A New Cyclopropyl‐Triterpenoid from Ochradenus arabicus

One new cyclopropyl‐triterpenoid ( 1 ), along with four known constituents including octacosan‐1‐ol ( 2 ), pentacosanoic acid ( 3 ), β‐sitosterol ( 4 ), and β‐sitosterol 3‐O‐β‐D ‐glucopyranoside ( 5 ) were isolated from the aerial parts of Ochradenus arabicus for the first time. These compounds were isolated by repeated column chromatography followed by further purification through recycling HPLC. The structure of the new secondary metabolite 1 was established on the basis of UV, IR, 1D‐ (¹H‐ and ¹³C‐) and 2D‐NMR (HMBC and HSQC), and MS spectral data. The molecular mass was determined by HR‐MS, and hence the molecular formula was deduced. The configurations of stereogenic centers in the molecule were assigned by NOESY experiments, along with biogenetic considerations. The structures of the known compounds were confirmed by comparison of their physical and spectroscopic data with those reported in literature.     

Production, Purification, and Characterization of Exoglucanase by Aspergillus fumigatus

Fungi are considered good producers of industrially valuable enzymes with higher enzymatic activities. Among these cellulases are group of extracellular enzymes commonly employed in many industries for the hydrolysis of cellulolytic material. Aspergillus fumigatus produced exoglucanase having high enzymatic activity (83 U/gds) during the solid-state fermentation of wheat straw under optimum physical and nutritional conditions. Maximum production was obtained after 72 h of fermentation, at 55 °C temperature, pH 5.5, 80 % moisture level, and 2 mL fungal inoculum. Production was further increased by the addition of fructose (0.3 %) as additional carbon source, peptone (0.4 %) as nitrogen source, Tween-80 (0.3 %) as surfactant, and ammonium sulfate (0.2 %) in media. Exoglucanase was 2.30-folds purified by adding 40 % ammonium sulfate with volumetric activity 95.4 U/gds and specific activity 14.74 U/mg. Further, it was 5.18-folds purified by gel filtration chromatography with volumetric activity 115.2 U/gds and specific activity 33.10 U/mg. Purified exoglucanase has maximum activity at 55 °C and pH 4.8 using 1 % Avicel aqueous solution as substrate. The K _m and V _max were 4.34 mM and 7.29 μM/min, respectively. Calcium, magnesium, and zinc ions have positive effect on exoglucanase activity.     

pH-responsive amphiphilic hybrid random-type copolymers of poly(acrylic acid) and poly(acrylate-POSS): synthesis by ATRP and self-assembly in aqueous solution

The synthesis and subsequent self-assembly of novel, random-type amphiphilic pH-responsive hybrid copolymers, having acrylic acid as pH-responsive hydrophilic and acrylate-polyhedral oligomeric silsesquioxane (POSS) as hydrophobic constituents are reported. The synthesis was carried out in two steps: first, t-butylacrylate and acrylate-POSS are copolymerized by ATRP, followed by the acid hydrolysis of t-butyl acrylate constituents of the synthesized poly(t-butylacrylate)-co-poly(acrylate-POSS) copolymers to achieve poly(acrylic acid)-co-poly(acrylate-POSS). It was found that POSS is a powerful hydrophobic unit. With very low POSS concentration in the copolymers, i.e., one POSS unit per 40 to 110 acrylic acid repeat units, the obtained amphiphilic hybrid copolymers could self-assemble in aqueous solution to form nanoaggregates, as revealed by the laser light scattering and fluorescence studies on the aqueous solutions of the obtained copolymers. The formation of hydrophobic core in the self-assembled aggregates is verified by the solubilization of pyrene (used as probe in fluorescence measurements) in aqueous solution of the copolymers. In addition to pH-dependent self-assembly behavior, it is also demonstrated that the particle size and aggregation number of the aggregates can be tuned simply by varying the composition of the copolymer, i.e., by changing the molar ratio of poly(acrylic acid) to poly(acrylate-POSS) in the copolymer. Finally, preliminary results on the influence of salt (NaCl) on the self-assembly of poly(acrylic acid)-co-poly(acrylate-POSS) in aqueous solution are also presented.     

Synthesis and Antimicrobial Activity of N‐[(2Z)‐3‐(4,6‐Substitutedpyrimidin‐2‐yl)‐4‐phenyl‐1,3‐thiazol‐2(3H)‐ylidene]‐3, 5‐dinitrobenzamide Analogues

In this study, we have synthesized 1‐(4,6‐disubstitutedpyrimidin‐2‐yl)‐3‐(3,5‐dinitrobenzoyl)‐thiourea derivatives ( 1a , 1b , 1c , 1d , 1e , 1f , 1g , 1h ) and N‐[(2Z)‐3‐(4,6‐disubstitutedpyrimidin‐2‐yl)‐4‐phenyl‐1,3‐thiazol‐2(3H)‐ylidene]‐3, 5‐dinitrobenzamide ( 2a‐2h ) analogues and characterized by IR spectroscopy, NMR spectroscopy, elemental analysis, and single crystal X‐ray diffraction data. The compounds ( 2a‐2h ) were screened for antimicrobial activity against Gram positive, Gram negative, and fungal species. The results of antimicrobial study indicated that compounds showed most potential and appreciable antibacterial and antifungal activities.     

[Hydroxy(tosyloxy)iodo]benzene in Organic Synthesis: A Facile Synthesis of Furo[3,2-c]coumarins Using α-Tosyloxyketones

Facile synthesis of furo[3,2-c]coumarins (2a–g) via cyclocondensation of 4-hydroxycoumarin and α-tosyloxyketones (1a–g) is described. A plausible mechanism involving C-C bond formation followed by 5-exo-tet cyclization is suggested.     

Investigating a Class of Nonlinear Fractional Differential Equations and Its Hyers-Ulam Stability by Means of Topological Degree Theory

The aim of this article is to seek some adequate conditions via a prior estimate method (topological degree method) to derive the existence of solution to a nonlinear boundary value problem of fractional differential equations (FDEs). With the help of topological degree method which has been applied in many articles, we establish the required results for existence and uniqueness of solution to a class of FDEs. Moreover, we also formulate sufficient conditions for Hyers-Ulam stability to the solution of the considered problem. Finally, an appropriate example is provided to justify the relevant results.     

Structure elucidation of two new unusual monoterpene glycosides from Euphorbia decipiens, by 1D and 2D NMR experiments

Two new unusual monoterpene glycosides, (Z)-3,6-dimethyl-3-(β-D-O-glucosylmethylene)cyclohept-4-ene-1-one (1) and 3,6-dimethyl-3-(β-D-O-glucosylmethylene)cycloheptanone (2) have been isolated along with five known compounds, 3-hydroxy-4-methoxybenzoic acid, 6,7-dihydroxycoumarin, luteolin, apigenin 5-O-αl-L-rhamnoside, and pinocembrin-7-O-rutinoside from ethyl acetate extract of Euphorbia decipiens. The structures of the isolated compounds were elucidated by extensive 1D- and 2D-NMR, and mass spectroscopic analyses.     

Directed formation of DNA nanoarrays through orthogonal self-assembly

We describe the synthesis of terpyridine modified DNA strands which selectively form DNA nanotubes through orthogonal hydrogen bonding and metal complexation interactions. The short DNA strands are designed to self-assemble into long duplexes through a sticky-end approach. Addition of weakly binding metals such as Zn(II) and Ni(II) induces the formation of tubular arrays consisting of DNA bundles which are 50-200 nm wide and 2-50 nm high. TEM shows additional long distance ordering of the terpy-DNA complexes into fibers.     

Antioxidant and antimicrobial attributes and phenolics of different solvent extracts from leaves, flowers and bark of Gold Mohar [Delonix regia (Bojer ex Hook.) Raf

This paper describes the antioxidant and antimicrobial activities and phenolic components of different solvent (absolute methanol, absolute ethanol, absolute acetone, 80% methanol, 80% ethanol, 80% acetone and deionized water) extracts of leaves, flowers and bark of Gold Mohar [Delonix regia (Bojer ex Hook.) Raf.]. The extract yields from leaves, flowers and bark ranged from 10.19 to 36.24, 12.97 to 48.47 and 4.22 to 8.48 g/100 g dry weight (DW), respectively. Overall, 80% methanol extract produced from the leaves exhibited significantly (P < 0.05) higher antioxidant activity, with high phenolic contents (3.63 g GAE/100 g DW), total flavonoid contents (1.19 g CE/100 g DW), inhibition of peroxidation (85.54%), DPPH scavenging capacity (IC(50) value 8.89 μg/mL) and reducing power (1.87). Similarly, this 80% methanol leaves extract also showed superior antimicrobial activity. HPLC analysis of the 80% methanol extracts for individual phenolics revealed the presence of gallic, protocatechuic and salicylic acid in leaves; gallic, protocatechuic, salicylic, trans-cinnamic and chlorogenic acid in flowers, and gallic acid in bark as the main (amount > 1.50 mg/100 g DW) phenolic acids. Besides, small amounts ( < 1.50 mg/100 g DW) of some other phenolic acids such as sorbic, sinapic, p-coumaric, m-coumaric, ferulic, caffeic, 3-hydroxybenzoic, 4-hydroxycinnamic and 4-hydroxybenzoic acids were also detected. The extracts of the tested parts of Gold Mohar, especially, the leaves, might be valuable for functional food and therapeutic applications.     

Site specific interaction between ZnO nanoparticles and tryptophan: a first principles quantum mechanical study

First principles density functional theory calculations are performed on tryptophan-ZnO nanoparticles complex in order to study site specific interactions between tryptophan and ZnO. The calculated results find the salt bridge structure involving the -COOH group and ZnO cluster to be energetically more favorable than other interacting sites, such as indole and amine groups in tryptophan. The interaction between tryptophan and ZnO appears to be mediated by both ionic and hydrogen bonds. The calculated molecular orbital energy levels and charge distributions suggest non-radiative energy transfer from an excited state of tryptophan to states associated with ZnO, which may lead to a reduction in the emission intensity assigned to the π-π* transition of the indole functional group of tryptophan.