Alumina modified by dimethyl sulfoxide as a new selective solid phase extractor for separation and preconcentration of inorganic mercury(II)

Dimethyl sulfoxide (DMSO) was simply immobilized to neutral alumina via quite strong hydrogen bonding between sulfoxide oxygen and surface alumina hydroxo groups. The produced alumina-modified dimethyl sulfoxide (AMDMSO) solid phase (SP)-extractor experienced high thermal and medium stability. Moreover, the small and compact size of DMSO moiety permit high surface coverage evaluated to be 2.1 ± 0.1 mmol g⁻¹ of alumina. Hg(II) uptake was 1.90 mmol g⁻¹(distribution coefficient log K_d = 5.658) at pH 1.0 or 2.0, 1.68 mmol g⁻¹ (log K_d = 4.067) at pH 3.0 or 4.0 while the metal ions Ca(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) showed low values 0.513-0.118 mmol g⁻¹ (log K_d < 3.0) in the pH range 4.0-7.0. A mechanism was suggested to explain the unique uptake of Hg(II) ions by binding as neutral and chloroanionic species predominate at pH values ≤ 3.0 of a medium rich in chloride ions. A direct and fast batch separation mode was achieved successfully to retain selectively Hg(II) in presence of other eight coexisting metal ions. Thus, Hg(II) was completely retained; Ca(II), Co(II), Ni(II) and Cd(II) were not retained, while Pb(II), Cu(II), Zn(II) and Fe(III) exhibited very low percentage retention evaluated to be 0.42, 0.49, 1.4 and 5.43%, respectively. The utility of the new modified alumina sorbent for concentrating of ultratrace amounts of Hg(II) was performed by percolating 2 l of doubly distilled water, drinking tap water, and Nile river water spiked with 10 ng/l over 100 mg of the sorbent packed in a minicolumn used as a thin layer enrichment bed prior to the determination by CV-AAS. The high recovery values obtained (98.5 ± 0.5, 98.5 ± 0.5 and 103.0 ± 1.0) based on excellent enrichment factor 1000, along with a good precision (R.S.D.% 0.51-0.97%, N = 3) demonstrate the accuracy and validity of the new modified alumina sorbent for preconcentrating ultratrace amounts of Hg(II) with no matrix interference.     

Composition, structure and solution properties of polysaccharides extracted from leaves of Mesembryanthenum crystallinum

Water and Chelator-soluble polymers were independently isolated from the alcoholic-insoluble substance (AIS) of Mesembryanthenum crystallinum leaves. After precipitation in ethanol and ultrafiltration (40 kD cut-off) of recovered solids dissolved in water, the yield relative of the so-call Lw and LCh polymers to the AIS dry matter was 2.5 ± 0.2 and 7 ± 0.5%. The galacturonic acid contents were 67 ± 3% and 63 ± 5%. The degrees of methylesterification of ca. 45 ± 3% and 50 ± 3%, showed that Lw and LCh belonged to the fairly methylesterified pectin class. From sugar analysis, LCh was shown to contain at least two types of pectic blocks, homogalacturonan (HG: 58%) and rhamnogalacturonan-I (RG-I: 34%). Their structure were deduced after saponification, polygalacturonase treatments, size exclusion chromatography (SEC) onto Sephacryl S-200 and then sugar composition of the collected fractions. The main polymers were methylesterified HG (32%), some of them being linked to non-methylesterified HG (10%), and to polygalacturonase-resistant HG (17%). In addition, there were (1) a highly soluble RG-I with long galactan side chains (RG-I-gal accounting for 9%) and (2) a RG-I with short arabino-galactan side chains (25%), named RG-I-ara/gal that was almost totally lost during SEC analysis, due to its low solubility at room temperature and in absence of chelators.SEC coupled with differential refractive index and light scattering showed that highly methylesterified HG chains exhibited aggregate structures in solution due to intermolecular hydrophobic interactions. These interactions formed hydrophobic clusters, which have been characterized by surface tension measurements and with a polarity probe, the Coomassie Brilliant Blue dye. After alkaline treatment of LCh, the self-assembly of HG disappeared.     

Advancements in synthesis of pharmacologically active imidazolidin-4-ones and stereochemistry of their Reactions with some Reagents

1-Aryl, 1,3-diaryl- and 5-(2-oxo-2-arylethyl)-2-thioxo-imidazolidin-4-ones 2 were prepared as before, nevertheless, equivalent amounts of potassium hydroxide were added to the reaction conditions. This change, dramatically, reduced the reaction time and highly increased the yield of some derivatives. Treatment of 2 with sulfuric acid converted them into their analogous (E)/(E,Z)-5-(2-oxo-2-arylethylidene) derivatives 3 . Reactions of 2 and/or 3 with chromium trioxide affected their conversion into the corresponding 2,4-diones 4 and 5 , respectively. Treatment of 2 and/or 3 with ethyl bromoacetate affected conversion of the former into their respective 2,4-diones 4 , whereas it gave the respective 2-alkylthio derivatives of the latter. Reactions of 2b with aromatic aldehydes gave mixtures of spiro-1H- and 2H-pyrrole diastereomers. Structures of the new products were evidenced by infrared, EI-MS, ¹H- and ¹³C-NMR spectroscopic measurements. Many of the selected compounds showed good antimicrobial activity.     

Synthesis,reactions, and antimicrobial activity of 2-cyano-N′-(4-(2-oxo-2-phenylethoxy)benzylidene)acetohydrazide derivatives

Knӧvenagel condensation of the starting 2-cyano-N′-(4-(2-oxo-2-phenylethoxy)-benzylidene)acetohydrazide with different aromatic aldehydes produced the comparable arylidenes derivatives. Else way, 2-cyano-N′-(4-(2-oxo-2-phenylethoxy)-benzylidene)-acetohydrazide condensed with o-hydroxybenzaldehydes affording the respective chromenes which latter underwent acid hydrolysis giving the oxo-chromenes analogues. Moreover, the reaction of 2-cyano-N′-(4-(2-oxo-2-phenylethoxy)benzylidene)acetohydrazide with istain yielded the respective indeno[2,1-b]furan derivative that was converted to its oxo-analogue through acid hydrolysis. The treatment of 2-cyano-N′-(4-(2-oxo-2-phenylethoxy)benzylidene)acetohydrazide with α-halocompounds produced the relevant thiazoles. The enamine 2-cyano-3-(dimethylamino)-N′-(4-(2-oxo-2-phenylethoxy)benzylidene)acrylohydrazide underwent nucleophilic substitution reaction with guanidine hydrochloride followed by heterocyclization to get the relative aminopyrimidine. Contrarily, the reaction with various 4-arylazo-3,5-diaminopyrazoles provided the relative pyrazolo[1,5-a]pyrimidines. The antimicrobial investigation was carried out for some of the newly synthesized compounds using agar well diffusion method.     

Synthesis,antimicrobial and anticancer activities of some new N-methylsulphonyl and N-benzenesulphonyl-3-indolyl heterocycles: 1st Cancer Update

A series of 1-(N-methyl 2a–c and N-benzenesulphonyl-1H-indol-3-yl)-3-aryl-prop-2-ene-1-ones 3a–c were prepared and allowed to react with urea, thiourea or guanidine and gave the pyrimidine derivatives 4a–c to 9a–c. Base catalyzed reaction of 2a–c or 3a–c with ethyl acetoacetate gave cyclohexanone derivatives 10a–c and 11a–c, respectively. Reaction of the latter compounds with hydrazine hydrate afforded indazole derivatives 12a–c and 13a–c, respectively. On the other hand, condensation of 2c or 3c with some hydrazine derivatives namely, hydrazine hydrate, acetyl hydrazine, phenyl hydrazine and benzyl hydrazine hydrochloride gave pyrazole derivatives 14a,b-17a,b, respectively. Moreover, reaction of 2c or 3c with hydroxyl amine hydrochloride gave isoxazole derivatives 18a,b. The newly synthesized compounds were tested for their antimicrobial activity and showed that, compounds 14a, 14b, 15a and 15b were found to be the most active ones of all the tested compounds toward Salmonella typhimurium (ATCC 14,028) compared to the reference drug chloramphenicol. Eighteen new compounds namely, pyrimidin-2(1H)-ones 4a–c and 5a–c, pyrimidin-2(1H)-thiones 6a–c and 7a–c and pyrimidin-2-amines 8a–c and 9a–c were tested for their in vitro cytotoxicity against human liver carcinoma (HEPG2), human breast cancer (MCF7) and human colon cancer (HCT-116) cell lines and showed that, compounds 4c, 5c, 6c, 8c and 9c were found to be the highly active compounds compared to the reference drug doxorubicin.     

Antioxidant properties of phenolic Schiff bases: structure–activity relationship and mechanism of action

Phenolic Schiff bases are known for their diverse biological activities and ability to scavenge free radicals. To elucidate (1) the structure–antioxidant activity relationship of a series of thirty synthetic derivatives of 2-methoxybezohydrazide phenolic Schiff bases and (2) to determine the major mechanism involved in free radical scavenging, we used density functional theory calculations (B3P86/6-31+(d,p)) within polarizable continuum model. The results showed the importance of the bond dissociation enthalpies (BDEs) related to the first and second (BDE_d) hydrogen atom transfer (intrinsic parameters) for rationalizing the antioxidant activity. In addition to the number of OH groups, the presence of a bromine substituent plays an interesting role in modulating the antioxidant activity. Theoretical thermodynamic and kinetic studies demonstrated that the free radical scavenging by these Schiff bases mainly proceeds through proton-coupled electron transfer rather than sequential proton loss electron transfer, the latter mechanism being only feasible at relatively high pH.     

A Comprehensive Analysis Using Colorimetry,Liquid Chromatography-Tandem Mass Spectrometry and Bioassays for the Assessment of Indole Related Compounds Produced by Endophytes of Selected Wheat Cultivars

Liquid chromatography–tandem mass spectrometry (LC–MS/MS), colorimetry, and bioassays were employed for the evaluation of the ability of endophytic bacterial strains to synthesize indole-related compounds (IRCs) and in particular indole-3-acetic acid (IAA). A total of 54 endophytic strains belonging to seven bacterial genera isolated from tissues of common and spelt wheat cultivars were studied. The endophytic bacteria isolated from different tissues of the tested wheat types were capable of IRCs production, including IAA, which constituted from 1.75% to 52.68% of all IRCs, in in vitro conditions via the tryptophan dependent pathway. The selected post-culture medium was also examined using a plant bioassay. Substantial growth of wheat coleoptile segments treated with the bacterial post-culture medium was observed in several cases. Our data suggest that the studied endophytic bacteria produce auxin-type compounds to support plant development. Summarizing, our approach to use three complementary methods for estimation of IRCs in different endophytic strains provides a comprehensive picture of their effect on wheat growth.     

Vector extrapolation enhanced TSVD for linear discrete ill-posed problems

The truncated singular value decomposition (TSVD) is a popular solution method for small to moderately sized linear ill-posed problems. The truncation index can be thought of as a regularization parameter; its value affects the quality of the computed approximate solution. The choice of a suitable value of the truncation index generally is important, but can be difficult without auxiliary information about the problem being solved. This paper describes how vector extrapolation methods can be combined with TSVD, and illustrates that the determination of the proper value of the truncation index is less critical for the combined extrapolation-TSVD method than for TSVD alone. The numerical performance of the combined method suggests a new way to determine the truncation index. In memory of Gene H. Golub.