (OTC), and doxycycline (DTC)] were chosen as the target molecules and then degraded in the carbon black (CB)-activated peroxydisulfate (PDS) oxidation process. The degradation ratios of the TC, OTC, and DTC in the CB/PDS oxidation process reached 52%, 60%, and 87% within 40 min, respectively, with the degradation rate following the order of DTC > OTC > TC. According to the density functional theory calculations, these three TCs have different charge distributions, electrostatic potential distributions and average local ionization energy, which are caused by the distinct hydroxyl group position, thus contribute to the different degradation ratios and reaction rate constants. The hydrogenation of TC was slower special degradation pathway relative to those of OTC and DTC, while the decarbonylation of OTC was slower special degradation pathway relative to that of DTC, which adversely resulted in the degradation rate following the order of DTC > OTC > TC. This presentation gives a knowledge that the position and numbers of hydroxyl groups are pivotal to the degradation efficiency toward TCs.

Unraveling the interaction mechanism between collagen and alcohols with different chain lengths and hydroxyl positions

The present study systematically investigated the effects of alcohols, including methanol, ethanol, n-butanol, and propanol with different hydroxyl group numbers and locations on the thermal stability and molecular aggregation behavior of collagen. The results of ultra-sensitive differential scanning calorimetry (US-DSC), dynamic light scattering (DLS) and intrinsic fluorescence showed that with the increase of carbon chain length, alcohols can denature collagen, accompanied by transition in triple helical structure, promoted aggregation behavior, and altered molecular interactions. However, with the number of hydroxyl groups in alcohol molecules increased, the thermal stability of collagen increased and the molecules tended to disperse. Furthermore, radial distribution function (RDF) results showed that alcohols can change the structure of the hydration layer around collagen, thus altering the aggregation morphology of collagen molecules in solution. The results of the interaction between components in different alcohol systems demonstrated that with the decrease of alcohol polarity, bridge bond networks were formed between collagen molecules. Specifically, it was found that because the hydroxyl groups in 1,3-propanediol are located at both ends of the carbon chain, the reticular bridge bond structure formed between the collagen molecules changed into chain-like bridge structure. The bridge bonds between collagen molecules were considered to be weak cross-linking, which was an important reason for the destruction of collagen structure. In this study, the mechanism of interaction between different alcohols and collagen was elucidated, which will be helpful for further development of complex alcohol and collagen products.

Determination of substituent effects on the proton affinities of natural nucleosides by the kinetic method.

The kinetics of the unimolecular dissociations of proton-bound dimers produced by fast-atom bombardment from nucleosides and reference amines enables the evaluation of the proton affinities (PAs) of ribonucleosides. The PAs of cytosine, guanosine, adenosine, uridine, and deoxyuridine have been thus determined. These values and those already available for the corresponding DNA homologues allow the evaluation of the effect of the hydroxyl group in position 2' of the sugar moiety, which lowers the PAs of RNA nucleosides by 0.6-1 kcal/mol, and of the methyl group in position 5 of the thymine ring, which enhances the basicity of deoxythymidine over deoxyuridine by 0.6 kcal/mol.

Encapsulation of lipophilic polyphenols in plant-based nanoemulsions: impact of carrier oil on lipid digestion and curcumin, resveratrol and quercetin bioaccessibility.

Lipophilic polyphenol compounds (LPCs) are claimed to exhibit a broad spectrum of biological activities that may improve human health and wellbeing, including antioxidant, anti-inflammatory, and anti-cancer properties. Nanoemulsion-based delivery systems have been developed to encapsulate LPCs so as to increase their food matrix compatibility, physicochemical stability, and bioavailability. LPCs vary in their structural features, including the number and position of phenolic hydroxyl, ketone, and aliphatic groups, which results in different molecular, physicochemical, and gastrointestinal properties. In this study, we examined the impact of plant-based carrier oils (coconut, sunflower, and flaxseed oils) and LPC type (curcumin, resveratrol, and quercetin) on the in vitro gastrointestinal fate of polyphenols loaded into quillaja saponin-stabilized nanoemulsions. Coconut oil contains high levels of medium-chain saturated fatty acids (MC-SFAs), sunflower oil contains high levels of long-chain monounsaturated fatty acids (LC-MUFAs), and flaxseed oil contains high levels of long-chain polyunsaturated fatty acids (LC-PUFAs). The encapsulation efficiency and gastrointestinal stability of the LPCs were slightly lower in the MC than the LC oils. Differences in the gastrointestinal stability of the three LPCs were linked to differences in their oil-water partition coefficients. Some of the LPCs inhibited lipid digestion for certain oil types. In particular, resveratrol retarded the digestion of all three oils, but it still had the highest GIT stability and bioaccessibility. This study provides valuable information about the gastrointestinal fate of LPC-loaded nanoemulsions and highlights important differences in the behavior of LPCs with different characteristics. This knowledge may facilitate the design of more effective plant-based delivery systems for bioactive lipophilic polyphenols.