Determination of the anthraquinones aloe-emodin and aloin-A by liquid chromatography with mass spectrometric and diode array detection

Methods using liquid chromatography/mass spectrometry (LC/MS) and LC with diode array detection (DAD) in the UV range (LC/UV) were developed for the determination of low levels of the anthraquinones aloe-emodin and aloin-A (barbaloin) in aloe-based products. The methods were used to analyze several commercial products (liquids, semisolids, and solids) for the 2 anthraquinones. The wavelengths used for quantification of aloin-A, aloe-emodin, and emodin (internal standard) by DAD were 357, 257, and 289 nm, respectively. The on-column sensitivities were 0.25 and 0.05 ng by LC/UV and 0.01 and 0.025 ng by LC/MS for aloin-A and aloe-emodin, respectively. The methods are simple and sensitive and provide reproducible results; therefore, they are suitable for the determination of these anthraquinones in various aloe-based products.     

Cannabinoids,Phenolics, Terpenes and Alkaloids of Cannabis

Cannabis sativa is one of the oldest medicinal plants in the world. It was introduced into western medicine during the early 19th century. It contains a complex mixture of secondary metabolites, including cannabinoids and non-cannabinoid-type constituents. More than 500 compounds have been reported from C. sativa, of which 125 cannabinoids have been isolated and/or identified as cannabinoids. Cannabinoids are C₂₁ terpeno-phenolic compounds specific to Cannabis. The non-cannabinoid constituents include: non-cannabinoid phenols, flavonoids, terpenes, alkaloids and others. This review discusses the chemistry of the cannabinoids and major non-cannabinoid constituents (terpenes, non-cannabinoid phenolics, and alkaloids) with special emphasis on their chemical structures, methods of isolation, and identification.     

Phenothiazine-based chalcones as potential dual-target inhibitors toward cholinesterases (AChE,BuChE) and monoamine oxidases (MAO-A,MAO-B)

Chalcones targeting neurodegenerative diseases have been known as attractive structures in drug design and discovery. In this study, phenothiazine-based chalcones as ChEs and MAOs inhibitors were designed and synthesized via base-catalyzed Claisen-Schmidt condensation, and chemical structures of the compounds were elucidated by NMRs and HRMS. Compounds 3 and 9 showed promising inhibition potency against AChE enzyme with IC₅₀ values of 0.221 μM and 0.053 μM while compound 9 displayed remarkable inhibition potency toward MAO-B enzyme with IC₅₀ value of 0.048 μM. Compound 9 , as a dual-target inhibitor, selectively inhibited AChE and MAO-B enzymes. This promising behavior is an advantage for the compound since MAO-B and AChE inhibition have a role in Alzheimer's disease. Fused tricyclic ring systems such as phenothiazine incorporated with chalcone moiety being multitargeting ligands may help scientists for the rational design of novel lead compounds targeting neurodegenerative illnesses.     

New ferrocenyl guanidines as potent antioxidants,protein kinase inhibitors and cytotoxic agents against human leukemia THP-1 cell line

Russian Journal of General Chemistry - Six new ferrocenyl guanidines were synthesized and characterized by elemental analysis, FT-IR and 1H and 13C NMR. Compounds 1–6 were screened for...     

Spin gap and Luttinger liquid description of the NMR relaxation in carbon nanotubes

Recent NMR experiments by Singer et al. [Singer, Phys. Rev. Lett. 95, 236403 (2005).] showed a deviation from Fermi-liquid behavior in carbon nanotubes with an energy gap evident at low temperatures. Here, a comprehensive theory for the magnetic field and temperature dependent NMR 13C spin-lattice relaxation is given in the framework of the Tomonaga-Luttinger liquid. The low temperature properties are governed by a gapped relaxation due to a spin gap ( approximately 30 K), which crosses over smoothly to the Luttinger liquid behavior with increasing temperature.     

Exact many-electron ground states on the diamond Hubbard chain

Exact ground states of interacting electrons on the diamond Hubbard chain in a magnetic field are constructed which exhibit a wide range of properties such as flat-band ferromagnetism and correlation-induced metallic, half-metallic, or insulating behavior. The properties of these ground states can be tuned by changing the magnetic flux, local potentials, or electron density.     

Rhodium‐Catalyzed (5+1) Annulations Between 2‐Alkenylphenols and Allenes: A Practical Entry to 2,2‐Disubstituted 2H‐Chromenes

Readily available alkenylphenols react with allenes under rhodium catalysis to provide valuable 2,2‐disubstituted 2H‐chromenes. The whole process, which involves the cleavage of one C? H bond of the alkenyl moiety and the participation of the allene as a one‐carbon cycloaddition partner, can be considered a simple, versatile, and atom‐economical (5+1) heteroannulation. The reaction tolerates a broad range of substituents both in the alkenylphenol and in the allene, and most probably proceeds through a mechanism involving a rhodium‐catalyzed C? C coupling followed by two sequential pericyclic processes.     

The exact Schrieffer–Wolff transformation

The effective s–d spin interaction is derived exactly for the single-impurity Anderson model via a unitary transformation. This unitary transformation was calculated up to infinite order and no restrictions were imposed upon the coefficients of the Hubbard interaction and the hybridization. We also discuss briefly the impact of the obtained result on the magnetic properties of several Kondo compounds. This will shed new light on the understanding of the competition between the Kondo effect and the Ruderman–Kittel–Kasuya–Yosida interaction and reinterpret the Doniach diagram.     

The elementary stages of electroreduction of alkyl(hetero)arylsulfones in water-organic media

Intermediates (IM) of methyl(2-pyridyl)sulfone (MPS) and tert-butyl(2-pyridyl)sulfone (TBPS) formed upon the transfer of the first electron are studied by methods of laser photoelectron emission (LPE). The capture constants of solvated electrons by the MPS and TBPS molecules were determined. The time-resolved voltammograms of each sulfone measured in water-organic mixtures (20–80% ethanol or 60% DMSO) are found to demonstrate a redox wave with half-wave potentials E _1/2 = −1.34 and −1.37 V for MPS and TBPS, respectively. The dependence of rate constants for the one-electron IM reduction and oxidation on the potential is shown to obey the slow-discharge equation and the absolute magnitudes of rate constants are determined. The characteristic times of homogeneous transformations (decomposition, protonation) of MPS and TBPS radical anions do not exceed 3 × 10⁻⁷ s. The LPE data are compared with the results of preparative electrolysis and the mechanisms of both electrochemical and homogeneous reactions of IM are discussed.     

Synthesis and antifungal evaluation of 1-aryl-2-dimethyl- aminomethyl-2-propen-1-one hydrochlorides

The development of resistance to current antifungal therapeutics drives the search for new effective agents. The fact that several acetophenone-derived Mannich bases had shown remarkable antifungal activities in our previous studies led us to design and synthesize some acetophenone-derived Mannich bases, 1-8 and 2-acetylthiophene-derived Mannich base 9, 1-aryl-2-dimethylaminomethyl-2-propen-1-one hydrochloride, to evaluate their antifungal activities. The designed chemical structures have α,β-unsaturated ketone moieties, which are responsible for the bioactivities of the Mannich bases. The aryl part was C?H?(1); 4-CH?C?H? (2); 4-CH?OC?H? (3); 4-ClC?H? (4); 4-FC?H? (5); 4-BrC?H? (6); 4-HOC?H? (7); 4-NO?C?H? (8); and C?H?S(2-yl) (9). In this study the designed compounds were synthesized by the conventional heating method and also by the microwave irradiation method to compare these methods in terms of reaction times and yields to find an optimum synthetic method, which can be applied for the synthesis of Mannich bases in further studies. Since there are limited number of studies reporting the synthesis of Mannich bases by microwave irradiation, this study may also contribute to the general literature on Mannich bases. Compound 7 was reported for the first time. Antifungal activities of all compounds and synthesis of the compounds by microwave irradiation were also reported for the first time by this study. Fungi (15 species) were used for antifungal activity test. Amphotericin B was tested as an antifungal reference compound. In conclusion, compounds 1-6, and 9, which had more potent (2-16 times) antifungal activity than the reference compound amphotericin B against some fungi, can be model compounds for further studies to develop new antifungal agents. In addition, microwave irradiation can be considered to reduce reaction period, while the conventional method can still be considered to obtain compounds with higher reaction yields in the synthesis of new Mannich bases.