Analysis of acetylcholinesterase inhibitors by extraction in choline saccharinate aqueous biphasic systems.

Ionic liquid-based aqueous biphasic systems (IL-ABS) formed by ILs composed of ions of low toxicity, choline ([Chol]+) coupled with saccharinate ([Sac]-) and acesulfamate ([Ace]-), and inorganic salts with distinct water-structuring properties were employed for simultaneous extraction and concentration of acetylcholinesterase (AChE) inhibitors - galantamine (gal), N-desmethyl galantamine (des) and ungiminorine (ung). Comprehensive experiments aimed to assess the influence of salt and IL type and concentration, as well as the pH and temperature on the phase-forming ability and distribution of the target alkaloids between the two phases formed reveled that the IL anion and pH are the most important factors. At the optimal conditions found a quantitative recovery into the IL-rich phase of gal, des and ung was achieved in a single extractive step. These results were further used as a platform for the development of a simple and safer sample pretreatment method for analysis of the three analytes, followed by RP-HPLC/UV detection. The method showed satisfactory analytical performance, the latter allowing quantitative determination of these AChE inhibitors in pharmaceutical dosage form and in human urine.

Synthesis and antioxidant activity of polyhydroxylated trans-restricted 2-arylcinnamic acids.

A series of sixteen polyhydroxylated trans-restricted 2-arylcinnamic acid analogues 3a-p were synthesized through a one-pot reaction between homophthalic anhydrides and various aromatic aldehydes, followed by treatment with BBr3. The structure of the newly synthesized compounds was confirmed by spectroscopic methods and the configuration around the double bond was unequivocally estimated by means of gated decoupling 13C-NMR spectra. It was shown that the trans-cinnamic acid fragment incorporated into the target compounds' structure ensures the cis-configuration of the stilbene backbone and prevents further isomerization along the carbon-carbon double bond. The antioxidant activity of compounds 3a-p was measured against 1,1-diphenyl-2-picrylhydrazyl (DPPH●), hydroxyl (OH●) and superoxide (O2●▬) radicals. The results obtained showed that the tested compounds possess higher activities than natural antioxidants such as protocatechuic acid, caffeic acid and gallic acid. Moreover, it was shown that a combination of two different and independently acting fragments of well-known pharmacological profiles into one covalently bonded hybrid molecule evoke a synergistic effect resulting in higher than expected activity. To rationalize the apparent antioxidant activity and to establish the mechanism of action, a SAR analysis and DFT quantum chemical computations were also performed.

One-pot synthesis and radical scavenging activity of novel polyhydroxylated 3-arylcoumarins.

An unexpected domino rearrangement brought about the development of a novel one-pot procedure for synthesis of coumarins. This protocol allowed the gram-scale synthesis of a variety of polyhydroxylated derivatives 3a-p, from readily available starting materials at a low cost. Based on two proven intermediates, a probable mechanism consisting of boron tribromide induced demethylation/lactone ring opening/elimination/isomerization/lactone ring closure reaction sequence of in situ formed 3-aryl-3,4-dihydroisocoumarin-4-carboxylic acids was deduced. Compared to the common methods, used for the synthesis of coumarins, the proposed herein possesses great advantages, such as mild conditions, good yields for short reaction time, simple work-up procedure and easy isolation of the final products. The structure of the newly synthesized compounds 3a-p was established by spectroscopic methods ((1)H NMR, (13)C NMR, IR, MS and HRMS) and their radical scavenging activity was evaluated in vitro against 1,1-diphenyl-2-picrylhydrazyl free radical (DPPH). The results obtained show that compounds 3g-p posses higher radical scavenging activity (3.16 ≤ SC50 [µM] ≤ 6.82) than well-known antioxidants such as trolox, protocatechuic acid, caffeic acid and gallic acid (SC50 [µM] = 9.34, 8.83, 9.48, 5.33, respectively), which is a precondition for promising antioxidant activity of these compounds to be expected.

A novel one-pot synthesis and preliminary biological activity evaluation of cis-restricted polyhydroxy stilbenes incorporating protocatechuic acid and cinnamic acid fragments.

A series of new stilbenes 4a-e, 5 were synthesized through a novel one-pot Perkin-like reaction between 6,7-dimethoxyhomophthalic anhydride and aromatic aldehydes, followed by treatment with BBr3. This synthesis is straightforward and allows polyhydroxylated cis-stilbenes gathering two well-known pharmacophoric fragments to be obtained in good yields and for short reaction times. The structure of the newly synthesized compounds was established by spectroscopic methods ((1)H NMR, (13)C NMR, IR and HRMS) and the double bond configuration was unequivocally elucidated by means of gated decoupling (13)C NMR spectra and 2D NOESY experiments. Preliminary differentiating screening of their radical scavenging, antibacterial, anti-fungal and tyrosinase inhibitory activity was further performed. The results obtained suggest that the tested compounds possess a triple biological action as potent radical scavengers, antifungal agents and tyrosinase inhibitors in micromolar concentration. The most promising bioactive compound amongst the others was 4a, acting as excellent radical scavenger against DPPH(•) radical (IC50 ≤ 10 µM), antifungal agent suppressing the growth of Fusarium graminearum (89% inhibition at 0.17 µmol/mL), and tyrosinase inhibitor showing higher activity than hydroquinone at 23 µM.

(S)-Methyl 2-[(3R,4R)-2-benzyl-3-(2-fur-yl)-1-oxo-1,2,3,4-tetra-hydro-isoquinoline-4-carboxamido]-3-(1H-indol-3-yl)propanoate.

The title compound, C(33)H(29)N(3)O(5), was synthesized by the reaction of racemic trans-2-benzyl-3-(2-fur-yl)-1-oxo-1,2,3,4-tetra-hydro-isoquinoline-4-carboxylic acid, l-tryptophan methyl ester and diisopropylcarbodiimide in dry dichloro-methane. The furan ring is disordered over two positions in a 0.859 (14):0.141 (14) ratio. In the 1,2,3,4-tetra-hydro-iso-quin-oline ring system, the heterocyclic ring is not planar, with puckering parameters Q(T) = 0.448 (2) Å, θ = 64.9 (3) and ϕ = 268.3 (3)°. The crystal is extended into a three-dimensional supra-molecular architecture through inter-molecular N-H⋯O hydrogen bonds and C-H⋯π inter-actions. The absolute structure was assigned by reference to the chiral starting material.

Methyl trans-(±)-1-oxo-2-phenethyl-3-(thio-phen-2-yl)-1,2,3,4-tetra-hydro-isoquinoline-4-carboxyl-ate.

In the title compound, C(23)H(21)NO(3)S, the piperidine ring of the tetra-hydro-isoquinolinone unit adopts a screw-boat conformation. The thio-phene ring is disordered in a 0.700 (3):0.300 (3) ratio by an approximate 180° rotation of the ring around the C-C bond linking the ring to the tetra-hydro-isoquinolinone unit. The benzene ring of the tetra-hydro-isoquinolinone unit makes dihedral angles of 83.1 (2) and 62.38 (11)° with the major occupancy thio-phene ring and the phenyl ring, respectively. The dihedral angle between the phenyl ring and the thio-phene ring is 71.0 (2)°. In the crystal structure, mol-ecules are linked together by inter-molecular C-H⋯O and C-H⋯π inter-actions.

(±)-trans-6,7-Dimeth-oxy-1-oxo-3-(2-thien-yl)isochroman-4-carboxylic acid.

The title compound, C(16)H(14)O(6)S, was synthesized by the reaction of 6,7-dimethoxy-homophthalic anhydride with thio-phene-2-carbaldehyde in the presence of 4-(dimethyl-amino)pyridine (DMAP) as a basic catalyst. The thio-phene ring of the title mol-ecule is disordered over two sites with occupancies of 0.877 (3) and 0.123 (3). The disorder corresponds to an approximate 180° rotation of the thio-phene ring with respect to the C-C bond linking it to the rest of the mol-ecule. The six-membered ring of the 3,4-dihydro-isochromanone ring system is not planar [puckering parameters Q(T) = 0.571 (2) Å, θ = 115.2 (2)° and ϕ = 99.1 (2)°]. The benzene ring of the 3,4-dihydro-isochromanone ring system makes dihedral angles of 75.0 (2) and 77.2 (5)° with the disordered thio-phene rings. Inter-molecular O-H⋯O and C-H⋯O hydrogen bonds, as well as C-H⋯π inter-actions, lead to the observed supra-molecular structure.

Methyl trans-rac-2-hexyl-1-oxo-3-(2-pyrid-yl)-1,2,3,4-tetra-hydroisoquinoline-4-carboxyl-ate.

The title compound, C(22)H(26)N(2)O(3), was synthesized by esterification of trans-rac-2-hexyl-1-oxo-3-(2-pyrid-yl)-1,2,3,4-tetra-hydro-isoquinoline-4-carboxylic acid in the presence of H(2)SO(4) in methanol. The dihedral angle between the benzene and pyridine rings is 84.46 (17)°. The piperidine ring adopts a screw-boat conformation. In the crystal, inversion dimers linked by two C-H⋯O bonds occur.

trans-rac-[1-Oxo-2-phenethyl-3-(2-thien-yl)-1,2,3,4-tetra-hydro-isoquinolin-4-yl]methyl 4-methyl-benzene-sulfonate.

The title compound, C(29)H(27)NO(4)S(2), was synthesized by reaction of trans-rac-4-(hydroxy-meth-yl)-2-phenethyl-3-(thio-phen-2-yl)-3,4-dihydro-isoquinolin-1(2H)-one and 4-methyl-benzene-1-sulfonyl chloride in the presence of Et(3)N in CH(2)Cl(2). The relative orientations of the benzene ring (A) of the 3,4-dihydro-isoquinolinone ring system, the thio-phene ring (B), the benzene ring (C) of the methyl-benzene group and the phenyl ring (D) result in the following dihedral angles: A/B = 80.91 (16), A/C = 22.79 (18), A/D = 9.9 (2), B/C = 80.73 (19), B/D = 88.9 (2) and C/D = 29.9 (2)°. The crystal structure is stabilized by weak inter-molecular C-H⋯O hydrogen bonds and C-H⋯π inter-actions.

Preliminary evaluation of antimicrobial activity of diastereomeric cis/trans-3-aryl(heteroaryl)-3,4-dihydroisocoumarin-4-carboxylic acids.

Preliminary differentiating screening of the antibacterial and antifungal activity of a series of diastereomeric cis/trans-3-aryl(heteroaryl)-3,4-dihydroisocoumarin-4-carboxylic acids (3a-i) was performed by the agar diffusion method against twelve microorganism strains of different taxonomic groups. S. aureus and A. niger were the most sensitive strains to the antibiotic effect of the tested compounds, both inhibited by 10 of 12 compounds. The most potent antibacterial agent was cis-3-phenyl-3,4-dihydroisocoumarin-4-carboxylic acid (cis-3a), exhibiting activity against all seven bacterial test strains.