scholarly journals Oxidative Oligomerization of DBL Catechol, a potential Cytotoxic Compound for Melanocytes, Reveals the Occurrence of Novel Ionic Diels-Alder Type Additions

2020 ◽  
Vol 21 (18) ◽  
pp. 6774
Author(s):  
Manickam Sugumaran ◽  
Kubra Umit ◽  
Jason Evans ◽  
Rachel Muriph ◽  
Shosuke Ito ◽  
...  
Keyword(s):  
Spectroscopic Studies ◽  
Diels Alder ◽  
Oxidation Products ◽  
Side Chain ◽  
Liquid Chromatography Mass Spectrometry ◽  
Carbonyl Derivative ◽  
Cytotoxic Compound ◽  
Whitening Agent ◽  
Uv Visible ◽  
Oxidation Chemistry

The exposure of human skin to 4-(4-hydroxyphenyl)-2-butanone (raspberry ketone, RK) is known to cause chemical/occupational leukoderma. RK is a carbonyl derivative of 4-(4-hydroxyphenyl)-2-butanol (rhododendrol), a skin whitening agent that was found to cause leukoderma in skin of many consumers. These two phenolic compounds are oxidized by tyrosinase and the resultant products seem to cause cytotoxicity to melanocytes by producing reactive oxygen species and depleting cellular thiols through o-quinone oxidation products. Therefore, it is important to understand the biochemical mechanism of the oxidative transformation of these compounds. Earlier studies indicate that RK is initially oxidized to RK quinone by tyrosinase and subsequently converted to a side chain desaturated catechol called 3,4-dihydroxybenzalacetone (DBL catechol). In the present study, we report the oxidation chemistry of DBL catechol. Using UV–visible spectroscopic studies and liquid chromatography mass spectrometry, we have examined the reaction of DBL catechol with tyrosinase and sodium periodate. Our results indicate that DBL quinone formed in the reaction is extremely reactive and undergoes facile dimerization and trimerization reactions to produce multiple isomeric products by novel ionic Diels-Alder type condensation reactions. The production of a wide variety of complex quinonoid products from such reactions would be potentially more toxic to cells by causing not only oxidative stress, but also melanotoxicity through exhibiting reactions with cellular macromolecules and thiols.

scholarly journals New Brightener for Zn-Fe Alloy Plating from Sulphate Bath

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
B. M. Praveen ◽  
T. V. Venkatesha
Keyword(s):  
Grain Size ◽  
Metal Ion ◽  
Condensation Product ◽  
Spectroscopic Studies ◽  
Sem Images ◽  
Alloy Electrodeposition ◽  
Fine Grained ◽  
Polarization Studies ◽  
Uv Visible ◽  
Sulphate Bath

Zn-Fe alloy electrodeposition was carried out in the presence of condensation product 2-{[(1E)-(3,4-dimethoxyphenyl)methylidene]amino}-3-hydroxypropanoic acid formed between veratraldehyde and serine in acid sulphate bath. Hull cell was used for optimizing the operating parameters and bath constituents. During deposition, the potential was shifted towards cathodic direction in the presence of addition agents and brightener. The polarization studies show that deposition taking place in basic bath and optimum bath was 1.08 and 1.15 V, respectively. Current efficiency and throwing power were reached around 85% and 26%, respectively. The SEM images of bright deposit indicated its fine-grained nature and appreciable reduction in the grain size. XRD studies have showed that the grain size of the deposit generated from optimum bath was 16 nm. UV-visible spectroscopic studies confirm the formation of complex between metal ion and brightener.

Structural Study of an Unusual Diels-Alder Adduct

1992 ◽  
Vol 45 (12) ◽  
pp. 2089 ◽  
Author(s):  
EL Ghisalberti ◽  
BW Skelton ◽  
AH White
Keyword(s):  
Single Crystal ◽  
Diffraction Study ◽  
Structural Study ◽  
Spectroscopic Studies ◽  
Diels Alder ◽  
X Ray Diffraction ◽  
X Ray ◽  
Naturally Occurring ◽  
Chemical Evidence ◽  
Alder Adduct

The structure of the compound obtained on heating the naturally occurring clerodane furanoditerpene (1) had been formulated as (2) on the basis of spectroscopic studies. A single-crystal X-ray diffraction study on the dihydro derivative of (2) has confirmed this and provides support for the stereochemistry previously assigned to (1) on the basis of chemical evidence.

Synthesis of perialkynylated tetrapyrazinoporphyrazines and its Optical Properties

2009 ◽  
Vol 2009 (5) ◽  
pp. 312-316 ◽  
Author(s):  
Chun Keun Jang ◽  
Jae Yun Jaung
Keyword(s):  
Optical Properties ◽  
Nmr Spectroscopy ◽  
Laser Desorption ◽  
Diels Alder ◽  
Visible Spectroscopy ◽  
H Nmr ◽  
Uv Visible ◽  
Tof Ms ◽  
Matrix Assisted Laser ◽  
Matrix Assisted Laser Desorption

Some phthalocyanines soluble in organic solvents have been developed by peripheral introduction of substituent groups. We report a new method for preparation of the polyphenyl-substituted dicyanopyrazines based on the [2 + 4] Diels-Alder cycloaddition of the tetraphenylcyclopentadienone to an ethynyl compound. The synthesised tetrapyrazinoporphyrazinato metal complexes were characterised by UV-visible spectroscopy, MALDI-TOF-Ms (matrix-assisted laser desorption ionisation time-of-flight mass) spectroscopy, and 1H NMR spectroscopy.

A Newly Designed Cryostat for Absorption Spectroscopic Studies of Liquids, Solids, and the Interphases

1988 ◽  
Vol 42 (8) ◽  
pp. 1401-1404 ◽  
Author(s):  
J. C. Cornut ◽  
P. V. Huong ◽  
A. Graja ◽  
G. Daleau
Keyword(s):  
Solid State ◽  
Absorption Spectroscopy ◽  
Thermal Convection ◽  
Spectroscopic Studies ◽  
Sample Cell ◽  
Cold Stream ◽  
Uv Visible ◽  
Freezing Chamber

A double jacket cryostat based on thermal convection between a gaseous cold stream filled in a freezing chamber and the sample cell is described. This device is designed for absorption spectroscopy in the infrared and in the UV-visible regions for gases, liquids, liquefied gases, and solids, as well as for the transitions between these phases or between phases in the solid state, over the range 85 to 340 K, at variable thicknesses and under a pressure of up to 10 bars.

Synthesis and Studies on the Effect of Phenyl Side – Chain Content on Refractive Index of Polysiloxane Resin

2015 ◽  
Vol 754-755 ◽  
pp. 881-885
Author(s):  
Rafiza Ramli ◽  
Ng Chee Mang ◽  
Zulkifli Ahmad ◽  
Mariatti Jaafar ◽  
Mohd Remy Rozainy Mohd Arif Zainol
Keyword(s):  
Refractive Index ◽  
High Refractive Index ◽  
Linear Increase ◽  
Solution Viscosity ◽  
Side Chain ◽  
High Brightness ◽  
Structural Modifications ◽  
H Nmr ◽  
Siloxane Oligomers ◽  
Uv Visible

A series of high refractive index of α,ω-vinyl silyl terminated polydimethylsiloxane-co-polydiphenylsiloxane was synthesized by the equilibration ring opening – anionic polymerization of cyclic organo-siloxane oligomers in the present of 1,3-divinyltetramethyldisiloxane as terminating agent. Structural modifications were characterized by use of FTIR, H-NMR, and solution viscosity. UV-visible spectroscopy was analyzed which reveal a good transmittance in the region 400 – 750 nm radiation for all polysiloxanes.The presence of diphenylsiloxane unit results in a linear increase of the refractive index of the resin. These features favor good application as encapsulant for high brightness LED (HBLED) packaging.

scholarly journals Spectroscopic studies on the potassium 1-fluorobenzoyltrifluoroborate salt by using the FT-IR, Raman and UV–Visible spectra and DFT calculations

2020 ◽  
Vol 1204 ◽  
pp. 127534 ◽  
Author(s):  
Maximiliano A. Iramain ◽  
Ana E. Ledesma ◽  
Elizabeth Imbarack ◽  
Patricio Leyton Bongiorno ◽  
Silvia Antonia Brandán
Keyword(s):  
Dft Calculations ◽  
Spectroscopic Studies ◽  
Visible Spectra ◽  
Ft Ir ◽  
Uv Visible

Synthesis and optical properties of tetrapyrazinoporphyrazine containing phenylene dendron unit as a peripheral substituent

2009 ◽  
Vol 13 (08n09) ◽  
pp. 939-948 ◽  
Author(s):  
Chun Keun Jang ◽  
Jae Yun Jaung
Keyword(s):  
Catalytic Properties ◽  
Diels Alder ◽  
Laser Desorption Ionization ◽  
Visible Spectroscopy ◽  
Ionization Time ◽  
H Nmr ◽  
Flight Mass Spectrometry ◽  
Out Of Plane ◽  
New Type ◽  
Uv Visible

A dendritic shell can create a distinct micro-environment within its core. It also has the advantage of possessing unique photochemical, photophysical, electrochemical, and catalytic properties. Polyphenylene dendrons, which are characterized by their shape-persistent structures and out-of-plane twisted phenyl components, have previously been successfully attached to various functional groups. We have recently developed a convenient method for synthesizing a new type of porphyrazine that contains both flexible (linear) and more rigid (dendritic) groups. The synthesis of this completely aromatic and dendronic structure is unique in that it is based on a [2+4] Diels-Alder cycloaddition of tetraphenylcyclopentadienone to an ethynyl compound, followed by the elimination of carbon monoxide. In this study, tetrapyrazinoporphyrazinato metal and metal-free complexes were prepared by mixing 2,3-dicyano-5-polyphenylpyrazines with magnesium in n-butanol. The synthesized tetrapyrazinoporphyrazines were characterized by UV-visible spectroscopy, MALDI-TOF-MS (matrix-assisted laser desorption/ionization time-of-flight mass) spectrometry, elemental analysis and 1 H NMR spectroscopy.

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