Identification and determination of flavonoids,carotenoids and chlorophyll concentration in Cynodon dactylon (L.) by HPLC analysis

Cynodon dactylon (L.) is a potent medicinal plant in the traditional and current Indian medicinal systems. The objective of this research was to find out the levels of flavonoids, carotenoids and chlorophyll b in C. dactylon leaves by high-performance liquid chromatography (HPLC) equipped with a diode array detector. HPLC analysis revealed that total carotenoid and total flavonoid concentration were 62 mg/100 g and 249.1 μg/g, respectively. The mean chlorophyll b was 85.1 mg/100 g in C. dactylon. Among the flavonoids, quercetin (164.7 μg/g) was the major flavonoid followed by kaempferol (48.2 μg/g), rutin (18.4 μg/g), catechin (12.1 μg/g) and myricetin (5.7 μg/g). Of the carotenoids, β-carotene (35.2 mg/100 g) was predominant followed by lutein (17.0 mg/100 g), violaxanthin (5.8 mg/100 g) and zeaxanthin (4.2 mg/100 g). Chlorophyll b concentration was 85.1 mg/100 g in C. dactylon. The results of this investigation should be useful information for further pharmacological studies.     

Continuum interpretation of virial stress in molecular simulations

The equivalence of the virial stress and Cauchy stress is reviewed using both theoretical arguments and numerical simulations. Using thermoelasticity problems as examples, we numerically demonstrate that virial stress is equivalent to the continuum Cauchy stress. Neglecting the velocity terms in the definition of virial stress as many authors have recently suggested, can cause significant errors in interpreting MD simulation results at elevated temperatures (T > 0 K).     

Schiff’s base phenol-hydrazone derivatives as colorimetric chemosensors for fluoride ions

Two new chromogenic receptors 4-nitro-2-[(phenylhydrazoimino)methyl]phenol (1) and 4-nitro-2-[(4-nitrophenylhydrazoimino)methyl]phenol (2) containing a nitro group as a signalling unit and OH and NH groups as binding sites have been synthesized and characterized by spectroscopic techniques and XRD. Both receptors show colorimetric responses and UV-vis spectral changes in the presence of fluoride ions in organic solvents.     

Synthesis and structural study of thiacyclophanes utilizing dibromides and methane dithiolate

The synthesis of a series of thiacyclophanes and optically active binaphthol-based chiral thiacyclophanes is reported with XRD structure. Two diastereomeric tetrathiacyclophanes are designed and synthesized. The two diastereomers are evidenced by crystal structure; the single-crystal X-ray studies reveal that one of the isomers possesses an inherent property of self-assembling into a vertical stack of tunnel-like structures.     

Quaternary ammonium hydroxide-functionalized g-C3N4 catalyst for aerobic hydroxylation of arylboronic acids to phenols

A new and efficient metal-free approach toward the synthesis of phenols via an aerobic hydroxylation of arylboronic acids by using a novel quaternary ammonium hydroxide g-C₃N₄ catalyst has been described. The functionalized quaternary ammonium hydroxide (g-C₃N₄-OH) has been prepared from graphitic carbon nitride (g-C₃N₄) scaffold by converting the residual –NH₂ and –NH groups to quaternary methyl ammonium iodide by performing a methylation reaction with methyl iodide followed by ion-exchange with 0.1 N KOH or anion exchange resin Amberlyst A26 (OH- form) by post-synthetic modification. The resultant g-C₃N₄-OH was characterized by XRD, FTIR, field-emission scanning electron microscope (FESEM), high-resolution transmission electron microscope (HRTEM), N₂ adsorption/desorption isotherms, and acid–base titration. Tested as solid-base catalysts, the g-C₃N₄-OH showed excellent catalytic activity in the aerobic hydroxylation reaction by converting a variety of arylboronic acids to the corresponding phenols in high yields. More importantly, the g-C₃N₄-OH solid-base has been successfully reused four times with the minor loss of initial catalytic activity (10.5%).     

Nickel‐Catalyzed Borylative Coupling of Alkynes,Enones, and Bis(pinacolato)diboron as a Route to Substituted Alkenyl Boronates

Three‐component coupling reactions of an alkyne, an enone, and a diboron reagent provide access to highly substituted alkenyl boronates in good to excellent yields (see scheme). The coupling is highly regio‐ and stereoselective, and the products are amenable to further functional‐group transformations. R¹,R²=H, alkyl, aryl, CO₂Me; R³=alkyl, Ph; R⁴,R⁵=H, alkyl.