Carbon dioxide mediated stereoselective copper-catalyzed reductive coupling of alkynes and thiols

A simple protocol for the stereoselective copper-catalyzed hydrothiolation of alkynes under a CO(2) atmosphere has been developed. The stereoselectivity is determined by the presence/absence of a CO(2) atmosphere. The reaction system is robust and utilizes inexpensive, readily available substrates. A cyclic alkene/carboxylate copper complex intermediate is proposed as the key step in determining the stereoselectivity, and an equivalent amount of water is found to play an active role as a proton donor.     

Using an electrical potential to reversibly switch surfaces between two states for dynamically controlling cell adhesion

Smart surfaces presenting both antifouling molecules with a charged functional group at their distal end, and molecules that are terminated by RGD peptides for cell adhesion, were fabricated and characterized (see picture). By applying potentials of +300 or -300?mV, the surfaces could be dynamically switched to make the peptide accessible or inaccessible to cells.     

Correlation of crack patterns and ring bands in spherulites of low molecular weight poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactic acid)

Only a single type of circular circumferential crack is conventionally reported for poly(l-lactic acid) (PLLA). In this study, PLLA samples were found to exhibit as many as four crack types of different directions and patterns, which cannot be feasibly explained simply by the directional difference in coefficients of thermal expansion. Depending on crystallization temperature (T _c), PLLA crystallizes into ringless or ring-banded spherulites, whereas the crack patterns are dramatically different in these two types of spherulites. In ring-banded spherulites of PLLA crystallized at intermediate T _c, two uniquely different crack types are present: (1) twin circumferential cracks coinciding with the dark–bright and bright–dark boundary and (2) radial short-segmental voids coinciding on the bright bands in spherulites. The radial short-segmental cracks on the bright band of ring-banded spherulites may be caused by PLLA crystals of radial direction with various twisting that contract laterally upon cooling. Only circumferential cracks are present in PLLA crystallized into ringless spherulites, where concentric continuous circumferential cracks are present in the ringless spherulites at low T _c with finer lamellae, but discontinuous and irregular circumferential cracks are present in the ringless spherulites at high T _c with coarse lamellae. Although all cracks are triggered by cooling from T _c, all evidences indicate that the crack patterns and types are highly associated with the lamellar orientation, patterns, and coarseness in spherulites.     

Honey: a novel antioxidant

The global prevalence of chronic diseases such as diabetes mellitus, hypertension, atherosclerosis, cancer and Alzheimer's disease is on the rise. These diseases, which constitute the major causes of death globally, are associated with oxidative stress. Oxidative stress is defined as an "imbalance between oxidants and antioxidants in favor of the oxidants, potentially leading to damage". Individuals with chronic diseases are more susceptible to oxidative stress and damage because they have elevated levels of oxidants and/or reduced antioxidants. This, therefore, necessitates supplementation with antioxidants so as to delay, prevent or remove oxidative damage. Honey is a natural substance with many medicinal effects such as antibacterial, hepatoprotective, hypoglycemic, reproductive, antihypertensive and antioxidant effects. This review presents findings that indicate honey may ameliorate oxidative stress in the gastrointestinal tract (GIT), liver, pancreas, kidney, reproductive organs and plasma/serum. Besides, the review highlights data that demonstrate the synergistic antioxidant effect of honey and antidiabetic drugs in the pancreas, kidney and serum of diabetic rats. These data suggest that honey, administered alone or in combination with conventional therapy, might be a novel antioxidant in the management of chronic diseases commonly associated with oxidative stress. In view of the fact that the majority of these data emanate from animal studies, there is an urgent need to investigate this antioxidant effect of honey in human subjects with chronic or degenerative diseases.     

Fructose might contribute to the hypoglycemic effect of honey

Honey is a natural substance with many medicinal properties, including antibacterial, hepatoprotective, hypoglycemic, antioxidant and antihypertensive effects. It reduces hyperglycemia in diabetic rats and humans. However, the mechanism(s) of its hypoglycemic effect remain(s) unknown. Honey comprises many constituents, making it difficult to ascertain which component(s) contribute(s) to its hypoglycemic effect. Nevertheless, available evidence indicates that honey consists of predominantly fructose and glucose. The objective of this review is to summarize findings which indicate that fructose exerts a hypoglycemic effect. The data show that glucose and fructose exert a synergistic effect in the gastrointestinal tract and pancreas. This synergistic effect might enhance intestinal fructose absorption and/or stimulate insulin secretion. The results indicate that fructose enhances hepatic glucose uptake and glycogen synthesis and storage via activation of hepatic glucokinase and glycogen synthase, respectively. The data also demonstrate the beneficial effects of fructose on glycemic control, glucose- and appetite-regulating hormones, body weight, food intake, oxidation of carbohydrate and energy expenditure. In view of the similarities of these effects of fructose with those of honey, the evidence may support the role of fructose in honey in mediating the hypoglycemic effect of honey.     

ZnO nanoparticles and poly(acrylic) acid-based polymer gel electrolyte for photo electrochemical cell

This work presents a photo electrochemical cell based on zinc oxide (ZnO) nanoparticles and poly(acrylic) acid (PAA) doped with sodium iodide (NaI) and iodine (I₂) polymer gel electrolyte. The ZnO powders were synthesized by sol–gel storage and sol–gel centrifugation. The ZnO powder synthesized via sol–gel centrifugation showed the optimal structural properties, with largest crystallite sizes of 58 nm, average particles size between 20 and 80 nm and indirect band gap energy of 3.20 eV. The highest conductivity [(8.0 ± 0.1) × 10^?2 S cm^?1] was obtained for PAA + 0.8 M NaI + 0.02 M I₂. This sample achieved the lowest activation energy (0.029 eV) and electrochemical stability at 1.6 V. The ZnO powder synthesized via sol–gel centrifugation and PAA + 0.8 M NaI + 0.02 M I₂ was fabricated as a Cu–ZnO/PAA + 0.8 M NaI + 0.02 M I₂/C-ITO photo electrochemical cell.     

Molecular imprinted polymer for β-carotene for application in palm oil mill effluent treatment

Palm oil mill effluent (POME) is one of the most significant pollutant in the form of wastewater. It could have negative effects on the environment include the emission of biogas and water pollution which comes from discharging the brownish tick POME to the water bodies if not properly managed. Discharge of dark brownish colored of POME directly into water bodies may affect the aquatic life as it will reduce sunlight penetration and suppress the photosynthetic activity. A molecularly imprinted polymer (MIP) for removal of β-carotene from POME has been aimed to develope in this study. The preparation of β-carotene imprinted and non-imprinted polymer (NIP) involves polymerization of β-carotene (or without it) with β-cyclodextrin (β-CD), 9-vinylcarbazole (9VC), tolylene diisocyanate (TDI) and N,N-dimethylformamide (DMF) as the monomer, co-monomer, cross-linker and solvent (porogen), respectively. Analysis from FTIR showed that MIP and NIP have similar characteristic peak with different peaks intensity, indicating the similarity in the backbone structure of polymerization. TGA result displayed high thermal stability with final decomposition at 320 °C for MIP-β-CD-9VC as compared to NIP-β-CD-9VC. The pH study shows that sorption of β-carotene increased with decreasing the pH of POME and the maximum sorption capacities achieved at pH 2 were 10 μg/g and 7 μg/g for MIP-β-CD-9VC and NIP-β-CD-9VC, respectively. The maximum sorption achieved by using 500 mg of MIP as the sorption of β-carotene increased with increasing the dosage of MIP. Kinetic model evaluation has been applied on this prepared materials. The sorption equilibrium data was well described by Freundlich model. The results indicated that the sorption of β-carotene on MIP follows a pseudo–second–order kinetic.     

Acetyl- and O-alkyl- derivatives of β-mangostin from Garcinia mangostana and their anti-inflammatory activities

Pure β-mangostin (1) was isolated from the stem bark of Garcinia mangostana L. One monoacetate (2) and five O-alkylated β-mangostin derivatives (3–7) were synthesised from β-mangostin. The structures of these compounds were elucidated and determined using spectroscopic techniques such as 1D NMR and MS. The cytotoxicities and anti-inflammatory activities of these five compounds against RAW cell 264.7 were tested. The structural-activity relationship studies indicated that β-mangostin showed a significant activity against the LPS-induced RAW cell 264.7, while the acetyl- as well as the O-alkyl- β-mangostin derivatives did not give good activity. Naturally occurring β-mangostin demonstrated comparatively better anti-inflammatory activity than its synthetic counterparts.