Targeted Synthesis of 3,3′-, 3,4′- and 3,6′-Phenylpropanoid Sucrose Esters

In this study, we report on an orthogonal strategy for the precise synthesis of 3,3′-, 3,4′-, and 3,6′-phenylpropanoid sucrose esters (PSEs). The strategy relies on carefully selected protecting groups and deprotecting agents, taking into consideration the reactivity of the four free hydroxyl groups of the key starting material: di-isopropylidene sucrose 2. The synthetic strategy is general, and potentially applies to the preparation of many natural and unnatural PSEs, especially those substituted at 3-, 3′-, 4′- and 6′-positions of PSEs.

Technological Aspects of Highly Selective Synthesis of Allyloxyalcohols—New, Greener, Productive Methods

Allyl ethers bearing free hydroxyl groups of CH2=CH-CH-O-A-OH type (hydroxyalkyl allyl ethers, allyloxyalcohols) are valuable chemicals in many environmentally friendly industrial applications. The development of technologically attractive methods for their production is necessary. The two pathways (L-L PTC and non-catalytic solvent-free conditions) were optimized for the highly selective and yield synthesis of 4-allyloxybutan-1-ol. Improvements in the PTC method (50% NaOH(aq), the equimolar ratio of NaOH to diol, cyclohexane as solvent) with a new highly selective and effective PT catalyst, i.e., Me(n-Oct)3N+Br− (0.3 mol%), resulted in 88% yield and 98% selectivity of 4-allyloxybutan-1-ol with minimal formation of allyl chloride hydrolysis by-products (<1%). In turn, application of non-catalytic solvent-free conditions and the change in the key substrate with an excess of diol and use of solid NaOH solely led to a mono-O-allylation product with an excellent yield of 99% in a relatively short reaction time (3.5 h), with trace amounts of by-products (<0.1%). This sustainable method is perfectly suitable for the synthesis on a larger scale (3 moles of the key substrate) and for the full O-allylation process.

Preparation of Electrospun Polyvinyl Alcohol/Nanocellulose Composite Film and Evaluation of Its Biomedical Performance

Using polyvinyl alcohol (PVA) and nanocellulose (NC) as raw materials, PVA/NC nanofiber membranes were prepared by electrospinning. The hydrogen bonding, crystalline properties and microscopic appearance of PVA/NC membranes with different NC contents were characterized. The mechanical properties, liquid absorption and cytotoxicity of the nanofiber membrane were evaluated. The results show that the free hydroxyl group of the PVA/NC nanofiber membranes have a maximum value of 9% at a mass fraction of 6% NC. The crystallinity of the PVA/NC nanofiber membranes and the average diameter of the nanofibers decreased and then increased as the NC content increased, with a minimum value of 38.23% and 272.03 nm, respectively, at 6% NC content. At this time, the contact angle was the smallest. The maximum strength of the PVA/NC nanofiber membranes is 75.8% higher than that of the PVA membrane at 2% NC content. With increasing NC content, the absorption of water, PBS sustained-release suspensions and artificial blood by PVA/NC nanofiber membranes increases. Cytotoxicity tests have shown that PVA/NC nanofiber membranes are non-toxic, have good cytocompatibility and are expected to be used in the field of medical dressings.

Structural Modification of the Macrolide Brefeldin A to Analogues with Enhanced Cytotoxicity against KB Cells

The macrolide brefeldin A (BFA, 1) exhibited high cytotoxicity against KB cells. However, it was also toxic against non-cancerous cells. In order to lower toxicity against normal cells while maintaining the cytotoxic potency to the cancer cells, structural modification of this compound was undertaken. Starting from compound 1, the analogues 2-13 were synthesized and evaluated for cytotoxicity against KB cells. The analogue 2 exhibited the most potent cytotoxicity against KB cells, with an IC50 value of 0.034 nM, 67-fold more active than its parent compound 1. It was 41764 and 8235 fold more active than the standard drugs ellipticine and doxorubicin, respectively. The higher cytotoxicity against KB cells and lower toxicity against Vero cells of analogue 2 than those of the parent compound 1 contributed to its exceptionally high selectivity index of 9117. The results suggested that this analogue might be utilized to develop a new candidate for an anticancer drug. HIGHLIGHTS Oral cancer is a major worldwide public health issue and may affect any oral cavity region, including the lips, tongue, mouth and throat The ester analogues (2-13) were the first report of the cytotoxic against human epidermoid carcinoma (KB) cells 7-O-acetyl BFA (2) exhibited the most potent cytotoxicity against KB cells, with an IC50 value of 034 nM, 67-fold more active than its parent compound 1 The essentially structural features for the macrolide of BFA-type to exhibit high cytotoxicity against KB cells are the presence of a free hydroxyl group at the 4-position, a free hydroxyl group or the corresponding ester at the 7-position, and unsaturated functions at the 2- and 10-positions GRAPHICAL ABSTRACT

Aging Resistance of Biocomposites Crosslinked with Silica and Quercetin

This research focuses on revealing the double role of quercetin accompanied by silica in epoxidized natural rubber. A crosslinking ability with antioxidative properties exists and reveals the dependence of these functions on quercetin content. Here, the aging resistance of self-healable biocomposites was analyzed. The self-healing properties were presented in our previous work. The stabilizing effect of quercetin applied as a crosslinking agent has been studied in epoxidized natural rubber with a 50 mol% of epoxidation (ENR-50). Some of five -OH moiety groups existing in the quercetin structure are able to react with epoxy rings of ENR-50 and cure this elastomer, whereas other free hydroxyl groups can donate the hydrogen molecule to a radical molecule, stabilizing it. The aging resistance of prepared composites was estimated by mechanical tests conducted before and after different types of aging, as well as by differences in color and surface energy between aged and un-aged samples. Changes within the oxygen function, which occurred as a result of the aging process, were observed using FT-IR absorbance spectroscopy. Furthermore, the impact of quercetin content on composites’ thermal stability was investigated by thermogravimetry (TGA). According to the results, a proper dose of quercetin can act as a crosslinker and antioxidant in ENR-50 at the same time.

Removal of cephalexin from aqueous solutions using the fenton photocatalytic process

This paper aims to study the degradation and oxidation/mineralization process of cephalexin in model systems using Fenton’s reagent for UV irradiation (λ = 254 nm). The effect of pH (2-11), concentration of H2O2 (0,3434 mg/L) and concentration of Fe(II) (0-28 mg/L) on the degradation of 50 mg/L CPX were investigated. It has been determined optimum conditions for photocatalytic oxidation of CPX. Increasing the amount of H2O2 plays an inhibitory role in the production of hydroxyl radicals and reduces the process efficiency. This can be attributed to the reaction of excess peroxide with •OH and the formation of HO2 •, which has less oxidizing power compared to free hydroxyl radical. And as the concentration of the catalyst increases to the optimum, the excess of Fe(II) ions reacts with the hydroxyl radical and, therefore, the efficiency of the process also is reduced. Accordingly, the optimum degradation efficiency of 88 % and 83% for COD was obtained under the following conditions: pH 2,5, H2O2 concentration – 3,4 mg/L, Fe(II) ions concentration – 5,6 mg/L, cephalexin concentration – 50 mg/L, and reaction time – 60 min. Thus, the current study demonstrated that the photo-Fenton reactor can be used effectively as an advanced oxidation treatment unit for degradation of cephalexin under optimized environmental conditions.

Fluorescent Composite Hydrogel of Carboxymethyl Celluose-Eu(Ⅲ)/Polyvinyl Alcohol and Its Application in Functional Paper

A novel carboxymethyl cellulose-Europium(Ⅲ)/polyvinyl alcohol (CMC-Eu(Ⅲ)/PVA) fluorescent hydrogel was prepared by a green and facile method. The hydrogel formed a physical cross-linking network under mild reaction conditions without using volatile organic chemical reagents. A porous structure was formed by the hydrogen bonding and other interaction between the PVA chains and the free hydroxyl on CMC-Eu(Ⅲ) during the composite gel transformation process. The addition of CMC-Eu(Ⅲ) improved the tensile and compressive mechanical properties of PVA hydrogel. When the CMC-Eu(Ⅲ) content was 15%, the maximum tensile stress of the composite hydrogel was 47.25±10.35 kPa and the compressive stress was 10.14±1.90 kPa. Meanwhile, the CMC-Eu(Ⅲ)/PVA hydrogels exhibited a 5D0→7F2 characteristic emission peak of Eu3+ at 615 nm, and emitted stable red fluorescence under UV irradiation at 254 nm. Moreover, the hydrogel was applied in making fluorescent paper as an internal sizing agent. When the amount of hydrogel was 1%, the tensile strength of fluorescent paper reached 3.52 kN/m, which is promising in the application of anti-counterfeiting.

Bioactivity of Some Natural and Semisynthetic Coumarin Derived Compounds

A couple of natural coumarins was identified in the seeds of two apples’ cultivars commonly known as Granny Smith and Red Delicious. The effect of the phenolic hydroxyl moieties found in these products was evaluated on the bioactivity. This evaluation included the structural alteration of these moieties into less hydrophilic ones to explore the significance of the parent moieties on the biological activity. The investigated biopotentials were antioxidant, antiproliferative, antibacterial, and antifungal effects. The antioxidant potential was investigated by detecting the ability of the natural and semisynthetic coumarins to trap the free hydroxyl and DPPH radicals. The antiproliferative potential was assessed via an MTT-depended assay versus eight cancerous-cell lines, included HeLa, SK-OV-3, AR42J, MCF-7, AB12, KYSE-30, LC540, and AMN3. The antibacterial potential was tested versus six common pathogenic bacterial strains via a well-defined disc diffusion assay. These pathogens were Escherichia coli, Salmonella typhi, Klebsiella pneumonia, Haemophilus influenzae, Shigella dysenteriae, and Pseudomonas aeruginosa. The antifungal potential was also screened by utilizing a similar microbiological technique versus three pathogenic fungi, involved Candida albicans, Aspergillus flavus, and Aspergillus niger. It is concluded that the investigated chemical moiety has a positive influence on the antioxidant and antiproliferative potentials of the natural derivatives, and a negative one on their antibacterial and antifungal potentials.

Theoretical Study of Hydrogen Bond Formation in Four Rare Sugars: Gulose, Allose, Altrose, and Talose

Rare sugars are monosaccharides with tremendous potential for applications in pharmaceutical, cosmetics, nutraceutical, and flavors industries. The four rare sugars, including; gulose, allose, altrose and talose are stereoisomers that are different in the hydroxyl group orientation (axial or equatorial) on the C2-4 atoms. The DFT, AIM, and, NBO calculations were used to probe the probability of formation of internal H-bonds in four rare sugars. The AIM analysis identified that altrose and talose can form three predominantly intramolecular H-bonds, whereas gulose and allose revealed one and two H-bonds, respectively and these normal intramolecular H-bonds are mostly closed-shell interactions. The theoretical calculated O-H stretching FT-IR vibrational frequencies confirmed that the intramolecular H-bonds shifted toward low frequencies in comparison to the free hydroxyl group, which caused the red-shift. Also, the lowest IR frequency in each sugar was related to the structure with the highest stabilization energy and the most strongest intramolecular H-bonds.