Biomedical subjects
Publications and source records attributed to Abdul Malik.
Hispidone, a new flavanone, has been isolated from Onosma hispida and assigned the structure (2S)-5,2'-dihydroxy-7,4',5'-trimethoxyflavanone (1) by spectroscopic methods. In addition, (2S)-5,2'-dihydroxy-7,5'-dimethoxyflavanone (2), benzoic acid (3), and 4-hydroxy benzoic acid (4) are also reported for the first time from this species.
Sol-gel capillary microextraction (sol-gel CME) is introduced as a viable solventless extraction technique for the preconcentration of trace analytes. To our knowledge, this is the first report on the use of sol-gel-coated capillaries in analytical microextraction. Sol-gel-coated capillaries were employed for the extraction and preconcentration of a wide variety of polar and nonpolar analytes. Two different types of sol-gel coatings were used for extraction: sol-gel poly(dimethylsiloxane) (PDMS) and sol-gel poly(ethylene glycol) (PEG). An in-house-assembled gravity-fed sample dispensing unit was used to perform the extraction. The analysis of the extracted analytes was performed by gas chromatography (GC). The extracted analytes were transferred to the GC column via thermal desorption. For this, the capillary with the extracted analytes was connected to the inlet end of the GC column using a two-way press-fit fused-silica connector housed inside the GC injection port. Desorption of the analytes from the extraction capillary was performed by rapid temperature programming (at 100 degrees C/min) of the GC injection port. The desorbed analytes were transported down the system by the helium flow and further focused at the inlet end of the GC column maintained at 30 degrees C. Sol-gel PDMS capillaries were used for the extraction of nonpolar and moderately polar compounds (polycyclic aromatic hydrocarbons, aldehydes, ketones), while sol-gel PEG capillaries were used for the extraction of polar compounds (alcohols, phenols, amines). The technique is characterized by excellent reproducibility. For both polar and nonpolar analytes, the run-to-run and capillary-to-capillary RSD values for GC peak areas remained under 6% and 4%, respectively. The technique also demonstrated excellent extraction sensitivity. Parts per quadrillion level detection limits were achieved by coupling sol-gel CME with GC-FID. The use of thicker sol-gel coatings and longer capillary segments of larger diameter (or capillaries with sol-gel monolithic beds) should lead to further enhancement of the extraction sensitivity.
The development of sol-gel open-tubular column technology in capillary electrochromatography (CEC) is reviewed. Sol-gel column technology offers a versatile means of creating organic-inorganic hybrid stationary phases. Sol-gel column technology provides a general approach to column fabrication for microseparation techniques including CEC, and is amenable to both open-tubular and monolithic columns. Direct chemical bonding of the stationary phase to the capillary inner walls provides enhanced thermal and solvent stability to sol-gel columns. Sol-gel stationary phases inherently possess higher surface area, and thus provide an effective one-step alternative to conventional open-tubular column technology. Sol-gel column technology is applicable to both silica-based and transition metal oxide-based hybrid stationary phases, and thus, provides a great opportunity to utilize advanced material properties of a wide range of nontraditional stationary phases to achieve enhanced selectivity in analytical microseparations. A wide variety of stationary phase ligands can be chemically immobilized on the capillary inner surface using a single-step sol-gel procedure. Sol-gel chemistry can be applied to design stationary phases with desired chromatographic characteristics, including the possibility of creating columns with either a positive or a negative charge on the stationary phase surface. This provides a new tool to control electroosmotic flow (EOF) in the column. Column efficiencies on the order of half a million theoretical plates per meter have been reported for sol-gel open-tubular CEC columns. The selectivity of sol-gel stationary phases can be easily fine-tuned by adjusting the composition of the coating sol solution. Open-tubular columns have significant advantages over their packed counterparts because of the simplicity in column making and hassle-free fritless operation. Open-tubular CEC columns possess low sample capacity and low detection sensitivity. Full utilization of the analytical potential of sol-gel open-tubular columns will require a concomitant development in the area of high-sensitivity detection technology.
Sphingolipid 1 and its corresponding beta-D-glucopyranoside derivative 2 have been isolated from the ethylacetate fraction of Conyza canadensis along with beta-sitosterol 3, stigmasterol 4, beta-sitosterol 3-O-beta-D-glucoside 5 and harmine 6, reported for the first time from this species. The structures of 1 and 2 were elucidated through spectroscopy including two-dimensional NMR.
Environmental pollution is one of the major problems being faced today due to the advent of extensive industrialization. Heavy metals are the most important contaminants in wastewater that are present in abundance and are toxic. Heavy metal contents of sewage in the industrial estate of Aligarh (U.P.) have been determined by atomic absorption spectrophotometry. The analysis of samples collected from six different locations revealed significantly high levels of Fe, Zn, Cu, Cr and Ni. Certain bacteriological (Total bacterial count, Total coliform. Fecal coliform, and Fecal Streptococci) parameters of domestic and industrial sewage as well as soils were monitored from March 1990 to January 1993. Total bacterial count, total coliform, fecal coliform and fecal streptococci were found to be lowest in all the samples of industrial wastewater compared to those in domestic sewage and soil systems. The soil however, contained highest total culturable bacterial population. In view of the common practice of the application of sewage to agricultural land in the neighbouring area, the discharge of industrial wastewater without proper treatment into public sewers should be strictly prohibited.
Pakistan is one of the few countries in Asia that continues to use only leaded-petrol as vehicular fuel. The concentration of Pb in its petrol reported in 1991 was the highest (1.5-2.0 g Pb L(-1)) of all produced by the various Asian countries and far exceeded the WHO's guideline of 0.15 g Pb L(-1). We have undertaken a study to trace and quantify this toxic element in the environs of Karachi. Pakistan's major metropolis, having more than 30% of the nation's total number of vehicles. In this article we report the Pb contents of petrol and diesel currently manufactured and marketed in the city. Samples of 'Regular' petrol collected in 1999 was found to contain 0.363 g Pb L(-1) (range: 0.335-0.390 g Pb L(-1)), a factor of 5 lower than that marketed prior to 1991. Its concentration in diesel fuel was much lower (0.017 g Pb L(-1)). Based on the available statistical data on the type and volume of vehicular traffic, we assessed that the current lead emission from vehicular traffic into the atmosphere is 391 metric tons a year, which is a factor of 2.7 lower than that estimated for 1989.
New triterpene, 3beta-(trans-cinnamoyloxy)-19alpha-hydroxy-urs-12-ene (1) has been isolated from the methanolic fraction of Debregeasia salicifolia, along with uvaol (2), 3beta,19alpha-dihydroxy-urs-12-ene (3), ursolic acid (4), pomolic acid (5), pomolic acid methyl ester (6) and tormentic acid (7) reported for the first time from this species. The compounds (1), (3) and (6) showed significant antimicrobial activity. The structure elucidation was made with the help of extensive 2D NMR spectroscopic techniques.
Two new oleanane triterpenes; 2alpha,3alpha,24-trihydroxyolean-12-ene-28,30-dioic acid ([structure: see text]) and 2alpha,3alpha,24,28-tetrahydroxyolean-12-ene ([structure: see text]) have been isolated from the roots of Atropa acuminata. Anti-oxidant p-hydroxyphenethyl trans-ferulate ([structure: see text]), beta-sitosterol-3-O-beta-D-glucopyranoside ([structure: see text]) and oleanolic acid ([structure: see text]) have also been reported for the first time from this species. The structures were determined by spectroscopic studies including 2D-NMR.
A new triterpene named as alysinol 3alpha, 22beta-dihydroxyolean-12-ene [structure: see text] along with known compounds usnic acid, methyl 2,4-dihydroxy-3,6-dimethyl benzoate, 3-hydroxy benzoic acid, stigmasterol, poriferasterol and ursolic acid have been isolated from Alysicarpus monolifer. The structure of [structure: see text] has been established through spectroscopic techniques.
Two new compounds, 7'-(3',4'-dihydroxyphenyl)-N-[(4-methoxyphenyl)ethyl]propenamide (4), and 7'-(4'-hydroxy,3'-methoxyphenyl)-N-[(4-butylphenyl)ethyl]propenamide (5) have been isolated from Cuscuta reflexa along with five known compounds, 6,7-dimethoxy-2H-1-benzopyran-2-one (1), 3-(3,4-dihydroxyphenyl)-2-propen-1-ethanoate (2), 6,7,8-trimethoxy-2H-1-benzopyran-2-one (3), 3-(4-O-beta-D-glucopyranoside-3,5-dimethoxyphenyl)-2-propen-1-ol (6), 2-(3-hydroxy-4-methoxyphenyl)-3,5-dihydroxy-7-O-beta-D-glucopyranoside-4H-1-benzopyrane-4-one (7), reported for the first time from this species. Structures of these compounds were determined by spectral analysis. These compounds showed strong inhibitory activity against alpha-glucosidase.
New sphingolipids, 1,3,5-trihydroxy-2-hexadecanoylamino-(6E,9E)-heptacosdiene (1). 1,3,5-trihydroxy-2-hexadecanoylamino-(6E,9E)-heptacosdiene-1-O-glucopyranoside (2). 1,3-dihydroxy-2-hexanoylamino-(4E)-heptadecene (3). have been isolated from Conyza canadensis, along with five known compounds, p-hydroxybenzoic acid, 3,5-dihydroxybenzoic acid, 3,5-dimethoxybenzoic acid, 3beta-hydroxyolean-12-en-28-oic acid, and 3beta-erythrodiol, isolated for the first time from this species. Their structures were determined by spectroscopic methods ((1)H- and (13)C-NMR, IR and MS) and two dimensional (2D)-NMR experiments.
Isoprenylated flavonoids 5,7-dihydroxy-3'-(2-hydroxy-3-methyl-3-butenyl)-3,6,4'-trimethoxyflavone (1), 3,7-dihydroxy-3'-(2-hydroxy-3-methyl-3-butenyl)-5,6,4'-trimethoxyflavone (2) and an isoprenylated acetophenone derivative (3) have been isolated from Duranta repens along with known compounds, 5-hydroxy-3,6,7,4'-tetramethoxyflavone (4), rosenonolactone (5), 6,7-dimethoxycoumarin (6), 5alpha,8alpha-epidioxyergosta-6,22-dien-3beta-ol (7) and 5alpha,8alpha-epidioxyergosta-6,9(11),22-trien-3beta-ol (8), isolated for the first time from this species. Their structures and the relative configuration were determined by spectroscopic methods (1H- and 13C-NMR, IR, UV and MS) and two-dimensional (2D)-NMR experiments. The compounds 1-5 showed inhibitory activity against prolyl endopeptidase while 4 and 5 were also active against thrombin.
A sol-gel method was used in preparing capillary gas chromatographic columns with simplicity and rapidity. Due to the formation of the chemical bonds between the coating layer and the inner wall of the capillary, the thermal stability of the column was greatly increased. The sol-gel poly(dimethyl-siloxane) (PDMS) column was able to withstand temperatures as high as 400 degrees C. This column showed excellent separation of free fatty acids, amines, and other polar compounds. The sol-gel column also showed good repeatability of retention time on a single column as well as good repeatability of capacity factor, column efficiency, symmetry and McReynold's constant on several columns of the same type.
The sample capacity is an important parameter of the gas chromatographic column. On a sol-gel-coated poly(dimethylsiloxane) (PDMS) capillary column and a conventional PDMS capillary column the probes undecane and fluoranthene were injected and the column efficiency was measured. After the injection amount was increased to a certain point, the column efficiency was reduced rapidly, and the amount that causes the efficiency reduction of ten percent is called the sample capacity of the column. The results show that the sample capacity of the sol-gel PDMS column is much higher than that of the conventional PDMS column. The reasons of higher sample capacity of a sol-gel column have been studied.
Copper(I) complexes of the type [CuX(PPh3)n(L)n]n {where X = Cl-, Br- I-, NO3, SCN-; PPh3 = triphenylphosphine and L = 4-ethylpyridine} have been prepared and characterized on the basis of their molecular weight, magnetic susceptibility, conductance, infrared studies and elemental analysis. Ethylpyridine behaved as monodentate ligand. The variation in stoichiometry and the probable structures of these complexes have been discussed.