Synthesis of (4R)-thiazolidine carboxylic acid and evaluation of antioxidant potential.

We report here the synthesis as well as antioxidant activity of a series of 2-aryl thiazolidine-4-carboxylic acids, including two novel derivatives. They were synthesized by nucleophilic cyclic condensation of L-cysteine hydrochloride with a range of aromatic aldehydes. Their in vitro antioxidant activity was evaluated by DPPH radical scavenging assay. It was observed that the aromatic substituent at C-2 of thiazolidine ring effects the antioxidant potential of the thiazolidine derivatives. The nature and position of the substituents on aromatic ring were correlated with antioxidant activity. Compounds with -OCH3 group on aromatic ring showed a better radical scavenging property than the other groups such as -Cl, -F, and -NO2. The presence of phenyl ring thus enhanced radical scavenging activity.

Combination Therapy of Clinically Approved Antifungal Drugs Is Enhanced by Conjugation with Silver Nanoparticles

Silver nanoparticles (SN) have been recently developed as a new class of antimicrobial agents against numerous pathogenic microorganisms. SN have also been used as efficient drug delivery systems and have been linked with increasing drug potency. Here, we demonstrated the enhanced antifungal efficacy of nystatin (NYT) and fluconazole (FLU) after conjugation with SN. The antifungal bioactivity of NYT- and FLU-coated SN was evaluated against Candida albicans ATCC 10231 and Aspergillus brasiliensis ATCC 16404 by the agar tube dilution method. The aim of this study was to determine and compare the antifungal efficacy of NYT and FLU with their SN and, finally, the combination of both nanoparticles as NYT-SN + FLU-SN against pathogenic fungi. The results indicated that all test samples showed a dose-dependent response against tested fungi. SN significantly enhanced the antifungal effects of NYT and FLU as compared to drugs alone. We observed a remarkable increase in the percent inhibition of both fungi (90-100%) when treated with a combination of both nanoparticles NYT-SN + FLU-SN at 200 μg/mL only. Furthermore, the morphological modifications occurred at the surface of fungal species were also analyzed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). While tested against primary human cell line, all SN showed negligible cytotoxicity. Hence, these results suggest that the combination of SN with NYT and FLU may have clinical implications in the treatment of fungal infections. However, in vivo studies are needed before recommending the use of these nanoparticles safely in clinical situations

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Combination Therapy of Clinically Approved Antifungal Drugs Is Enhanced by Conjugation with Silver Nanoparticles.

Silver nanoparticles (SN) have been recently developed as a new class of antimicrobial agents against numerous pathogenic microorganisms. SN have also been used as efficient drug delivery systems and have been linked with increasing drug potency. Here, we demonstrated the enhanced antifungal efficacy of nystatin (NYT) and fluconazole (FLU) after conjugation with SN. The antifungal bioactivity of NYT- and FLU-coated SN was evaluated against Candida albicans ATCC 10231 and Aspergillus brasiliensis ATCC 16404 by the agar tube dilution method. The aim of this study was to determine and compare the antifungal efficacy of NYT and FLU with their SN and, finally, the combination of both nanoparticles as NYT-SN + FLU-SN against pathogenic fungi. The results indicated that all test samples showed a dose-dependent response against tested fungi. SN significantly enhanced the antifungal effects of NYT and FLU as compared to drugs alone. We observed a remarkable increase in the percent inhibition of both fungi (90-100%) when treated with a combination of both nanoparticles NYT-SN + FLU-SN at 200 µg/mL only. Furthermore, the morphological modifications occurred at the surface of fungal species were also analyzed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). While tested against primary human cell line, all SN showed negligible cytotoxicity. Hence, these results suggest that the combination of SN with NYT and FLU may have clinical implications in the treatment of fungal infections. However, in vivo studies are needed before recommending the use of these nanoparticles safely in clinical situations.

Novel fluorene-based supramolecular sensor for selective detection of amoxicillin in water and blood.

Synthesis, characterization and molecular recognition properties of fluorene based supramolecular cleft 1 is reported. The cleft molecule 1 was prepared in a single-step with good yield (85% yield), by linking Fluorene with 1-ethyl piperazine. The cleft molecule 1 was carefully characterized using various spectroscopic techniques such as NMR and mass spectrometry. The supramolecular interaction of cleft 1 with amoxicillin, 6APA, aspirin, captopril, cefotaxime, ceftriaxone, cefuroxime, diclofenac, penicillin, and cephradine was evaluated by fluorescent spectroscopy. The molecular recognition studies showed that amoxicillin selectively binds with cleft 1 in the presence of other drugs. The analytical method developed for the supramolecular interaction of molecular cleft 1 and amoxicillin was validated at varying pH, concentration and temperature during recognition process. Job's plots indicated that the stochiometry of the interactions between the cleft 1 and the amoxicillin was 1:1.

Phytochemicals from Dodonaea viscosa and their antioxidant and anticholinesterase activities with structure-activity relationships.

Context Dodonaea viscosa (L.) Jacq (Sapindaceae) has been used in traditional medicine as antimalarial, antidiabetic and antibacterial agent, but further investigations are needed. Objective This study determines the antioxidant and anticholinesterase activities of six compounds (1-6) and two crystals (1A and 3A) isolated from D. viscosa, and discusses their structure-activity relationships. Materials and methods Antioxidant activity was evaluated using six complementary tests, i.e., ß-carotene-linoleic acid; DPPH(•), ABTS(•+), superoxide scavenging, CUPRAC and metal chelating assays. Anticholinesterase activity was performed using the Elman method. Results Clerodane diterpenoids (1 and 2) and phenolics (3-6) - together with three crystals (1A, 3A and 7A) - were isolated from the aerial parts of D. viscosa. Compound 3A exhibited good antioxidant activity in DPPH (IC50: 27.44 ± 1.06 µM), superoxide (28.18 ± 1.35% inhibition at 100 µM) and CUPRAC (A0.5: 35.89 ± 0.09 µM) assays. Compound 5 (IC50: 11.02 ± 0.02 µM) indicated best activity in ABTS assay, and 6 (IC50: 14.30 ± 0.18 µM) in ß-carotene-linoleic acid assay. Compounds 1 and 3 were also obtained in the crystal (1A and 3A) form. Both crystals showed antioxidant activity. Furthermore, crystal 3A was more active than 3 in all activity tests. Phenol 6 possessed moderate anticholinesterase activity against acetylcholinesterase and butyrylcholinesterase enzymes (IC50 values: 158.14 ± 1.65 and 111.60 ± 1.28 µM, respectively). Discussion and conclusion This is the first report on antioxidant and anticholinesterase activities of compounds 1, 2, 5, 6, 1A and 3A, and characterisation of 7A using XRD. Furthermore, the structure-activity relationships are also discussed in detail for the first time.

Synthesis, characterization and Cu(2+) triggered selective fluorescence quenching of Bis-calix[4]arene tetra-triazole macrocycle.

A novel fluorescent bis-calix[4]arene macrocycle 9 incorporating metal-binding pockets was successfully prepared. The structure of macrocycle 9 and its precursors were characterized via EI-MS, MALDI-TOF-MS, ESI-MS, (1)H NMR, (13)CNMR, 2D NMR, and X-ray crystallography. The macrocycle 9 displayed selective fluorescence quenching after interacting with Cu(2+) in the presence competing metal cations including Mg(2+), Ca(2+), Ba(2+), Ag(+), Zn(2+), Ti(4+),Cd(2+), Hg(2+), Pb(2+), In(3+), La(3+), Cr(3+), Ni(2+), Sb(3+), V(5+), Fe(3+), Co(2+), Sn(2+), Sn(2+), and Tl(+). The Cu(2+) limit of detection was found to be 40 nM much lower than its threshold level (∼ 20 µM) in drinking water permitted by the U.S Environmental Protection Agency (EPA). Furthermore, drinking water samples from Karachi University (Pakistan) spiked with Cu(2+) were analysed with the sensing system and the results showed an excellent agreement with the fluorescence quenching phenomenon of macrocycle 9 examined in deionized water. Importantly, the chemosensor 9 could be used to detect Cu(2+) in living cells.

Govanoside A, a new steroidal saponin from rhizomes of Trillium govanianum.

A new spirostane steroidal saponin, govanoside A (1) along with three known compounds borassoside E (2) pennogenin (3) and diosgenin (4) were isolated from rhizomes of Trillium govanianum. Their structures were elucidated through 1D, 2D-NMR spectroscopic data analysis and acid hydrolysis. Compound (2) in genus Trillium and all compounds (1-4) in T. govanianum are reported herein for the first time. Furthermore, compounds 1 &2 exhibited good to moderate activities against Aspergillus niger ATCC 16888, Aspergillus flavus ATCC 9643, Candida albicans ATCC 18804, and Candida glabrata ATCC 90030. This is a significant finding keeping in view the limited antifungal drugs for aspergillosis and candidiasis.

GABA(A) receptor modulation and neuropharmacological activities of viscosine isolated from Dodonaea viscosa (Linn).

The objective of the present study was to evaluate the modulation of GABA-evoked currents by the flavonoid viscosine at recombinant GABA(A) receptors, and subsequently to study its anxiolytic, sedative and anticonvulsant activities. Viscosine (1-300µM) positively modulated GABA-evoked currents at human α1ß2γ2L and α2ß2γ2L GABA(A) receptors expressed in Xenopus oocytes in a flumazenil insensitive manner. In behavioral studies, viscosine at doses of 10-100mg/kg (i.p.) exerted significant anxiolytic effects in the elevated plus maze, light-dark and open field tests (*P<0.05, **P<0.01, ***P<0.001 n=6, One-way ANOVA post-Dunnett's test), and sedative effects at high doses (100mg/kg i.p.) in hole board and thiopental induced sleep time tests. The anxiolytic effect in the elevated plus maze test was not blocked by flumazenil whereas pentylenetetrazole (PTZ) completely attenuated the effect, indicating that the activity was mediated via the non-benzodiazepine sites of GABA(A) receptors. Furthermore, viscosine at doses of 10-100mg/kg (i.p.) exerted anticonvulsant effects in a dose-dependent manner in PTZ, picrotoxin and bicuculline induced seizure paradigms (*P<0.05, **P<0.01,***P<0.001 n=6, One-way ANOVA post-Dunnett's test). In conclusion, the results of the present study suggest that the anxiolytic and anticonvulsant actions of viscosine are likely mediated via its positive allosteric modulatory action of GABA at different GABA(A) receptor subtypes.

Green synthesis and molecular recognition ability of patuletin coated gold nanoparticles.

Patuletin isolated from Tagetespatula was used as a capping and reducing agent to synthesize in one pot gold nanoparticles capped with patuletin. Conjugation of gold with patuletin was confirmed by FT-IR and UV-visible spectroscopy and amount of patuletin conjugated to gold nanoparticles was found to be 63.2% by weight. Particle sizes were measured by atomic force microscopy (AFM) and were found to have a mean diameter of about 45 nm. Patuletin-coated gold nanoparticles were found to be highly fluorescent. To examine their potential as chemical sensors, they were contacted with fourteen different drugs. Of these drugs, only one, piroxicam, was found to quench luminescence. Quenching obeyed Beer's law in a concentration range of 20-260 µM. Important for molecular recognition applications, fluorescence quenching by piroxicam was not affected by pH variation, elevated temperatures, addition of other drugs and addition of blood plasma to the colloidal suspensions.

Urease inhibitory constituents from Daphne retusa.

The bioassay-guided fractionation of Daphne retusa Hemsl. has led to the isolation of a new aryl tetrahydronaphthalene lignan derivative named as daphnretusic acid (1), along with six new source compounds such as 5,7-dihydroxyflavone (2), 7-hydroxyflavone (3), 6-methoxyflavone (4), (+) pinoresinol (5), (+) sesamin (6), and ß-sitosterol-3-O-ß-D-glucopyranoside (7). Their structures were elucidated by (1)H NMR, (13)C NMR, 1D, 2D NMR, UV, IR, and EIMS analyses. All the fractions (n-hexane, CHCl3, AcOEt, CH3OH, and water) and pure compounds (1-7) were subjected to the assay of urease and α-chymotrypsin inhibitory activities. Chloroform and methanol soluble fractions showed moderate urease inhibition. Compound 2 exhibited significant urease inhibition with IC50 value 60.4 ± 0.72 µM, whereas compounds 1 and 3-7 remained inactive during urease inhibition and α-chymotrypsin bioassays.

New dimeric and trimeric coumarin glucosides from Daphne retusa Hemsl.

New dimeric and a trimeric coumarin glucosides namely Daphneretusin A (1) Daphneretusin B (2) along with three known oligomers (3-5) were obtained as a result of bioassay guided fractionation of Daphne retusa Hemsl. Fractions (n-hexane, CHCl3, AcOEt, CH3OH and water) exhibited potent radical scavenging activity in relevant non-physiological bioassays. The structures of isolated compounds were elucidated by UV, IR, EIMS, FAB-MS, 1D, and 2D NMR spectroscopic analysis.

Biotransformation of clerodane diterpenoids by Rhizopus stolonifer and antibacterial activity of resulting metabolites.

Microbial transformation of clerodane lactone (1) by a plant pathogen fungus, Rhizopus stolonifer, resulted in the production of metabolites 3 and 4. While incubation of clerodane methyl ester (2) by R. stolonifer yielded metabolites 5-8. The structures of the transformed products were determined by the spectroscopic techniques and compounds 4, 7 and 8 were found. The antibacterial activity of clerodane diterpenoids 1 and 2 and their metabolites 3-8 were also studied. The metabolites 3-7 showed moderate activities against both Gram-positive and Gram-negative organisms. While metabolite 8 showed a moderate activity against Gram-positive organisms and a good activity against Gram-negative organisms.

[4,4'-(Ethane-1,2-diyldinitrilo)-bis-(pent-2-en-2-olato)]copper(II) 0.25-hydrate.

In the title compound, [Cu(C(12)H(18)N(2)O(2))]·0.25H(2)O, the coordination of the O,N,N',O'-tetra-dentate ligand results in a cis-CuN(2)O(2) square-planar geometry for the metal ion and the presence of two six-membered and one five-membered chelate rings. The complete complex mol-ecule is close to planar (r.m.s. deviation = 0.047 Å). The uncoordinated water mol-ecule (O-atom site symmetry 2) was modelled as half occupied. In the crystal, C-H⋯O(w) and O(w)-H⋯O (w = water) hydrogen bonds link the components into layers parallel to ab plane.

Biologically active C-alkylated flavonoids from Dodonaea viscosa.

A new C-alkylated flavonoid (5,7-dihydroxy-3'-(4″-acetoxy-3″-methylbutyl)-3,6,4'-trimethoxyflavone (1), along with two known C-alkylated flavonoids (5,7-dihydroxy-3'-(3-hydroxymethylbutyl)-3,6,4'-trimethoxyflavone (2), 5,7,4'-trihydroxy-3'-(3-hyroxymethylbutyl)-3,6-dimethoxyflavone (3) and two new source C-alkylated flavonoids (5,7-dihydroxy-3'-(2-hydroxy-3-methyl-3-butenyl)-3,6,4'-trimethoxyflavone (4), 5,7,4'-trihydroxy-3,6-dimethoxy-3'-isoprenyl-flavone (5) were isolated from the aerial parts of Dodonaea viscosa. The structures of all compounds were established on the basis of 1D and 2D NMR spectroscopy and mass spectrometry. The isolated compounds were evaluated for their inhibitory effect on urease and α-chymotrypsin enzyme. All the compounds (1-5) exhibited mild inhibition against urease but remained recessive in case of α-chymotrypsin.

{5-Chloro-2-[(4-chloro-benzyl-idene)-amino]-phen-yl}(phen-yl)methanone.

In the title compound, C(20)H(13)Cl(2)NO, the C=N bond adopts an E conformation. The chloro-substituted rings form a dihedral angle of 11.99 (9)° with each other and form dihedral angles of 74.95 (9) and 83.26 (10)° with the unsubstituted ring. In the crystal, mol-ecules are connected into dimers by pairs of weak C-H⋯O hydrogen bonds and the dimers are arranged in columns parallel to the a axis.

N'-[(Z)-(1,5-Dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)methyl-idene]-2-hy-droxy-benzohydrazide.

In the title compound, C(19)H(18)N(4)O(3), the pyrazole ring is oriented at dihedral angles of 41.12 (7) and 12.25 (10)°, respectively, with respect to the planes of the phenyl and benzene rings. Intra-molecular N-H⋯O and O-H⋯O hydrogen bonds generate seven- and six-membered S(7) and S(6) ring motifs, respectively.

Methylenebissantin: a rare methylene-bridged bisflavonoid from Dodonaea viscosa which inhibits Plasmodium falciparum enoyl-ACP reductase.

A new methylene-bridged bisflavonoid, methylenebissantin (1), and nine known compounds, including flavonoids (2-5), diterpenoids (6 and 7), and phenol derivatives (8-10) were isolated from the aerial parts of Dodonaea viscosa Jacq. The structure elucidation was based on spectroscopic data analyses. The isolated compounds were evaluated for the inhibition of Plasmodium falciparum enoyl-ACP reductase (PfENR). Methylenebissantin (1) exhibited a moderate inhibition (IC(50) 91.13 µM) against PfENR.

Anti-inflammatory xanthones from the twigs of Hypericum oblongifolium wall.

Two new xanthonolignoids, hypericorin A (1) and hypericorin B (2), along with five known new source compounds, a xanthonolignoid, kielcorin (3), 4-hydroxy-2,3-dimethoxyxanthone (4), 3,4,5-trihydroxyxanthone (5), 1,3-dihydroxy-5-methoxyxanthone ( 6) and 1,3,7-trihydroxyxanthone (7), were isolated from the stems (twigs) of Hypericum oblongifolium Wall. The structures of the new compounds were deduced on the basis of spectroscopic techniques (EI-MS, HREI-MS, (1)H NMR, (13)C NMR, HMQC, HMBC, and NOESY). We also report herein for the first time the single crystal X-ray structure of compound 6. Compounds 1- 7 were screened for their IN VITRO anti-inflammatory (respiratory burst) inhibiting activities using isolated human neutrophils; compounds 1, 2, 3, 5, and 7 showed significant activities (IC (50) = 816.23 ± 73.30, 985.20 ± 55.80, 965.21 ± 65.80, 907.20 ± 50.80, 975.20 ± 81.10 µM, respectively), compound 6 showed moderate activity (IC (50) = 2500.85 ± 50.50 µM), while compound 4 was totally inactive at 1000 µg/mL as compared to the positive control used, indomethacin (IC (50) = 757.99 ± 5.90 µM), and aspirin (IC (50) = 279.44 ± 4.40 µM). Compound 4 was also inactive in comparison with other tested Hypericum compounds.

Dimethyl 2,2'-({2,2'-methyl-enebis[6-(2H-benzotriazol-2-yl)-4-(2,4,4-trimethyl-pentan-2-yl)-2,1-phenyl-ene]}di-oxy)diacetate.

The asymmetric unit of the title compound, C(47)H(58)N(6)O(6), comprises three independent mol-ecules, in one of which one tert-butyl group is disordered in a 1:1 ratio. The mol-ecule is a di(ar-yl)methane having two aliphatic and one N-heterocyclic substituent in each aryl ring. For the mol-ecule having the disordered tert-butyl group, the aryl rings make an angle of 115.3 (2)° at the methyl-ene carbon; one aryl ring is aligned at 42.0 (1)° with respect to the N-heterocyclic substituent and the other at 48.7 (1)° with respect to its substituent. The two ordered mol-ecules are disposed about a pseudo center of inversion. The pairs of twist angles in these two mol-ecules differ [52.7 (1) and 61.7 (1)°, and 29.1 (1) and 58.5 (1)°].

Bis[3-(2H-benzotriazol-2-yl)-2-(prop-2-yn-yloxy)-5-(2,4,4-trimethyl-pentan-2-yl)phen-yl]methane.

In the title compound, C(47)H(54)N(6)O(2), the C-C-C bond angle between the rings is 108.40 (13)°. One aryl ring aligned at 38.5 (1)° with respect to the N-heterocyclic substituent and the other at 56.0 (1)° with respect to its substituent. In the crystal, adjacent mol-ecules are linked by C-H⋯N hydrogen bonds, forming a chain extending along the a axis.