Synthesis and antimicrobial studies of hydroxylated chalcone derivatives with variable chain length

A series of (E)-1-(4-alkyloxyphenyl)-3-(hydroxyphenyl)-prop-2-en-1-one have been successfully synthesised via Claisen-Schmidt condensation. The synthesised chalcone derivatives consisted of hydroxyl groups at either ortho, meta or para position and differed in the length of the alkyl groups, C (n) H(2) (n) (+1,) where n?=?6, 10, 12 and 14. The structures of all compounds were defined by elemental analysis, IR, (1)H- and (13)C-NMR. The antimicrobial studies were carried out against wild-type Escherichia coli American Type Culture Collection 8739 to evaluate the effect of the hydroxyl and the alkyl groups of the synthesised chalcones. All the synthesised compounds have shown significant antimicrobial activities. The optimum inhibition was dependent on the position of the hydroxyl group as well as the length of the alkyl chains.     

Antitumour compounds from a saline soil isolate, Streptomyces griseoincarnatus CTF15

A new actinomycete strain designated as Streptomyces sp. CTF15 was isolated from a saline soil using casein-KNO(3) agar medium. The strain Streptomyces sp. CTF15 exhibited promising antimicrobial activity against Staphylococcus aureus, Bacillus subtilis, Streptomyces viridochromogens Tu57 and high cytotoxicity (91.2% mortality) against Artimia salina in biological screening. The cultivation of this strain in a 50 L lab fermenter and subsequent isolation and purification by a series of chromatographic techniques and structure elucidation by MS and NMR analysis of the active metabolites revealed that it is a highly stable producer of resistomycin (1), tetracenomycin D (2) and actinomycin D (3), even under non-optimised culture conditions. The morphological, microscopic, biochemical and physiological characterisation suggested that the strain CTF15 belongs to the genus Streptomyces. A partial 16S rRNA gene sequence (1429 bp) from the strain CTF15 was determined and found to have high identity (99%) with Streptomyces griseoincarnatus. As such, this is the first report of a strain of S. griseoincarnatus capable of producing these three bioactive compounds simultaneously.     

Bis-Thiourea Bearing Aryl and Amino Acids Side Chains and Their Antibacterial Activities

Abstract

A series of symmetrical 1,3-bis thiourea 1a–e and 1,4-bis thiourea derivatives 2a–e have been successfully synthesized from the reactions of amines with 3-acetylbenzoyl isothiocyanate and 4-acetylbenzoyl isothiocyanate, respectively. All the synthesized compounds were characterized by FT-IR spectroscopy and ¹H and ¹³C NMR spectroscopy. The compounds were screened for their antibacterial activity by turbidimetric method using gram-negative bacteria (E. coli ATCC 8739) using turbidimetric method. The newly synthesized bis-thiourea derivatives bearing aryl side chains showed good antibacterial activity against E. coli. The effect of the molecular structure of the synthesized compounds on the antibacterial activity is discussed.     

Atomic Force Microscopic Investigations of Fibrils Formed by Complexation of Monochelic Polystyrenic Porphyrin and PEGylated Fullerene (C60)

Atomic force microscopic studies have been conducted for insight into the morphological aspects of monochelic porphyrin and fullerene complexes forming fibrils of continuous nature. Alternating dark and bright segments could be envisioned clearly, as individual porphyrin-fullerene repeating units. These fibrils also caused a remarkable red shift in the soret band absorption of porphyrin. Dynamic light scattering analysis was also conducted under different solvent conditions, which showed the swelling of fibrils when the solvent was changed from THF to water.     

Absorption spectrum of naphthalene in rare-gas matrices

The absorption spectrum of naphthalene has been studied in rare-gas matrices (RGM). Molar extinction coefficients have been determined and oscillator strengths of various $\text{π}{}^1\text{-π}$ transitions deduced. Bands in the 6.5 to 7.1 eV region, some of which were previously observed and interpreted as members of an impurity exciton (Rydberg) series, have been assigned to a $\text{π}{}^1\text{-π}$ transition. The results are compared with the theoretical prediction.     

Stability indicating liquid chromatographic method for simultaneous quantification of betamethasone valerate and tazarotene in in vitro and ex vivo studies of complex nanoformulation

Low‐potency corticosteroid betamethasone valerate and vitamin‐A tazarotene are used in combination for effective treatment of psoriasis. There is no robust high‐performance liquid chromatography analytical technique available for simultaneous estimation of betamethasone valerate and tazarotene in conventional and nanocarriers based formulations. A simple, accurate, robust isocratic high‐performance liquid chromatography method was developed for simultaneous estimation of betamethasone valerate and tazarotene in topical pharmaceutical formulations. The developed method was validated as per the regulatory guidelines. The validated method was linear over the concentration range of 150–6000 ng/mL (r² > 0.999) at 239 nm wavelength. Limits of detection and quantification of two analytes were 50 and 150 ng/mL, respectively. The %relative standard deviation for intraday and interday precision was less than 2%. The method was also evaluated in the presence of forced degradation conditions. The developed method was successfully applied for in vitro and ex vivo drug release studies of in‐house designed nanoformulations.     

Antioxidant potential of indigenous cyanobacterial strains in relation with their phenolic and flavonoid contents

Antioxidant activities of eight indigenous cyanobacterial strains belonging to the genera Oscillatoria, Chroococcidiopsis, Leptolyngbya, Calothrix, Nostoc and Phormidium were studied in relation with their phenolic and flavonoid contents, ranging 3.9–12.6 mg GAE g^?1 and 1.7–3.44 mg RE g^?1. The highest activities were shown by Leptolyngbya sp. SI-SM (EC₅₀ = 63.45 and 67.49 μg mL^?1) and Calothrix sp. SI-SV (EC₅₀ = 65.79 and 69.38 μg mL^?1) calculated with ABTS and DPPH assays. Significant negative correlations were seen between total phenolic and flavonoid contents and the antioxidant activities in terms of EC₅₀ values. Furthermore, HPLC detected 15 phenolic compounds with total concentrations ranging from 277.3 to 829.7 μg g^?1. The prevalent compounds in most of the strains were rutin, tannic acid, orcinol, phloroglucinol and protocatechuic acid. Cyanobacterial strains showed high potential as a good source of phenolic compounds with potent antioxidative potential which could be beneficial for food, cosmetic and pharmaceutical industries.     

Ionic liquid coated iron nanoparticles are promising peroxidase mimics for optical determination of H<Subscript>2</Subscript>O<Subscript>2</Subscript>

Ionic liquid coated nanoparticles (IL-NPs) consisting of zero-valent iron are shown to display intrinsic peroxidase-like activity with enhanced potential to catalyze the oxidation of the chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide. This results in the formation of a blue green colored product that can be detected with bare eyes and quantified by photometry at 652 nm. The IL-NPs were further doped with bismuth to enhance its catalytic properties. The Bi-doped IL-NPs were characterized by FTIR, X-ray diffraction and scanning electron microscopy. A colorimetric assay was worked out for hydrogen peroxide that is simple, sensitive and selective. Response is linear in the 30–300 μM H₂O₂ concentration range, and the detection limit is 0.15 μM.

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Graphical abstract Schematic of ionic liquid coated iron nanoparticles that display intrinsic peroxidase-like activity. They are capable of oxidizing the chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide. This catalytic oxidation generated blue-green color can be measured by colorimetry. Response is linear in the range of 30–300 μM H₂O₂ concentration, and the detection limit is 0.15 μM.

     

Nature of the copper-nitrosyl intermediates of copper nitrite reductases during catalysis

The design and synthesis of copper complexes that can reduce nitrite to NO has attracted considerable interest. They have been guided by the structural information on the catalytic Cu centre of the widespread enzymes Cu nitrite reductases but the chemically novel side-on binding of NO observed in all crystallographic studies of these enzymes has been questioned in terms of its functional relevance. We show conversion of NO₂⁻ to NO in the crystal maintained at 170 K and present ‘molecular movies’ defining events during enzyme turnover including the formation of side-on Cu-NO intermediate. DFT modelling suggests that both true {CuNO}¹¹ and formal {CuNO}¹⁰ states may occur as side-on forms in an enzymatic active site with the stability of the {CuNO}¹⁰ side-on form governed by the protonation state of the histidine ligands. Formation of a copper-nitrosyl intermediate thus needs to be accommodated in future design templates for functional synthetic Cu-NiR complexes.

Observation of side-on copper-nitrosyl intermediate and its confirmation by DFT during catalysis of copper nitrite reductases.     

Effects of temperature and solvent concentration on the solvent crystallization of palm-based dihydroxystearic acid with isopropyl alcohol

Palm-based dihydroxystearic acid of 69.55% purity was produced in a 500-kg-per-batch operation pilot plant and purified through solvent crystallization in a custom fabricated simultaneous batch crystallizer unit. The effects of temperature and solvent concentration on yield, particle size distribution and purity were studied. The purity was higher, while the yield and particle size were lower and smaller, respectively, at higher temperature and solvent concentration. The solvent crystallization process efficiency was rated at 66–69% when carried out with 70–80% isopropyl alcohol at 20 °C.