Halide ion effect on the chloroform chemical shift in supramolecular complexation studies with tetra-n-butylammonium salts: a 1H NMR and X-ray study

A ¹H NMR spectroscopic study of tetra-n-butylammonium halides (TBAX: X = Cl^? , Br^?  or I^? ) in CDCl₃ solutions was conducted. Complexation studies of TBAX salts with different host molecules using ¹H NMR in CDCl₃ have previously revealed that the reference residual CHCl₃ proton signal had been shifted downfield. The aim of the study was to quantify the extent of these chemical shift changes with TBAX salts. Linear concentration–chemical shift relationships in each case were obtained from the resulting titration plots obtained from the addition of the TBAX salts alone to CDCl₃. Interactions in the solid state as determined by X-ray crystallography support the solution-state investigations indicating halide ion–chloroform proton interactions.     

Bioguided isolation of pentacyclic triterpenes from the leaves of Alstonia scholaris (Linn.) R. Br. growing in Egypt

Ethanolic and aqueous extracts of the leaves and flowers of Alstonia scholaris were evaluated for their antioxidant activity by investigating their effect on blood glutathione levels in alloxan-induced diabetic rats. The ethanolic extract of the leaves was the most active; therefore, its cytotoxicity against HepG2 cells was also tested. Promising GI?? values of 1.96, 4.34 and 4.65?μg?mL?1 were observed for the extract, its chloroform and ethyl acetate fractions, respectively. The chloroform active subfraction I (GI???=?2.97?μg?mL?1) yielded betulin (1), betulinic acid (2) and ursolic acid (3) upon purification. Compounds 1-3 were identified using spectroscopic techniques and by comparison with reported data. GLC of unsaponifiable and saponifiable fractions of the hexane extract revealed β-sitosterol (7.37%) and n-tetracosane (54.4%) to be the major sterol and hydrocarbon components, respectively. Linoleic acid (48.89%) was the predominant fatty acid.     

Molecular recognition of nucleobases and amino acids by sulphonato-calixnaphthalene-capped silver nanoparticles

The plasmon resonances of sulphonato-calixnaphthalene-capped silver nanoparticles have been used to study the complexation of the nanoparticles with nucleobases and amino acids. Only in the case of the nanoparticles capped with oxacalix[4]naphthalenesultone, does complexation of both nucleobases and certain amino acids occur. The complexation of the aromatic amino acids, phenylalanine and tryptophan, has previously not been observed for calixarene-capped silver nanoparticles.     

A new method for pH triggered curcumin release by applying poly(l-lysine) mediated nanoparticle-congregation

We introduce a novel method for encapsulation of curcumin by synthesizing microcapsule containing self-assembled nanoparticles using poly (l-lysine), trisodium citrate and silica sol. Such microcapsules can only be prepared in neutral and alkaline environment and unencapsulated curcumin can be effectively removed by simple centrifugation with encapsulation efficiency 57.34%. The particle sizes are in the range 0.7–3 μm with an effective diameter 1.05 μm. The structure of the microcapsules is dependent upon the solubility of curcumin in the solvent environment, the microcapsule are spherical when prepared in 10% acetone and bowl-shaped/conical when prepared in water suspension, however, the size of these curcumin encapsulated microcapsules remain similar. Fluorescence microscope images confirm that curcumin is predominantly concentrated within the shell wall of the capsules. Photophysical behavior of Micro-curcumin with respect to curcumin alone is evaluated. Release of curcumin is found to be triggered by pH where acidic environment trigger maximum release compared to basic and neutral conditions. Micro-curcumin is as stable as curcumin. Drug release efficiency is found to be 61.44% and the drug release profile of Micro-curcumin follow Higuchi model. It is also revealed that β-diketone group of curcumin responsible for scavenging activity is retained in the Micro-curcumin, thus suggesting applicability of such system as a poorly water soluble drug delivery vehicle. In contrast to other curcumin delivery systems, the presented method is easy, fast and does not need flow rate monitoring device. In addition poly (l-lysine) as a non-toxic and highly stable material that prevents metabolic degradation is used in the present preparation method.     

A sulphated flavone glycoside from Livistona australis and its antioxidant and cytotoxic activity

A new flavone glycoside tricin 7-O-β-glucopyranoside-2″-sulphate sodium salt along with 14 known flavonoid compounds were isolated and identified from the aqueous methanol extract of Livistona australis leaves. Their structures were established on the basis of extensive NMR (1H, 13C, HSQC and H-H COSY) and ESIMS data. Antioxidant and cytotoxicity properties of the methanol extract of the leaves as well as the new compound were investigated.     

Chemical and biological study of the seeds of Eragrostis tef (Zucc.) Trotter

A chemical study of the red type of the seeds of Eragrostis tef (Zucc.) Trotter (Poaceae) led to the isolation of seven compounds from its ethanol extract, namely β-sitosterol (1), β-amyrin-3-O-(2'-acetyl(glucoside (2), β-sitosterol-3-O-β-D-glucoside (3), naringenin (4), naringenin-4'-methoxy-7-O-α-L-rhamnoside (5), eriodictyol-3',7-dimethoxy-4'-O-β-D-glucoside (6) and isorhamnetin-3-O-rhamnoglucoside (7), which are reported for the first time in the genus Eragrostis. This is the first report for the isolation of compounds (2) and (6) in nature. The isolated compounds were identified using different spectroscopic methods (EIMS, UV, 1H NMR, 13C NMR, HMQC and HMBC). A proximate analysis revealed the high nutritive value of the seeds: carbohydrates (57.27%), protein (20.9%), essential amino acids (8.15%) with major leucine and lysine (1.71 and 1.35%, respectively), vitamin B? (1.56?mg/100?g) and potassium and calcium (32.4 and 9.63%, respectively). The seeds yielded 22% w/w of fixed oil rich in unsaturated fatty acids (72.46%), among which oleic acid, was predominant (32.41%), followed by linolenic acid (23.83%). The ethanolic extract and fixed oil of the seeds exhibited anti-hyperlipedaemic and anti-hyperglycaemic activities. Oral administration of the fixed oil for 10 days resulted in a rise in serum calcium levels in rats.     

Solvent Effects on the Structure-Property Relationship of Some Potentially Pharmacologically Active 3-(4-Substituted Benzyl)-5-Ethyl-5-Phenyl- and 3-(4-Substituted Benzyl)-5,5-Diphenylhydantoins

Two series of 3-(4-substituted benzyl)-5-ethyl-5-phenyl- and 3-(4-substituted benzyl)-5,5-diphenylhydantoins were synthesized and their UV absorption spectra were recorded in the region 200–400 nm in selected solvents of different polarity. The effects of solvent dipolarity/polarizability and solvent/solute hydrogen bonding interactions on the spectral shifts were analyzed by means of the linear solvation energy relationship (LSER) methodology of Kamlet and Taft. The quantitative relationships between hydrogen bonding interactions and the lipophilicity and blood-brain permeation of the studied compounds were discussed. Satisfactory linear dependences were obtained for moderate electron-donating and electron-withdrawing substituents at the benzyl moiety, while the strong electron-withdrawing substituent (NO₂) significantly modifies the solvation characteristics of the molecule. The paper clearly demonstrates how the solvatochromic comparison method may be applied to estimate the contributions of various modes of solvation to the pharmaceutically relevant properties of these newly synthetized hydantoin derivatives.