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Biomedical subjects

Abdul Malik

Publications and source records attributed to Abdul Malik.

At least 19 recordsLinked to original sources
PubMed2007

Prevalence of hepatitis B virus genotype D in precore mutants among chronic liver disease patients from New Delhi, India.

Hepatitis B is one of the most important causes of chronic viral hepatitis world wide. Mutations in the precore region of the hepatitis B virus (HBV) genome are frequently found in hepatitis B envelope antigen-negative cases. Data from India on the HBV genotype-associated distribution of precore mutations are limited. Our objective in this study was to genotype and detect the precore mutant with a point mutation from G to A at nucleotide 1896 using ligase chain reaction (LCR) and direct sequencing. A total of 115 cases of chronic liver disease were screened. The cases were evaluated on the basis of history, clinical examination, liver function profile, and serological test for HBV infection, which includes HBsAg, anti HBcIgG, HBeAg using commercially available ELISA kits. The cases, which were HBeAg+, HBeAg-, and HBV DNA+, were subjected to LCR and confirmed by direct sequencing. Of 115 chronic liver disease cases, 50 (43.5%) cases were HBV DNA positive. All cases were subjected to LCR; 11 (22%) cases confirmed the presence of precore mutants, while the remaining 39 (78%) were classified as the wild form of the virus. HBV genotyping by direct sequencing revealed that genotype D was predominant in both wild and mutant forms of the virus. We conclude that the HBV genotype distribution was not significantly different between precore mutants and the wild form of the virus (P>0.05). North Indian patients with genotype D were more likely to have persistent HBV infection with precore mutants. HBV genotypes correlate with the clinical outcome of chronic HBV infection.

Adenine↗
PubMed2006

Biosorption of nickel and cadmium by metal resistant bacterial isolates from agricultural soil irrigated with industrial wastewater.

Agricultural soil irrigated with industrial wastewater (more than two decades) analysed for heavy metals revealed high levels of Fe, Cr, Cu, Zn, Ni and Cd. Out of a total of 40 bacterial isolates obtained from these soils, 17 belonged to the family enterobacteriaceae and 10 were Pseudomonas spp. A maximum MIC of 200 for Cd, 400 for Zn and Cu, 800 for Ni, and 1600 microg/ml for Pb was observed. Biosorption of Ni and Cd studies over a range of metal ion concentrations with Escherichia coli WS11 both in single and bi-metal systems showed that the adsorption of Cd and Ni was dependent on the concentrations and followed the Freundlich adsorption isotherm. The biosorption of Ni increased from 6.96 to 55.31 mg/g of cells, and Cd from 4.96 to 45.37 mg/g of cells at a concentration ranging from 50 to 400 microg/ml after 2h of incubation in a single metal solution. A further increase in incubation time had no significant effect on the biosorption of metals.

Adsorption↗
PubMed2006

Sol-gel immobilized cyano-polydimethylsiloxane coating for capillary microextraction of aqueous trace analytes ranging from polycyclic aromatic hydrocarbons to free fatty acids.

Sol-gel coating containing highly polar cyanopropyl and nonpolar poly(dimethylsiloxane) components (sol-gel CN-PDMS coating) was developed for capillary microextraction (CME). The sol-gel chemistry provided an efficient means to immobilize the CN-PDMS coating by establishing chemical anchorage between the coating and the fused silica capillary inner surface. This chemical bond provided excellent thermal and solvent stability to the created sol-gel coating. For the extraction of polar and nonpolar analytes, the upper allowable conditioning temperatures were 330 degrees C and 350 degrees C, respectively. To our knowledge, this is the first time when a CN-PDMS thick coating survived such a high operation temperature. The prepared sol-gel CN-PDMS coating provided effective extraction of polar and nonpolar analytes simultaneously from aqueous samples. The cyanopropyl moiety in sol-gel CN-PDMS coatings provided effective extraction of highly polar analytes such as free fatty acids, alcohols, and phenols without requiring derivatization, pH adjustment or salting out procedures. The PDMS moiety, on the other hand, provided efficient extraction of nonpolar analytes. The extraction properties of the sol-gel CN-PDMS coatings can be fine tuned via manipulation of relative proportions of 3-cyanopropyltriethoxysilane and hydroxy-terminated PDMS in the sol solution used to create the coatings. Detection limits of nanogram/liter (ng/L) were achieved for both highly polar and nonpolar analytes directly extracted from aqueous media using sol-gel CN-PDMS coated microextraction capillaries followed by GC analysis.

Chromatography, Gas↗
PubMed2006

Cucurbitacin glucosides from Citrullus colocynthis.

A new cucurbitacin glucoside 2-O-beta-D-glucopyranosyl-16alpha-20R-dihydroxy-cucurbita-1,5,23E,25(26)-tetraen-3,11,22-trione (1) has been isolated from the methanolic extract of the fruits of Citrulluscolocynthis. The structure has been assigned on the basis of spectral analysis including 1D and 2D NMR techniques. In addition 2-O-beta-D-glucopyranosyl-cucurbitacin B (arvenin I) (2) and 2,25-di-O-beta-D-glucopyranosyl-cucurbitacin L (3) are reported for the first time from this species.

Citrullus↗
PubMed2006

Synthesis and antibacterial activity of substituted flavones, 4-thioflavones and 4-iminoflavones.

Synthesis of flavones, 4-thioflavones and 4-iminoflavones was carried out with the substitution of variable halogens, methyl, methoxy and nitro groups in the A, B and AB rings of the respective compounds and we also report here their antibacterial activity. Most of the synthesized compounds were found to be active against Escherichia coli, Bacillus subtilis, Shigella flexnari, Salmonella aureus, Salmonella typhi and Pseudomonas aeruginosa. Activity of 4-thioflavones and 4-iminoflavones was found to be higher than that of their corresponding flavone analogues. Investigated compounds having substituents like F, OMe and NO2 at 4'-position in ring-B exhibited enhanced activity and the presence of electronegative groups in the studied compounds showed a direct relationship to the antibacterial activity.

Anti-Bacterial Agents↗
PubMed2006

Structure determination of ursene-type triterpenes by NMR techniques.

Two new ursene-type triterpenes, nudicauline A and nudicauline B, have been isolated from Launaea nudicaulis. Their structures have been assigned as 3beta-hydroxy-urs-11-ene (1) and 3beta-acetyl-urs-11-ene (2), respectively, by extensive NMR studies. In addition, olean-11,13(18)-diene (3), 3beta-hydroxy-13(28)-epoxy-urs-11-ene (4) and 3-keto-13(28)-epoxy-urs-11-ene (5) are also reported for the first time from this species.

Asteraceae↗
PubMed2006

Antioxidant activity with flavonoidal constituents from Aerva persica.

A new flavanone Persinol (1) and the new flavanone glucosides persinosides A (2) and B (3), along with known flavonoids (4 and 5) have been isolated from the ethyl acetate soluble fraction of the whole plants of Aerva persica. Their structures were elucidated on the basis of extensive analysis of nuclear magnetic resonance (1D and 2D-NMR) spectral data. All of them showed profound antioxidative activities by DPPH and cytochrome-c-reduction assays using the HL-60 cell culture system.

Amaranthaceae↗
PubMed2006

New butyrylcholinesterase inhibitory triterpenes from Salvia santolinifolia.

Slavins A (1) and B (2), the new amyrin type triterpenes, have been isolated from the chloroform soluble fraction of Salvia santolinifolia and assigned structures on the basis of spectral studies including 2D NMR. Both the compounds displayed inhibitory potential against the enzyme butyrylcholinesterase.

Butyrylcholinesterase↗
PubMed2006

New natural urease inhibitors from Ranunculus repens.

Phytochemical investigations on the chloroform and ethyl acetate soluble fractions of the roots of Ranunculus repens led to the isolation of methyl 3,4,5-trihydroxybenzoate 1, R(+)- 4-methoxydalbergione 2 and R(+)-dalbergiophenol 3. The structures of these compounds were established through spectral studies including 1D and 2D NMR experiments and by comparison with literature data. These compounds showed potent inhibitory activity against urease.

Benzoates↗
PubMed2006

Novel urease inhibitors from Daphne oleoids.

Phytochemical investigations on the chloroform and ethyl acetate soluble fractions of the roots of the Daphne oleoids led to the isolation of the coumarin glycosides 1-6. Compound 5 with IC50 values 22.05 and 26.30 microM repectively, was found to be the most active of these compounds when screened against Bacillus pasteurii and jack bean urease enzymes in a concentration-dependent fashion.

Daphne↗
PubMed2006

Xanthine oxidase inhibiting flavonol glycoside from Amberboa ramosa.

A new flavonol glycoside (1) has been isolated from the ethyl acetate soluble fraction of Amberboa ramosa and assigned the structure 5,7,4'-trihydroxy-3,8-dimethoxylflavone 5-O-beta-D-gluco-pyranoside (1). In addition, 6,4'-dihydroxy-3,5,7-trimethoxyflavone (2), 5,7-dihydroxy-4'-methoxyflavone (3) and (23R)-5alpha-cycloart-24-ene-3beta,21,23-triol (4) have also been reported for the first time from this species. The structures were deduced on the basis of 1D and 2D NMR techniques. The compounds 1-3 displayed weak to moderate inhibition against the xanthine oxidase enzyme.

Asteraceae↗
PubMed2006

Phenolic constituents from Perovskia atriplicifolia.

Perovskoate, an isorinic acid derivative (1) and perovskoside, the catechol derivative (2) have been isolated from the ethyl acetate soluble fraction of the whole plant of Perovskia atriplicifolia and assigned the structure 3(7-hydroxyphenyl)-2-hydroxy propanoic acid; (R)-form, 2-O-(6',7'-dihydroxy-E-cinnamoyl) (1) and 2-methoxy-4-(undecyl-4'-O-beta-D-glucopyranosyl) phenol (2). In addition, caffeic acid (3) and ferulic acid (4) have been reported for the first time from this species. The structures of these compounds were assigned on the basis of 1D and 2D NMR techniques. The compound 1 showed significant inhibitory activity against lipoxygenase and weak to moderate activity against cholinesterases.

Caffeic Acids↗
PubMed2006

Chymotrypsin inhibitory triterpenoids from Silybum marianum.

Marianine, the new lanostane triterpene (1) and marianosides A (2) and B (3) have been isolated from the whole plant of Silybum marianum. Their structures were elucidated on the basis of extensive analysis of their one dimensional and two dimensional nuclear magnetic resonance (1D, 2D-NMR) spectral data. All inhibited chymotrypsin in a concentration-dependent manner.

Asteraceae↗
PubMed2005

Isolation and cholinesterase-inhibition studies of sterols from Haloxylon recurvum.

Haloxysterols A-D (1-4), new C-24 alkylated sterols, have been isolated from the chloroform soluble fraction of Haloxylon recurvum, along with five known sterols 5-9, which are reported for the first time from this species. Their structures were determined by means of 1D- and 2D-NMR techniques. Compounds 1-9 inhibited cholinesterase enzymes in a concentration-dependent manner with K(i) values ranging between 0.85-25.5 and 1.0-19.0 microM against acetylcholinesterase (AChE; EC 3.1.1.7) and butyrylcholinesterase (BChE; EC 3.1.1.8) enzymes, respectively. Lineweaver-Burk, Dixon plots and their secondary replots indicated that compounds 1-9 are non-competitive inhibitors of both AChE and BChE enzymes.

Acetylcholinesterase↗
PubMed2005

Withanolides, a new class of natural cholinesterase inhibitors with calcium antagonistic properties.

The withanolides 1-3 and 4-5 isolated from Ajuga bracteosa and Withania somnifera, respectively, inhibited acetylcholinesterase (AChE, EC 3.1.1.7) and butyrylcholinesterase (BChE, EC 3.1.1.8) enzymes in a concentration-dependent fashion with IC50 values ranging between 20.5 and 49,2 microm and 29.0 and 85.2 microm for AChE and BChE, respectively. Lineweaver-Burk as well as Dixon plots and their secondary replots indicated that compounds 1, 3, and 5 are the linear mixed-type inhibitors of AChE, while 2 and 4 are non-competitive inhibitors of AChE with K(i) values ranging between 20.0 and 45.0 microm. All compounds were found to be non-competitive inhibitors of BChE with K(i) values ranging between 27.7 and 90.6 microm. Molecular docking study revealed that all the ligands are completely buried inside the aromatic gorge of AChE, while compounds 1, 3, and 5 extend up to the catalytic triad. A comparison of the docking results showed that all ligands generally adopt the same binding mode and lie parallel to the surface of the gorge. The superposition of the docked structures demonstrated that the non-flexible skeleton of the ligands always penetrates the aromatic gorge through the six-membered ring A, allowing their simultaneous interaction with more than one subsite of the active center. The affinity of ligands with AChE was found to be the cumulative effects of number of hydrophobic contacts and hydrogen bonding. Furthermore, all compounds also displayed dose-dependent (0.005-1.0 mg/mL) spasmolytic and Ca2+ antagonistic potentials in isolated rabbit jejunum preparations, compound 4 being the most active with an ED50 value of 0.09 +/- 0.001 mg/mL and 0.22 +/- 0.01 microg/mL on spontaneous and K+ -induced contractions, respectively. The cholinesterase inhibitory potential along with calcium antagonistic ability and safe profile in human neutrophil viability assay could make compounds 1-5 possible drug candidates for further study to treat Alzheimer's disease and associated problems.

Acetylcholinesterase↗