Normal Silica Gel Research Articles

Bio-screening and quantification of methyl paraben in vinegar and coconut juice separated by HPTLC

As a widely used food preservative, methyl paraben was experimentally evidenced with serious hormone-like adverse effects. Herein, a high performance thin-layer chromatography platformed bioluminescent bioautography and image analysis for the selective quantification and confirmation of methyl paraben was proposed and validated in vinegar and coconut juice. First, the detectability of the bioautography to the analyte on different layer materials was estimated, revealing that normal silica gel was the best choice. After that, the liquid of sample extract and working solution were separated to overcome the background noises due to co-extracted matrices. The separation result was then coupled to the optimized bioautography, enabling instant and straightforward screening of the targeted compound. For accurate quantification, bioluminescent inhibition pattern caused by the analyte was processed by image analysis, giving useful sensitivity (LOD > 16 mg/kg), precision (RSD < 10.1 %) and accuracy (spike-recovery rate 76.9 %–112.2 %). Finally, the suspected result was confirmed by determining its MS fingerprint, further strengthening the reliability of screening.

EXPLORING THE ANTIDIABETIC AND ANTIOXIDANT POTENTIAL OF NEPETA ADENOPHYTA HEDGE IN HEPG2 CELLS AND ITS PHYTOCHEMICAL STUDIES

The current study is based on the phytochemical isolation and biological activity evaluation of Nepeta adenophyta Hedge. This plant species is traditionally used for abdominal pain, kidney pain, stomach problems, urine problems, and diarrhea and is examined to control bleeding. Five compounds were isolated using column chromatography over normal silica gel from the ethanolic crude extract of Nepeta adenophyta and their structures were characterized with the help of spectroscopic techniques. In addition, the crude extract was evaluated for its antioxidant and antidiabetic potential in a human hepatoma cell line HepG2 cells and the crude extract showed good activities. The phytochemical isolation studies and the biological activities are conducted for the first time on the study sample.

Chemical Composition and Antimicrobial Effect of Western Ethiopian Propolis.

Propolis or bee glue is commonly named as a natural resinous mixture produced by honeybees (Apis mellifera) from substances collected from parts of plants, buds, and exudate. The result of the ethyl acetate - methanol (3 : 2) volume by volume fraction yielded a total of two compounds namely betulinic acid and β-amyrin isolated from Bodji Dirmaji and Fincha'a district propolis, respectively. The crude ethanolic extract was portioned with the different solvent systems by increasing the polarities in the following order of hexane, ethyl acetate, and methanol. Column chromatographic method on normal silica gel was used to isolate the compounds. The structures of the compounds were characterized using 1D NMR techniques. The study revealed that western Ethiopian propolis was rich in saponins, tannins, flavonoids, steroids, triterpenes, and glycosides. The antibacterial activity for the isolated compound (betulinic acid) showed the highest inhibition for S. aureus (11.2±1.6), E. coli (17.7±1.1), and A. niger (12.6±1.2) mm.

Quantum dot decorated polyaniline plastic as a multifunctional nanocomposite: experimental and theoretical approach.

AgO, CoO, and ZnO (ACZ) mixed metal quantum dots (QDs) were synthesized by the sol–gel process. Polyaniline (PANI) was prepared by the chemical-oxidative technique. An in situ approach was used for the synthesis of ACZ decorated PANI plastic nanocomposites (NCs). TEM, FTIR, FESEM, UV-visible, DSC, Raman, photoluminescence, and XRD techniques were used for characterizing the QDs, PANI, and ACZ decorated PANI NCs. Experimental and theoretical (DFT) studies were used to support the results. NCs were studied for their adsorption, magnetic, photocatalytic, electrical, thermal, photoluminescence, antibacterial, and anticorrosive activities. The plastic NCs of size 35 nm (observed from XRD and TEM) were found to be paramagnetic. UV-visible spectroscopy and DFT techniques were used to observe the optical band gap of NCs and show an almost equal band gap i.e., 2.75 eV. In 1.0 M H2SO4, the NCs show an 82.0% corrosion inhibition efficiency for mild steel. The adsorption power of the silica gel + NCs packed column was higher than normal silica gel column. A very small low-intensity D band in the Raman spectra confirms defect-free NCs. The photocatalytic activity was observed against methyl-red dye in visible light. The thermal stability of plastic NCs was higher than pure PANI and QDs. The NCs were investigated for bactericidal activity against Gram (positive and negative) microorganisms. The ACZ decorated PANI NCs acted as good nanomaterials for adsorption, separation, magnetic, photocatalytic, photoluminescence, antibacterial, electrical, thermal insulator, and anticorrosive agent.

ANTI-INFLAMMATORY ACTIVITY OF THE FOOD PLANT CALLIGONUM POLYGONOIDES L. FLAVONOIDS TARGETING NF-κB

Calligonum polygonoides L. subsp. comosum (Polygonaceae) is a wild shrub that grows on the sandy deserts of various regions in North Africa, Western Asia and Southern Europe. In some of Asian countries, the flower buds and young branches of the plant are used to prepare traditional food dishes. Also, different organs of C. polygonoides L. are used traditionally in treatment of stomach diseases. The isolation of anti-inflammatory lead compounds was performed by using different normal silica gel, reversed phase C-18, and sephadex LH-20 open columns. The identification of the isolated compounds was done using NMR spectral techniques. The isolated compounds are of different flavonoid classes; two flavonol glycosides; kaempferol-3-O-β-D-glucuronide and mequilianin, one flavan-3-ol; catechin, and one dihydro-flavonol; taxifolin. The methanol extract and ethyl acetate fraction of Calligonum polygonoides L. subsp. comosum exhibited anti-inflammatory activity against NF-κB translocation pathway on HEK293 cells. All of them were active against NF-κB translocation, and previously isolated from the plant under study. Kaempferol-3-O-β-D-glucuronide, a flavonoid glycoside demonstrated the most potent NF-κB inhibition in comparing with other flavonoids; taxifolin, catechin, and mequilianin. Therefore, the food plant aerial parts of C. polygonoides are rich in nutraceuticals (flavonoids and flavonoid glycosides) that can be utilized in the treatment of vascular inflammation.

4-Dimethylaminopyridine grafted on MCM-41 as an efficient and highly stable catalyst for the production of α-tocopherol acetate

N,N′-dimethyl-N-(4-pyridyl)-1,2-ethanediamine (DMPE) as a special N-alkylation precursor of 4-dimethylaminopyridine (DMAP) was grafted on the surface of γ-chloropropylated functionalized mesoporous silica MCM-41 to prepare immobilized DMAP. Characterization results of small angle X-ray diffraction, thermogravimetry and derivative thermogravimetry, Fourier transform infrared, scanning electron microscopy, energy-dispersive X-ray and transmission electron microscopy indicated that DMAP was successfully covalently bound to the surface of MCM-41. The highest loading of DMAP reached 0.9 mmol/g, which was 2.5 times higher than that of DMAP immobilized on the normal silica gel. The prepared immobilized DMAP as nucleophilic heterogeneous catalysts was successfully used for the acetylation reaction to produce α-tocopherol acetate. The highest yield reached 90.1% under the optimal condition which was summarized as follows: immobilized DMAP 100 mg, substrates mole ratio (acetic anhydride/α-tocopherol) 3:1, reaction temperature 50 ℃, stirring intensity 500 rpm, reaction in toluene for 12 h. The recyclability and stability of the DMAP grafted MCM-41 were excellent, as demonstrated by its use 20 times during batch operation without any loss of productivity.

A new HPTLC platformed luminescent biosensor system for facile screening of captan residue in fruits

This study presented a HPTLC platformed luminescent biosensor system for screening captan residue. First, the potential bio-effects of layers materials on the detectability of a luminescent bacteria Photobacterium phosphoreum (ATCC 11040) as the sensor cell were assessed. From comparison, it was noteworthy that the combination of sensor cells with normal silica gel layer exclusively gave outstanding detectability (<10 ng/zone). On this basis, HPTLC mediated separation and biosensing was further optimized. Then, the obtained graphic results were digitally quantified via software processing, offering satisfactory selectivity, linearity (R2 = 0.9901 within 10–80 ng/zone) and sensitivity (0.5 mg/kg against MRLs ≥ 6 mg/kg). Additionally, the performance of the established method was validated with different fruits (recover rates 75–96%, RSD < 11.8%). Meanwhile, it was demonstrated that detectability of this hybrid system would be tuneable by altering the combination of bacteria strains and layer materials, which was meaningful to strengthen the usability of microbial biosensors.

Fluorenyl Based Macrocyclic Polyradicaloids.

Synthesis of stable open-shell polyradicaloids including control of intramolecular spin-spin interactions is a challenging topic in organic chemistry and materials science. Herein, we report the synthesis and physical characterization of two series of fluorenyl based macrocyclic polyradicaloids. In one series (FR-MCn, n = 4-6), the fluorenyl radicals are directly linked at 3,6-positions; whereas in the other series (MC-FnAn, n = 3-5), an additional ethynylene moiety is inserted between the neighboring fluorenyl units. To access stable macrocyclic polyradicaloids, three synthetic methods were developed. All of these stable macrocycles can be purified by normal silica gel column chromatography under ambient conditions. In all cases, moderate polyradical characters were calculated by restricted active space spin-flip method due to the moderate intramolecular antiferromagnetic spin-spin interactions. The excitation energies from the low-spin ground state to the lowest high-spin excited state were evaluated by superconducting quantum interference device measurements. Their physical properties were also compared with the respective linear fluorenyl radical oligomers (FR-n, n = 3-6). It is found that the geometry, i.e., the distortional angle and spacer (w or w/o ethynylene) between the neighboring fluorenyl units, has significant effect on their polyradical character, excitation energy, one-photon absorption, two-photon absorption and electrochemical properties. In addition, the macrocyclic tetramers FR-MC4 and MC-F4A4 showed global antiaromatic character due to cyclic π-conjugation with 36 and 44 π-electrons, respectively.

Thin-layer chromatography of benzoic acids with a controlled gas phase: A comparison of different stationary phases

A comparison of the chromatographic behavior of benzoic acids on normal (silica gel), reversed (RP-18), and polyamide-11 plates using thin-layer chromatography (TLC) with controlled gas phase inside the chamber has been performed. This variant of TLC is based on the use of a gas phase moving over the TLC plate for regulation of the stationary and mobile phases as well as the acid—base properties of analytes during the separation process. The feasibility of such an approach is illustrated by the separation of benzoic acid derivatives using carbon dioxide, ammonia, and acetic acid vapor. It was shown that a gradual change of mobile phase acidity makes it possible to enhance separation efficiency and selectivity, this effect being dependent on the type of the stationary phase. The most considerable change in the retention of benzoic acid derivatives was observed for normal-phase plates with silica gel or silica sol, or starch binders used as the stationary phase. An alteration of surface acidity for polyamid...

Anti-inflammatory sesquiterpenes from Costus speciosus rhizomes

Ethnopharmacological relevanceCostus speciosus (Koen ex. Retz.) Sm. (crepe ginger, family Costaceae) is an ornamental plant used in traditional medicine for the treatment of inflammation, rheumatism, bronchitis, fever, headache, asthma, flatulence, constipation, helminthiasis, leprosy, skin diseases, hiccough, anemia, as well as burning sensation on urination. Aim of the studyThe present study is designed to isolate and identify the active compounds from C. speciosus rhizomes and measure their anti-inflammatory activities. Materials and methodsThe n-hexane–CHCl3 soluble fraction of the MeOH extract of C. speciosus rhizomes has been subjected to a repeated column chromatography, including normal silica gel and RP-18 column to give eight compounds. The structures of these compounds were established by UV, IR, 1D (1H and 13C), and 2D (1H–1H COSY, NOESY, HSQC, and HMBC) NMR experiments and HRESIMS data. In addition, the anti-inflammatory activity of compounds 1–8 was evaluated by measuring the levels IL-6, IL-1β, TNF-α, COX-2, lipoxgenase-5, and PGE2 using enzyme-linked immunosorbent assay. ResultsThe n-hexane–CHCl3 soluble fraction afforded a new eudesmane acid, specioic acid (8), along with seven known compounds, 22,23-dihydrospinasterone (1), dehydrodihydrocostus lactone (mokko lactone) (2), dehydrocostus lactone (3), stigmasterol (4), arbusculin A (5), santamarine (douglanin) (6), and reynosin (7). Compounds 1, 4, and 5–7 were isolated for the first time C. speciosus. Compounds 1–4 displayed potent anti-inflammatory activity, while 7 and 8 showed moderate activity. Compounds 1–8 exhibited a concentration-related decrease in the levels of IL-1β, IL-6, TNF-α, PGE2, lipoxgenase-5, and COX-2. Compounds 5 and 6 did not significantly decrease levels of different cytokines, PGE2, lipoxgenase-5, and COX-2 from PHA treatment at 1µM. However, all tested compounds significantly decreased cytokines, PGE2, lipoxgenase-5, and COX-2 levels at concentration 100µM. It is noteworthy that compounds 1–4 had the highest activity, where it lowered levels of cytokines, PGE2, lipoxgenase-5, and COX-2 to the extent that was no statistical difference from the control group. Thus, they decreased proinflammatory cytokines (IL-1β, IL-6, and TNF-α) with decreased level of the target enzymes (COX-2 and lipoxgenase-5) and subsequent reduction of its inflammatory product (PGE2). ConclusionGood anti-inflammatory activities exhibited of the isolated compounds from C. speciosus corroborate the usefulness of this plant in the traditional treatment of inflammation and related symptoms.

Three new ent-kaurane diterpenoids from Isodon rubescens and their cytotoxicities

AimTo study the chemical constitutions of the aerial parts of Isodon rubescens in Jianshi county, Hubei Province, China. MethodCompounds 1–9 were isolated and purified by normal silica gel and C18 reversed phase silica gel column chromatography, and HPLC. Their structures were elucidated by extensive spectroscopic methods (IR, UV, MS and NMR), and the absolute configuration of 1 was determined by single crystal X-ray diffraction. Compounds 1–9 were evaluated for their in vitro cytotoxicity against human tumor HL-60, SMMC-7721, A-549, MCF-7, and SW-480 cell lines. ResultEight ent-kaurane diterpenoids and one ent-gibberellanoid were isolated and identified. ConclusionCompounds 1–3 (jianshirubesins G-I) were new diterpenoids, of which 2 was a rare 3, 20-epoxy-ent-kaurane with a hemiketal at C-3. Among all of the diterpenoids tested, compounds 4 and 5 exhibited moderate inhibitory activity on the proliferation of certain cancer cells.

Hydrophobically Assisted Separation-Friendly Mitsunobu Reaction

A separation-friendly Mitsunobu reaction using hydrophobic-tagged acids is reported. Commercially available or simply prepared and recyclable hydrophobic-tagged acids can react with various alcohols to afford the target products in high yield with easy purification based on C-18 silica solid-phase extraction or normal silica gel filtration.

Normal silica gel and reversed phase thin-layer chromatography coupled with UV spectroscopy and IR-MALDI-o-TOF-MS for the detection of tetracycline antibiotics

Tetracyclines (TCs) form a group of bacteriostatic antibiotics with closely related structures and similar chemical and physicochemical properties. They are widely employed as therapeutics in human and veterinary medicine. Here, we introduce the combination of UV spectroscopic detection of high-performance thin-layer chromatography (HPTLC)-separated TCs with direct analysis on solid phase using infrared matrix-assisted laser desorption/ionization orthogonal time-of-flight mass spectrometry (IR-MALDI-o-TOF-MS). Normal silica gel phase- and water-wettable hybrid C(18) reversed phase layers (RP-18W) both allowed HPTLC separation and sensitive UV spectroscopic detection followed by MS analysis of distinct TCs bands using the liquid matrix glycerol. The novel approach of direct IR-MALDI-o-TOF-MS analysis resulted in the unequivocal identification of four structurally different TCs employed in this study, and linear calibration curves were produced for analyte amounts from 20 ng to 1 μg. MS analysis of TCs from RP-18W HPTLC plates was found to be superior when compared to the spectra acquired from the silica gel layer. Ionic analytes obtained from the RP-18W surface are mainly detected as protonated species of high abundance accompanied by a reduced formation of adducts as well as background ions arising from the matrix or the stationary phase. This results in decreased complexity of the spectra and enhanced sensitivity of the combinatorial method. An approximate detection limit of 5 ng of individual TCs in mixtures by combining RP-18W HPTLC with IR-MALDI-o-TOF-MS offers a novel timely and cost-efficient method for tracing TCs.

Improvement in the quality of used sunflower oil by organic and inorganic adsorbents

SummaryThe objective of the present work was to improve the quality of used sunflower oil. Inorganic (normal and modified silica gel) and organic (normal and modified cellulose powder) adsorbents were used as regeneration agents. Sunflower oil was heated at 180 ± 5 °C, 4 h every day for five consecutive days. The adsorbent materials were individually added to use sunflower oil at 2% level (w/v). Some physico‐chemical characteristics were measured to assess the quality of treated‐used sunflower oil. The results indicated that all adsorbents under study were effective in improving the overall quality of used sunflower oil. Normal silica gel with small particle size permitted high adsorbing capacity and close to that induced with Magnesol XL which is used commercially in a large scale to improve oil quality. The polarity of the adsorbent substance had a remarkable effect on removing the secondary oxidation products of used sunflower oil. The mode of adsorbents action is discussed.

Two new acylated triterpenoid saponins from Tetrapleura tetraptera

Tetrapleura tetraptera (Schum. et Thonn.) Taub. (Mimosaceae) is a tree that grows in the West and Central Africa. This plant has many pharmacological and ethnopharmacological potential uses, such as the treatment against convulsions, leprosy, inflamation, rheumatism [1,2], flatulence, jaundice, fevers [3], and epilepsy [4]. As part of our continuing search for new bioactive triterpene saponins from Cameroonian medicinal plants, a butanol fraction of the methanolic extract of the stem bark of T. tetraptera was submitted to multiple chromatographic steps (VLC, FLASH, MPLC on normal Silica gel and reversed phase Silica gel) affording two new acylated triterpenoid saponins (1) and (2). Their structures characterized as 3-O-{β-D-glucopyranosyl-(1→3)-6-O-[(2E,6S)-2,6-dimethyl-6-hydroxy-octa-2,7-dienoyl]-β-D-glucopyranosyl-(1→2)-β-D-glucopyranosyl-(1→4)]-[β-D-glucopyranosyl-(1→2)]-β-D-glucopyranosyl} 3,27-dihydroxyoleanolic acid (1) and 3-O-{β-D-glucopyranosyl-(1→2)-β-D-glucopyranosyl-(1→3)-β-D-glucopyranosyl(1→4)-[6-O-(E)-feruloyl]-β-D-glucopyranosyl-(1→4)-β-D-glucopyranosyl} 3,27-dihydroxyoleanolic acid (2), were mainly established by extensive analysis of 1D- (1H and 13C/DEPT) and 2D-NMR experiments (COSY, NOESY, TOCSY, HSQC, HMBC) and FAB- and HRESI-mass spectrometry.

Silicic Acid Polymerization Catalyzed by Amines and Polyamines

Abstract Amines, particularly polyamines, catalyzed the polycondensation of silicic acid in water. The resultant gel contained these polyamines with a N/Si molar ratio of up to 0.5. IR and powder X-ray studies showed that silica gel and polyamines are hybridized at a molecular level through hydrogen bonding. The gel adsorbed anionic dyes from water, whereas normal silica gel adsorbs cationic dyes. Induced CD was observed for the indigo carmine adsorbed on silica gel–poly(l-lysine) hybrid, showing that the hybrid provides a chiral environment to the adsorbate.

A New Type of Two-Dimensional Thin-Layer Chromatography (TLC Mapping) for Analysis of Acidic Glycosphingolipid Molecular Species

A new approach to the analysis of acidic glycosphingolipid molecular species has been developed by using two-dimensional thin-layer chromatography: TLC mapping. TLC mapping was accomplished by use of two types of high-performance thin-layer chromatographic (HPTLC) plates. A NH 2-silica gel HPTLC plate developed with chloroform:methanol: 1% diethylamine (50:47:15) was used for the first-dimension chromatography. Acidic glycosphingolipids on the plate were transferred to a normal silica gel HPTLC plate by developing the plate with chloroform:methanol:ammonia (4:10:6) after the NH 2 plate was placed face to face on top of the silica gel HPTLC plate. Acidic glycosphingolipids on the HPTLC plate were then developed with chloroform: methanol:0.2% CaCl 2 (60:40:10) for the second-dimension chromatography. The use of the TLC-mapping method allowed us to compare detailed membrane constituents, including minor molecular species with regard to acidic glycosphingolipids. The method is rapid and simple and is feasible for determining acidic glycosphingolipid from biological samples.

Microwave‐mediated methanolysis of lipids and activation of thin‐layer chromatographic plates

AbstractA technique is described for the methanolysis of fatty acids from acylglycerols with HCl/CH3OH or NaOH/CH3OH using a microwave oven. The esterification is rapid and complete and does not result in significant degradation of polyunsaturated fatty acids, even in the presence of oxygen. The fatty acid compositions of intact tissues were also determined using this technique. The microwave oven has also been used to condition normal silica gel and argentation thin‐layer chromatographic plates in a fraction of the time normally required.

The Selection of Noncorrelated Thin-Layer Chromatographic (TLC) Solvent Systems for the Comparison of Dyes Extracted from Transferred Fibers

Abstract The potential of using a combination of normal and reverse phase thin-layer chromatography for the comparison of disperse, acid, and reactive dyes extracted from textile fibers of forensic science origin was examined. For disperse and acid dyes, the use of a normal silica gel and a reverse phase system was shown to provide a pair of systems of low correlation. In contrast, the use of two silica gel systems provided a pair of highly correlated systems that possibly offered little more additional information than a single system. A suitable reverse phase system for the separation of reactive dyes was not found. The various pairs of silica gel systems tested for reactive dyes were all shown to be highly correlated.

Buffered Silicagel Systems - An Alternative Method for the Separation of Polar Compounds

Abstract The adsorption chromatography of polar compounds on normal silicagel gives very often strongly tailing peaks and, therefore, poor resolution. By coating the surface of the silicagel with a buffer salt, the tailing disappears and all the advantages of adsorption chromatography can be used. On buffered silicagel, nonionic compounds behave in the same way as on the untreated adsorbent. In this paper we describe the influence of type, pH and concentration of the buffer solution used to modify the silicagel on the performance of the separation system. The changes in separation selectivity and various applications are shown.