Dichloromethane Acetone Research Articles

Pyridine-2-olato bridged dirhodium(III) acyl organometallics: Synthesis, spectroscopic, structural and theoretical studies

The heterogeneous phase reaction of [Rh(MeLsb)(PPh3)2Cl2] (1) with the sodium salt of three different pyridine-2-olato ligands [Na(R‒Opy), R = H, Me, NO2] in dichloromethane–acetone–water medium afforded the complexes of type [Rh(Lal)(PPh3)(R-Opy)]2 (2(R)) in excellent yield. These are the first examples of dirhodium(III) acyl complexes with the bridging pyridine-2-olato ligand. The penta coordinated dirhodium(III) acyl complexes are formed by the cleavage of the RhCl and RhPPh3 bonds of the precursor complex 1. The two R-Opy ligands bridge the two rhodium centers through their OOpy donor centers. The conversion of 1→2(R) is attended with the concomitant hydrolysis of the aldiminium function in 1. The spectral (UV–vis, IR, NMR) data of the complexes are reported. The identity of 2(Me) has been established by single crystal X–ray structure determination which revealed distorted trigonal bipyramidal RhCNO2P coordination sphere. The Rh, C, N and Ophenolato atoms define the equatorial plane whereas Rh, OOpy and P atoms define the axial plane. The electronic structures and absorption spectra of the complexes are also scrutinized by the density functional theory (DFT) and time–dependent DFT calculations.

7-Acetoxyhorminone from Salvia multicaulis Vahl. as Promising Inhibitor of 3-Hydroxy-3-methylglutaryl Coenzyme A (HMG-CoA) Reductase.

3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase is a key enzyme involved in cholesterol biosynthesis and one of the most important targets for the treatment of hypercholesterolemia. A limited number of studies on the HMG-CoA reductase inhibitory potential of natural products are available. Thus, in the current study, we aimed to test the HMG-CoA reductase inhibitory capacity of extracts from the roots and aerial parts of Salvia multicaulis Vahl., through activity-guided isolation. Our findings revealed that the root extract prepared with dichloromethane–acetone (1:1) showed the highest inhibition (71.97 ± 0.37%) at 100 µg/mL. The extract was then initially fractionated by column chromatography and the obtained fractions were monitored by thin layer chromatography. Fractions which were similar to each other were combined and a total of 15 fractions were obtained. Further conventional chromatographic studies were carried out on the active fractions. Based on these fractions, 10 known compounds, comprising 9 terpenes and 1 steroid derivative in total, were isolated and their structures were verified by a combination of IT-TOF-MS, and 1D and 2D NMR techniques. According to the enzyme inhibition data of the identified compounds, 7-acetoxyhorminone exerted the highest inhibition (84.15 ± 0.10%, IC50 = 63.6 ± 1.21 µg/mL). The molecular docking experiments on 7-acetoxyhorminone and horminone indicated that both compounds strongly bind to the active site of the enzyme.

Extraction of Anthraquinones from Japanese Knotweed Rhizomes and Their Analyses by High Performance Thin-Layer Chromatography and Mass Spectrometry.

Anthraquinones (yellow dyes) were extracted from Japanese knotweed rhizomes with twelve extraction solvents (water; ethanol(aq) (20%, 40%, 60%, 70% and 80%), ethanol, 70% methanol(aq), methanol, 70% acetone(aq), acetone and dichloromethane). The obtained sample test solutions (STSs) were analyzed using high-performance thin-layer chromatography (HPTLC) coupled to densitometry and mass spectrometry (HPTLC–MS/MS) on HPTLC silica gel plates. Identical qualitative densitometric profiles (with anthraquinone aglycones and glycosylated anthraquinones) were obtained for STSs in all the solvents except for the STS in dichloromethane, which enabled the most selective extractions of anthraquinone aglycones emodin and physcion. The highest extraction efficiency, evaluated by comparison of the total peak areas in the densitograms of all STSs scanned at 442 nm, was achieved for 70% acetone(aq). In STS prepared with 70% acetone(aq), the separation of non-glycosylated and glycosylated anthraquinones was achieved with developing solvents toluene–acetone–formic acid (6:6:1, 3:6:1 and 3:3:1 v/v) and dichloromethane–acetone–formic acid (1:1:0.1, v/v). Non-glycosylated anthraquinones were separated only with toluene–acetone–formic acid, among which the best resolution between emodin and physcion gave the ratio 6:6:1 (v/v). This solvent and dichloromethane–acetone–formic acid (1:1:0.1, v/v) enabled the best separation of glycosylated anthraquinones. Four HPTLC-MS/MS methods enabled the identification of emodin and tentative identification of its three glycosylated analogs (emodin-8-O-hexoside, emodin-O-acetyl-hexoside and emodin-O-malonyl-hexoside), while only the HPTLC-MS/MS method with toluene-acetone-formic acid (6:6:1, v/v) enabled the identification of physcion. Changes of the shapes and the absorption maxima (bathochromic shifts) in the absorption spectra after post-chromatographic derivatization provided additional proof for the detection of physcion and rejection of the presence of chrysophanol in STS.

Pyridine-2-carboxylato chelated acylrhodium(III) organometallics: Spectroscopic, structural and theoretical studies

The heterogeneous phase reaction of Rh(MeLsb)(PPh3)2Cl2 (1) with the sodium salt of three differently substituted picolinate ligands [Na(R-pic), R = H, Me, Cl] in dichloromethane–acetone–water medium afforded the complexes of the type Rh(Lal)(PPh3)2(R-pic) (2(R)) in excellent yield. These are the first examples of acylrhodium(III) complexes with the picolinate ligand. The chelation of the picolinate ligand is attended with the cleavage of the two RhCl bonds and concomitant hydrolysis of the aldiminium function in 1. The picolinate ligand is coordinated to the rhodium center as bidentate N,O-donor forming five-membered chelate ring. The spectral (UV–Vis, IR, NMR) and electrochemical data of the complexes are reported. The identity of 2(H) has been established by single-crystal X-ray structure determination which revealed distorted octahedral RhCNO2P2 coordination sphere. The pairs (P,P), (C,O) and (O,N) define the three trans directions. The electronic structures and the absorption spectra of the complexes are also scrutinized by the density functional theory (DFT) and time-dependent DFT analysis.

Comparison of Single- and Sequential-Solvent Extractions of Total Extractable Benzo[ a]pyrene Fractions in Contrasting Soils.

The fate and behavior of polycyclic aromatic hydrocarbons (PAHs) in soil are of interest in the risk assessment of contaminated land and are usually based on determinations of fractions extracted from soil. For decades, either single- or sequential-solvent extractions have been used to determine PAH extractability in soils; however, there is a lack of certainty as to which fractions are being extracted by these techniques. This study is the first report of differences and similarities in the extractability of benzo[ a]pyrene (B[ a]P) in four contrasting soils (sandy loam, loamy sand, clayey loam, and sandy) when determined using both single-solvent (dichloromethane/acetone (DCM/Ace) mixture) and sequential-solvent (butanol followed by DCM/Ace) extraction. Residues after extraction were subjected to methanolic saponification (MeKOH). Butanol (BuOH) extractability and total extractability of B[ a]P following sequential-solvent extraction decreased significantly ( p < 0.05) with time after addition of B[ a]P. The decrease in BuOH extractability was particularly marked in the organic-matter-rich clayey-loam soil, which also had the largest (>40%) amounts of nonextractable residues. The cumulative amounts of B[ a]P extracted in each soil by single- and sequential-solvent extractions were similar ( p > 0.05) at each aging period, which indicated access to similar B[ a]P fractions in soil by both solvent extractions. The similarities in the amounts of B[ a]P nonextractable residues recovered by MeKOH from pre-extracted soils, through either of the extraction methods, confirms that the total extractable B[ a]P fractions from both methods are similar.

Characterization of phenolic compounds contained in bio-oil stemming from agricultural biomass wastes

Bio-oil is produced by biomass pyrolysis. It contains hundreds of chemical compounds including alkanes, aromatic hydrocarbons, esters, ethers, ketones, aldehydes, acids, alcohols, and phenols. Phenols are compounds of increasing interest; they can be used as feedstock in many industrial applications such as the production of fuel additives, chemical synthesis, or as food antioxidants. Therefore, the valorization of phenols stemming from bio-oil can be an appropriated alternative to reduce the dependence on petro-based phenols in the chemical industry. The most important phenols in biooil from agricultural wastes are phenol, guaiacol, cresols, syringol, and xylenol. These compounds were separated by silica gel column chromatography technique, using 3 different solvents: a dichloromethane—acetone mixture, ethyl acetate, and methanol. Column elution was followed by thin-layer chromatography (TLC). Phenolic fraction was obtained and not individual phenols. This fraction was analyzed using gas chromatography–f...

New jatrophane diterpenes from Euphorbia osyridea with proapoptotic effects on ovarian cancer cells

A dichloromethane–acetone extract of Euphorbia osyridea Bioss. (Syn. Euphorbia lateriflora Schumach. & Thonn), a spurge endemic to Iran and West Africa, afforded three new jatrophane diterpenes belonging to the 2,3,5,7,8,9,14,15-octahydroxy-jatropha-6(17),11E-diene class along with three known triterpenes. Structures of these compounds were elucidated by spectroscopic methods, especially 2D NMR analyses. Biological effects of these compounds were analyzed by performing MTT and annexin V-FITC and PI staining assays against different cancer cell lines. Results showed that 2,3,5,7,8,9,14,15-octahydroxy-jatropha-6(17), 11E-diene derivatives (1–3) inhibit the cell proliferation through apoptosis in the Caov-4 and OVCAR-3 cancer cell lines.

Homochiral l-prolinamido-sulfonamides and their use as organocatalysts in aldol reactions

The synthesis of new homochiral l-prolinamido-sulfonamides 1–7 from enantiomerically pure (R,R)-11,12-diamino-9,10-dihydro-9,10-ethanoanthracene (R,R)-8 is reported. The l-prolinamido-sulfonamides 1–7 were tested as organocatalysts (10mol%) in the aldol reaction of p-nitrobenzaldehyde and acetone in dichloromethane at room temperature in the presence of water (1equiv) and acetic acid (20mol%) giving good to high yields and enantioselectivities. Catalyst 4 (10mol%) afforded the best results in the aldol reaction of acetone with p-substituted-benzaldehydes with electron withdrawing groups (i.e., nitro, cyano, bromo and chloro, up to 97% yield and 90% ee). The origin of the enantioselective induction was modeled using DFT methods. The estimated enantioselectivity for the model system is consistent with the experimental data.

Chemical Constituents of Cinnamomum iners

Cinnamomum iners, a species closely similar to C. subcuneatum Miq., is an evergreen medium height tree with reddish brown and smooth branchlets. Cinnamomum iners is widely distributed in Southeast Asia from Indochina, Sumatra, Pensular Malaysia, Java, and the Philippines [1]. Previous studies reported the presence of -caryophyllene, stigmasterol, cardiac glycoside, flavonoid, polyphenol, saponin, sugar, tannin and terpenoid in the tree [2]. This study was conducted as part of our research on the chemical constituents of Cinnamomum species found in the Philippines. We earlier reported the isolation of a new monoterpene natural product and a new sesquiterpene, along with the known compounds 4-hydroxy-3-methoxycinnamaldehyde, 4-allyl-2-methoxyphenol, -terpineol, and humulene from the bark of C. cebuense, while the leaves afforded humulene, -caryophyllene, squalene, and a mixture of -amyrin, -amyrin, and bauerenol [3]. We also reported the presence of 1 ,4 ,7 -trihydroxyeudesmane, 4 -hydroxy-5,7,3 -trimethoxyflavan-3-ol, squalene, polyprenol, and a mixture of -amyrin, -amyrin, and bauerenol from the dichloromethane (DCM) extract of the bark of C. griffithii, and squalene and benzyl benzoate from the leaves [4]. Silica gel chromatography of the DCM extract of the bark of C. iners from Guimaras Island, Philippines afforded 5,7-dimethoxy-3 ,4 -methylenedioxyflavan-3-ol (1) and -sitosterol (2), which were also obtained from the DCM extract of the twigs of C. iners together with 4-(4-hydroxy-3-methoxyphenyl)but-3-en-2-one (3), cinnamaldehyde (4), linoleic acid (5), and vanillin (6). The leaves of C. iners afforded eugenol (7), linoleic acid (5), and -sitosterol (2). The structures of 1, 3, and 4 were elucidated by extensive 1D and 2D NMR spectroscopy and confirmed by comparison of their 13C NMR data with those reported in the literature for 5,7-dimethoxy-3 ,4 -methylenedioxyflavan-3-ol [5], 4-(4-hydroxy-3-methoxyphenyl)but-3-en-2-one [6], and cinnamaldehyde [7], respectively. The structures of -sitosterol (2) [8], linoleic acid (5) [9], vanillin (6) [10], and eugenol (7) [11] were confirmed by comparison of their 13C NMR data with those reported in the literature. The bark and leaves of Cinnamomum iners were collected from Guimaras, Philippines in May 2011. Voucher specimens were authenticated by one of the authors (EMGA) and deposited in the De La Salle University-Manila Herbarium (DLSU3103). The bark of C. iners was chopped into small pieces and then air dried. The air-dried bark (313.3 g) was soaked in DCM for 3 days and then filtered. The filtrate was concentrated under vacuum to afford the crude extract (7.1 g), which was chromatographed in increasing proportions of acetone in DCM at 10% increments as eluents. The 10% acetone in DCM fraction from the chromatography of the crude extract was rechromatographed (3 ) in 1% ethyl acetate in petroleum ether, then (2 ) in 2.5% ethyl acetate in petroleum ether to afford 2 (25.0 mg). The 20% acetone in DCM fraction was rechromatographed (5 ) in 5% ethyl acetate in petroleum ether, then (3 ) in 7.5% ethyl acetate in petroleum ether as eluents to afford 1 (12.0 mg). The air-dried twigs of C. iners (112.9 g) were ground in an osterizer, soaked in DCM for 3 days, and then filtered. The filtrate was concentrated under vacuum to afford the crude extract (1.6 g), which was chromatographed in increasing proportions of acetone in DCM at 10% increments as eluents. The DCM fraction from the chromatography of the crude extract was rechromatographed (6 ) in petroleum ether to afford 4 (10.0 mg). The 20% acetone in DCM fraction was rechromatographed (3 ) in 15% ethyl acetate in petroleum ether, then (3 ) in DCM as eluents. The less polar fractions yielded 2 (15.0 mg), while the more polar eluents afforded 3 (12.0 mg). The 30% acetone in DCM and 40% acetone in DCM

Chemical Constituents of Cinnamomum rupestre and Cinnamomum nanophyllum

Cinnamomum rupestre Kosterm. (Lauraceae) is an endemic species in the Philippines originally discovered in Palawan [1], while Cinnamomum nanophyllum Kosterm. is a widespread endemic species in the country. In Cebu, the local people collect and prepare the leaves and the bark as a decoction for relief of stomach and abdominal ailments. There are no reported chemical and biological studies on C. rupestre and C. nanophyllum. These are two of the 21 species of Cinnamomum found in the Philippines, of which 16 are known to be endemic [1]. This study was conducted as part of our research on the chemical constituents of Cinnamomum species found in the Philippines. We earlier reported the isolation of eugenol and safrole from the bark, polyprenol from the leaves, and trilinolein from the roots of Cinnamomum cebuense [2]. Silica gel chromatography of the dichloromethane (DCM) extract of the bark of C. rupestre afforded 4 -hydroxy5,7,3 -trimethoxyflavan-3-ol (1), 4-hydroxy-3-methoxycinnamaldehyde (2), and 4-allyl-2-methoxyphenol or eugenol (3), while the leaves yielded -sitosterol (4). The structure of 1 was elucidated by extensive 1D and 2D NMR spectroscopy and confirmed by comparison of its 13C NMR data with those reported in the literature for 4 -hydroxy-5,7,3 -trimethoxyflavan-3-ol (1) [3]. The structures of 4-hydroxy-3-methoxycinnamaldehyde (2) [4], 4-allyl-2-methoxyphenol or eugenol (3) [5], and -sitosterol (4) [6] were confirmed by comparison of their 13C NMR data with those reported in the literature. The DCM extract of the bark of C. nanophyllum afforded 1, 2, 4, and trilinolein (5), while the leaves yielded 4. The structure of trilinolein (5) [7] was confirmed by comparison of its 13C NMR data with those reported in the literature. To the best of our knowledge, this is the first report on the chemical constituents of C. rupestre and C. nanophyllum. The bark and leaves of Cinnamomum rupestre and Cinnamomum nanophyllum were collected from Hagnaya, Carmen, Cebu, Philippines in June 2010. Voucher specimens of Cinnamomum rupestre and Cinnamomum nanophyllum were authenticated by one of the authors (EMGA) and deposited in the De La Salle University-Manila Herbarium (DLSU-3101 and DLSU-3102, respectively). The air-dried bark and leaves of C. rupestre were chopped into small pieces and then air dried. The air-dried bark (371.8 g) and leaves (89.1 g) were soaked in DCM for 3 days and then filtered. The filtrates were concentrated under vacuum to afford the crude extracts of bark (16.6 g) and leaves (7.0 g), which were fractionated by silica gel chromatography using increasing proportions of acetone in DCM (10% increment by volume) as eluents. The DCM fraction from the bark was rechromatographed in petroleum ether (7 ) to afford 3 (28 mg). The 30% acetone in DCM fraction was rechromatographed with 12.5% ethyl acetate in petroleum ether as eluent to afford 2 (18 mg). The 40% acetone in DCM fraction was rechromatographed (5 ) in DCM, then (8 ) in diethyl ether–acetonitrile–DCM (0.5:0.5:9) to afford 1 (12 mg). The DCM fraction from the leaves was rechromatographed (3 ) in 5% ethyl acetate in petroleum ether to afford 4 (10 mg). The air-dried bark and leaves of C. nanophyllum were chopped into small pieces and then air dried. The air-dried bark (493.5 g) and leaves (49.5 g) were soaked in DCM for three days and then filtered. The filtrates were concentrated under vacuum to afford the crude extracts of bark (8.0 g) and leaves (9.5 g), which were fractionated by silica gel chromatography using increasing proportions of acetone in DCM (10% increment by volume) as eluents. The crude DCM extract of the bark of C. nanophyllum was chromatographed in increasing proportions of acetone in DCM at 10% increment as eluents. The 10%

Terpenoids from Ardisia squamulosa

The genus Ardisia Swartz belongs to the family Myrsinaceae. Ardisia has 68 recorded species in the Philippines [1], 60 of which are endemic. The hexane extract from A. squamulosa was reported to have a significant effect on sperm count but has a negligible effect on sperm morphology and viability [2]. No chemical study of A. squamulosa has been reported. However, we earlier studied a congener of this plant, Ardisia pyramidalis, which afforded spinasterol, spinasteryl acetate, a mixture of -amyrin, -amyrin and bauerenol, squalene, lutein, and triglycerides from the dichloromethane (DCM) extract of the leaves. Spinasterol was found to exhibit anti-angiogenic potential [3]. This study was conducted as part of our research on the chemical constituents of Ardisia species found in the Philippines. We report herein the chemical constituents of the DCM extract of the leaves of A. squamulosa. Fresh leaves of Ardisia squamulosa were collected from Kanawan, Morong Bataan, Philippines in 2010 by Ramon Bandong. The sample was authenticated by the Jose Vera Herbarium Collection at the Institute of Biology of the University of the Philippines-Diliman and the Philippine National Museum, Manila. The DCM extracts of the air-dried leaves of A. squamulosa afforded terpenoids by silica gel chromatography. These compounds were identified by comparison of their 13C NMR data with those of -caryophyllene (1) [4], squalene (2) [5], bauerenone (3a) [6], ursenone (3b) [7], oleanone (3c) [7], bauerenol (4a) [6], -amyrin (4b) [8], -amyrin (4c) [8], and lutein (5) [9] reported in the literature. Air-dried leaves of Ardisia squamulosa (1 kg) were ground in an Osterizer and then soaked in DCM for three days and filtered. The filtrate was concentrated in vacuo to afford a crude extract (55 g), which was chromatographed in increasing proportions of acetone in dichloromethane at 10% increment. The DCM fraction was rechromatographed (6 ) in petroleum ether to afford 1 (5 mg) and 2 (20 mg). The 10% acetone in DCM and 20% acetone in DCM fractions were combined and rechromatographed (4 ) with 2.5% ethyl acetate in petroleum ether as eluent to afford a mixture of 3a–3c (12 mg). The 30% acetone in DCM fraction was rechromatographed (5 ) using 5% ethyl acetate in petroleum ether to afford a mixture of 4a–4c (15 mg). The 40% acetone in DCM and 50% acetone in DCM fractions were combined and rechromatographed (3 ) with DCM–diethyl ether–acetonitrile (9:0.5:0.5) as eluent to afford 5 (18 mg) after washing with diethyl ether.

Spectrophotometric and spectroscopic studies of charge transfer complexes of p-toluidine as an electron donor with picric acid as an electron acceptor in different solvents

The charge transfer complexes of the donor p-toluidine with π-acceptor picric acid have been studied spectrophotometrically in various solvents such as carbon tetrachloride, chloroform, dichloromethane acetone, ethanol, and methanol at room temperature using absorption spectrophotometer. The results indicate that formation of CTC in non-polar solvent is high. The stoichiometry of the complex was found to be 1:1 ratio by straight-line method between donor and acceptor with maximum absorption bands. The data are discussed in terms of formation constant ( K CT), molar extinction coefficient ( ɛ CT), standard free energy (Δ G o), oscillator strength ( f), transition dipole moment ( μ EN), resonance energy ( R N) and ionization potential ( I D). The results indicate that the formation constant ( K CT) for the complex was shown to be dependent upon the nature of electron acceptor, donor and polarity of solvents that were used.

Studies on chemical constituents of Gracilaria verrucosa

A new sterol glucoside, (24R)-5α-stigmast-9-(11)-en-3β-D-glucopyranoside (1) has been isolated from a methanol extract of the red alga Gracilaria verrucosa, while cholesterol and (Z)-9-hexadecenoic acid (palmitoleic acid) have been isolated from a dichloromethane–acetone extract of the same alga. Additionally, an oily fraction of a dichloromethane–acetone extract has been investigated by gas chromatography/mass spectrometry (GC/MS). The main components in the oily fraction were heneicosanoic acid (49.8%), (Z)-9-octadecenoic acid (15.8%), and 15-tetracosenoic acid (15.6%) in addition to a few hydrocarbons, simple aromatics and a new compound, namely 3,4-dimethyl-5-carboxyclic acid-1-oxacyclopent-3-en-2-one. The structures of the isolated compounds have been elucidated by spectroscopic methods.

Aluminum Compounds Containing η1‐ and/or η5‐Bidentate Dianionic Pyrrolyl–Methylamide Ligands

A series of dialuminum compounds have been synthesized and their reactivity and application for lactide polymerization have been studied. The reaction of AlH3 x NMe3 with [C4H3NH(2-CH2NHtBu)] in diethyl ether generated a dimeric aluminum hydride compound, [[[C4H3N(2-CH2NtBu)]AlH]2] (1). The structure of 1 was confirmed by spectroscopy of a deuterated analogue of 1 with an Al--D function. Direct treatment of [C4H3NH(2-CH2NHtBu)] with LiAlH4 in diethyl ether resulted in colorless crystals of [[Li[micro-eta1:eta5-C4H3N(2-CH2NtBu)]2Al]2] (2) in 80 % yield after recrystallization from a toluene solution. The micro-eta1:eta5-pyrrolyl protons exhibit high-field shifts at delta=5.73, 6.15, and 6.72 comparable to a similar eta5-bonding mode in the literature. Treatment of 1 with 1 equiv acetone oxime or acetone in dichloromethane gave [[[C4H3N(2-CH2NtBu)]Al[varkappaO,varkappaN-(ON==CMe2)]]2] (3) and [[[C4H3N(2-CH2NtBu)]Al(O--CHMe2)]2] (4) in 67 % and 60 % yield, respectively. Compounds 1-4 have been characterized by X-ray diffractometry and were used as catalysts for epsilon-caprolactone polymerization.

Separation of Organic Compounds by Gradient Simulated Moving Bed Chromatography

A promising solution for the separation of organic compounds in pharmaceutical industry is the gradient simulated moving bed chromatography (SMB). The above mentioned process can be used for the production of high purity materials (isomers, optical isomers, biomolecules). We assumed isotherm, isochor equilibrium adsorption (competitive multicomponent Langmuir-adsorption equilibrium) in the mathematical model and neglected the effects of axial dispersion. In our present work we extended the mathematical model with solvent adsorption-desorption processes (acetone-dichloromethane eluent, steroid compounds, silicagel). The mathematical model was solved by finite differences numerical mathematical method using PC. The gradient SMB separations were carried out with a laboratory scale four column equipment in open loop system at 1:1:2:0 column configuration. The SMB equipment (L=25 cm, I.D.=1 cm) was planned and constructed for separation of a steroid mixture using YMC S-50 silica gel as adsorbent (specific surface=798.63 m g). The effect of switching time change (5.5 min, 9 min, 11.5 min, 22.5 min) on component separation was examined. During our measurements the amount of acetone in dichloromethane was 55 % v/v in the fresh eluent and pure dichloromethane in the feed. The process variables of the gradient SMB (product purity, yield, productivity, specific solvent consumption) are very favourable. Our conclusion is that the measured and the calculated data agree well and we have produced more than 99.9 %m/m purity and 90 % yield , productivity 1300-3000 g steroid kg adsorbent day at 0.1-0.3 m fresh eluent kg steroid eluent consumption.

Generalised method for the determination of heterogeneous batch distillation regions

A new, general method for the calculation of residue curves and for the determination of batch distillation regions of heteroazeotropic distillation is suggested. The method proposed, which means the extension of the method of Pham and Doherty, takes into consideration the possibility of the withdrawal of any fraction of either liquid phase from the decanter as distillate. The simplified and rigorous simulation calculations were carried out for the mixtures dichloromethane–acetone (low α ) + water (heavy, selective, heterogeneous entrainer), water–ethylenediamine (maximum azeotrope) + benzene (light, selective, heterogeneous entrainer) and isopropanol–water (minimum azeotrope) + benzene (light, non-selective, heterogeneous entrainer). The new method gives the right sequence of the cuts for all operation modes and strategies of heterogeneous batch distillation.

Preparation of roxithromycin-polymeric microspheres by the emulsion solvent diffusion method for taste masking

Microspheres of roxithromycin with Eudragit S100 and silica were prepared by the emulsion solvent diffusion method to mask the bitter taste of the antibiotic. The effect of different polymers and drug–polymer ratios on the taste masking and the characteristics of the microspheres were investigated. It was found that Eudragit S100 was the best for masking the unpleasant taste of roxithromycin among the six kinds of polymers investigated. The results of DSC, X-ray diffraction and IR showed that there were several combinations of roxithromycin and Eudragit S100. The influence of other formulation factors, i.e. dichloromethane–acetone ratios and silica–polymer ratios on the properties of the microspheres were also examined. In conclusion, the results of the present study will be helpful for the preparation of oral forms of roxithromycin with an acceptable taste.

Temporal variations in PAH concentrations in Quercus ilex L. (holm oak) leaves in an urban area

Temporal variations of polycyclic aromatic hydrocarbon (PAH) concentrations in leaves of a Mediterranean evergreen oak, Quercus ilex L., were investigated in order to assess the suitability of this species to biomonitor PAH air contamination. Leaf samples were collected at six sites of the urban area of Naples (Italy) and at a control site in the Vesuvius National Park, in May and September 2001, and in January and May 2002. PAH extraction was conducted by sonication in dichloromethane–acetone and quantification by GC–MS. In winter, leaf total PAH concentrations showed, at all the urban sites, values 2-fold higher than in all the other samplings, reflecting the temporal trend reported for PAH air contamination in the Naples urban area. Moreover, leaf PAH concentrations showed, at all the urban sites, a decrease in May 2002 after the winter accumulation. At the control site leaf PAH concentrations showed lower values and smaller temporal variations than at the urban sites. The findings support the suitability of Q. ilex leaves to monitor temporal variations in PAH contamination. The highest winter concentrations of total PAHs were due to the medium molecular weight PAHs that increased with respect to both low and high molecular weight PAHs. The medium molecular weight PAHs showed the same temporal trend both at the urban and remote sites.

Study of Open–looped Simulated Moving Bed (SMB) Chromatographic Process

In this experimental work laboratory scale four-column simulating moving bed (SMB) equipment (L=25 cm, ID=1 cm) was planned and constructed for separation of a steroid mixture [1] using YMC S-50 silica gel as adsorbent, with the co-operation of Central Mechanical Workshop, University of Veszprem. The effect of switching time change (5.5 min, 9 min, 11.5 min, 22.5 min) on component separation was examined. During our measurements the amount of acetone in dichloromethane was 55 % v/v in the fresh eluent and pure dichloromethane in the feed. Product purity and other specifications (yield, productivity, eluent consumption) were measured by gas chromatography. An equilibrium mathematical model of the SMB process for open and closed eluent loops was constructed by means of a computer program [2, 3]. Adsorption equilibrium, and kinetic data, theoretical plate number measurement, frontal and elution adsorption-desorption measurements for determination of the optimum conditions for the SMB process and for construction of the mathematical model were measured by means of laboratory experiments. Finally results coming from simulation program were compared to measurement results. Our conclusion is that the measured and the calculated data agreed well and we have produced more than 99.9 % m/m purity and 90 % yield, at productivity 1300-3000 g “B” component/ kg adsorbent within a day using 60 g dm inlet steroid composition in case of 1:1:2:0 column configuration.

Batch heteroazeotropic rectification of a low α mixture under continuous entrainer feeding

AbstractThe separation of a low‐relative‐volatility, zeotropic mixture in a batch rectifier with a selective entrainer was studied by feasibility and rigorous simulation calculations. The entrainer is the high boiler in the system and forms a binary heteroazeotrope with the low‐boiler component. Beside the traditional batch addition, the continuous feeding of the entrainer was also investigated. The feasibility of the heteroazeotropic distillation in a batch rectifier was assessed by a new method, extending the methods published for the batch homoazeotropic distillation. The method is based on the analysis of the map of the possible overall liquid composition profiles, which also contains the heterogeneous liquid boiling envelope. The results obtained for batch addition and continuous feeding of the entrainer are compared. The influence of the most important operational parameters is also studied. The results are presented for the dichloromethane–acetone mixture by using water as a heterogeneous entrainer.