Current Advances in Chemistry and Biochemistry Vol. 9

This paper introduces an organic solvent-free mobile phase HPLC system for simultaneous analysis of tetracycline (TC) and 4-epi-tetracycline (4eTC). The chromatographic separation was achieved an Inertsil\(&#x24C7;\) WP300 C4 column with an isocratic aqueous mobile phase and a photodiode array detector (PAD). The run-time was < 5 min/sample. The main validation performance parameters, linearity, range, and system suitability, were well within the international recommended criteria. The detection limits for TC and 4eTC were 0.005 and 0.014 \(\mu\)g/mL, respectively. The high repeatable, quick, and easy HPLC-PAD system may be further effective for the quantifying TC and 4eTC residues in animal-derived foods.

Methylation of a hydroxy group annihilate or at least decrease the capacity of that group to form hydrogen bonds. The effect is still more pronounced by the reduction of a hydroxy group to a methylene (deoxy) one. The major methyl donor in the cells of living organisms is S-adenosyl-methionine (Ado-Met). Sometimes, methyl group is donated by N⁵,N¹⁰-THFA or from a cobalt atom of a corrin ring. In spite of the relatively low variety of natural methyl donors (compare with phosphate donors), partially reduced or methylated sugars have been found in glycosterols, polysaccharides, glycosphingolipids, gangliosides, antigenic phenolic glycolipids, inositols, nucleoside-type glycosides. Methylation of nucleic acids is made especially on cytosine and adenine, and of protein on Glu and Asp.

Four different prepared extracts from roselle (Hibiscus sabdariffa Linn.) calyxes were stored differently with chemical preservatives (sodium benzoate, sodium metabisulphite, boric acid, and citric acid) for eight weeks. A control, sample without preservative was also stored for the same period. They were understudied weekly for changes in the pH, ascorbic acid content, and microbial population. The research was carried out to studying the influence of the chemical preservatives on the pH, vitamin C, and microbial population of the extract during storage. Up to the first three weeks of storage, the vitamin C contents of the entire juices were not statistically different (p = 0.05) except, sample preserved with sodium benzoate. In the same manner, with exception of samples stored without preservative and with sodium metabisulphite, other samples were not significantly different (p = 0.05) with respect to pH. With exception of the control, spoilage started between third and sixth week of storage while sodium metabisulphite inhibited the growth of microbes till the end of the studied week. Generally, the results from this study revealed a decrease in pH (increase in acidity), a reduction in ascorbic acid content and an increase in microbial population as the storage time was extended in the entire samples but more explicit in the sample stored without preservative. The rate of change of pH and percentage reduction in ascorbic acid with respect to storage time in the sample without preservative increased tremendously compared to other juices stored with preservatives. This study showed that the chemical preservatives prohibited rapid loss of vitamin C and inhibited the growth of microorganisms that might have caused spoilage of this juice during storage. The use of chemical preservatives to prolong the shelf-life of this juice is therefore advocated so as to make it more available round the year.

Recently, some researchers have investigated the recovery of gold using microbial cells, such as bacteria, fungi, yeasts, and algae. However, there is little information on which kind of microorganisms has a high gold adsorbing ability. We have reported various species and strains of bacteria, actinomycetes, fungi, and yeasts were screened for their ability to adsorb gold from a solution containing hydrogen tetrachloroaurate (III). Hydrogen tetrachloroaurate (III) is used for medical and ceramic materials. The effect of pH, external gold concentration, cell amounts on gold biosorption, and the time course of gold biosorption by Pseudomonas maltophilia cells, which adsorbed large amounts of gold from a solution containing hydrogen tetrachloroaurate (III), were reported in detail. In this chapter, in order to approve the amount of gold recovery much higher, the removal of gold (III) by biosorption and biomineralization from aqueous systems using microbial cells, gold (III) removal by those using microbial cells was investigated. Additionally, the oxidative recovery of gold after reduced gold(0) by the oxidation using aqueous thiourea solution, and recycles of gold reduction-oxidation cycles.

Imidazole-2-carboxaldehyde was condensed with 2-amino-3-carboxyethyl-4,5-dimethyl thiophene in 1:1 molar ratio yielded Schiff base. Co^II, Ni^II, Cu^II and Zn^II complexes of Schiff base were synthesized and characterized. The geometry exhibited by the complexes was proposed using magnetic and electronic spectral data. Thermal analysis was carried out to ascertain the thermal stability of the compounds. The fluorescence spectral analysis were investigated at different solvents for the Schiff base and its Cu^II complex. Using powder XRD measurements, the grain size was determined. The SEM images indicate the surface morphology of the complexes. The antibacterial and antifungal activities were screened by disk diffusion method designed by Kirby-Bauer. In vitro anticancer studies were carried out, by MTT assay for human cervical carcinoma cell line.

The thermal decomposition process developed in the present work is a viable technique for the formation of a nano (TiO₂-SiO₂) composite coating on Titanium substrate. The electrochemical experiments revealed that the developed coatings had high degradation resistance characteristics and high biomimetic growth characteristics. There was no degradation on the coating even when it was subjected to different extent of electrochemical polarization and anodic current impression. The biomimetic growth studies of these coatings were carried out. The results of elemental analysis of the SBF solution, electrochemical characterization and surface topographical analysis including SEM and AFM carried out at different stages revealed that there was an efficient apatite growth.

Vegetable oils from the Amazon can serve as raw materials for the cosmetics, pharmaceuticals, and human and animal food industries. The region has always offered raw material in natura and with no added value. Therefore, it is strategic to develop (bio) technological processing of these inputs and commercialize them with high added value The synthesis and production on an industrial scale of molecules of very high added value, such as lipases, dyes, functional foods and cosmetics can promote a rational use of Amazonian biodiversity as a source of “fine chemicals”, consolidating a modern bioindustry in the region.

The simultaneous measurement of trenbolone acetate and 17\(\beta\)-trenbolone in cattle muscle is described using an affordable, safe, and rapid sample preparation procedure followed by reversed-phase high-performance liquid chromatography (HPLC). HPLC analysis with a photo-diode array detector was carried out on a short C1 column with an isocratic mobile phase. The method was validated through analyses of spiked samples, resulting recoveries (\(\ge\) 87.9%; relative standard deviations \(\le\) 3.4%), analytical total time (< 20 min/sample, where, a batch of 12 samples was completed in 2 hours), and quantitation limits (\(\le\) 1.8 ng/g). The proposed technique for determination of TBa and \(\beta\)-TB in beef (cattle muscle) is a useful tool for the routine residue monitoring in beef and the withdrawal control of beef farm. No harmful organic solvents and reagents were used at all.

The rate and the extent of drug dissolution and its absorption depend on the characteristics of the active pharmaceutical ingredient (API) as well as the dosage form properties. In this work dissolution profiles of furosemide tablets of nine commercial products marketed in Argentine were evaluated. All Brands fulfill the specifications of dissolution test of USP. Comparison of dissolution profiles were carried out by model-dependent and model independent approaches. The Weibull model provided the best kinetic curve adjustment. Brands IV, VI and IX had the best fitting, with the maximum determination coefficient and the smallest AIC values. Results obtained via model-independent approach show that there was not significative difference in Dissolution efficiency between the reference product and Brands II, III and IV and in Mean dissolution time between the reference product and Brands II, III, IV and V. Using fit factors, only Brands I and III were similar. It has been demonstrated in vivo bioequivalence of furosemide market products interchangeability with generics should be avoided.

Automatic prediction of bi-molecular protein complexes and biomolecular interactions has been the object of a diversity of computational studies and with different degrees of success. Extrapolating these methodologies to treat the harder problem of computing the structure and function of multi-meric proteins, however, poses several complications. The most relevant stems from the combinatorial aspect of the problem, which involves the prediction of the dynamic order in which the subunits interact (the interaction path). A second, not less important, is the size of these molecules which account for thousands of atoms, and thus require sophisticated computational platforms.

In this chapter we entail the efforts of a recent study oriented to the automatic elucidation of protein multimeric configurations and thereby the dynamic order of multimeric protein complex formation. The study is namely based on the development of a genuine approach that requires as unique information that of the isolated structures of each of the subunits constituting the multimeric complex. The method is based on an original protocol we have implemented to infer interaction sites on protein surfaces. Hitherto attempts to solve this relevant problem in protein function elucidation have been limited to three body dockings using conventional docking algorithms and molecular dynamic simulations. Here the aim is to infer complex configurations and dynamic orders of formation from the monomers known to constitute a multimeric complex unveiling active regions on the surfaces of the proteins and intermediate complexes. We present three case studies and show that important insights into the formation mechanisms of this type of multimeric complexes can be gained from the analysis of the surface characteristics of the interacting monomers which can facilitate, in a further stage, the docking and energy calculations involved in the prediction of the configurations of these complexes.

Parkinson’s disease (PD) is a neurodegenerative disorder characterized by the progressive    loss of dopaminergic neurons mainly in the substantia nigra. The L-3,4-dihydroxyphenylalanine (LD) is the gold standard drug currently used to manage Parkinson’s disease (PD) and to control its symptoms. However, LD could cause disease neurotoxicity due to the generation of pro-oxidant intermediates deriving from its autoxidation. In order to overcome this limitation, we have conjugated LD to the natural antioxidant glutathione (GSH) to form a codrug (GSH-LD). Here we investigated the effect of GSH-LD on H₂O₂-induced cellular toxicity in undifferentiated and differentiated lymphoma U-937 and dopaminergic neuroblastoma SH-SY5Y cell lines, used respectively as models to study the involvement of macrophages/microglia and dopaminergic neurons in PD. We analyzed the effect of GSH-LD on apoptosis and cellular oxidative stress, both considered strategic targets for the prevention and treatment of neurodegenerative diseases. Compared to LD and GSH, GSH-LD had a stronger effect in preventing hydrogen peroxide (H₂O₂) induced apoptosis in both cell lines. Moreover, GSH-LD was able to preserve cell viability, cellular redox status, gluthation metabolism and prevent reactive oxygen species (ROS) formation, in a phosphinositide 3-kinase (PI3K)/kinase B (Akt)-dependent manner, in a neurotoxicity cellular model. Our findings indicate that the GSH-LD codrug offers advantages deriving from the additive effect of LD and GSH and it could represent a promising candidate for PD treatment. The significance of our observations need to be validated in further studies investigating the neuroprotective effects of GSH-LD in PD in in vivo animal models and its ability to penetrate effectively the BBB.

Fabrication of hybrid hydrogels to improve biological properties or to decrease the disadvantages of biomaterials has been a popular approach. With the background of snowballing threat of skin wound to public health and economy, this study was undertaken utilizing xanthan gum (Xnt), citric acid (C), gelatin (Gel), glutaraldehyde (G) and HPLC-grade water to fabricate a series of composite hydrogels i.e. Xnt, Xnt:C, Xnt:Gel(3):G, Xnt:C:Gel(3):G, Xnt:Gel(5):G, Xnt:C:Gel(5):G for investigating their wound healing efficacy in experimental rat skin wound model. Physicochemical characterization revealed that all the composite hydrogels contained more than 90% water. The hydrogels displayed swelling ability, biodegradability, good polymeric networks and porosity. Fourier Transform Infrared Spectroscopy (FT-IR) studies confirmed the presence of bound water and free, intra and inter molecular bound hydrogen bonded OH and NH in the hydrogels. All the hydrogels showed significant wound healing potency in experimental deep second degree skin burns in rats compared to controls. 20 days post-application of hydrogels, Xnt:Gel(3):G, Xnt:Gel(5):G and Xnt:C:Gel(5):G-treated wounds showed better recovery compared to other composite hydrogels. The highest wound contraction of these hydrogel composites might be due to presence of Gel in the formulations.  We conclude that, Xnt:Gel(3):G, Xnt:Gel(5):G and Xnt:C:Gel(5):G might be effective wound dressing material.