Medicinal Chemistry

It is likely that all proteins are modified post-translationally, either enzymatically or non-enzymatically. Scientists have continued to develop suitable methodologies in order to study the ever burgeoning list of protein post-translational modifications (PTMs). For the study of PTMs, one must consider suitable assays by which the target protein can be detected, the site(s) of PTM determined, the stoichiometry and stability of the PTM evaluated, and the biological outcome of the modification assessed. Historically, one of the methods of choice for identifying which protein is modified, and the site and stoichiometry of modification, has been the utilisation of commercial radiochemicals. Of these, tritium (3H) has excellent potential to facilitate analyses of biochemical reactions, but has the weakest signal strength of the commonly employed biological β-emitters. Hence development of imaging devices that are superior to conventional film autoradiography will enable a better exploitation of the universal application of 3H for measuring PTMs. Herein, we discuss the current application of film autoradiography and the advantages of using microchannel plate (MCP) autoradiographic imagers.

A large number of novel O -allylchalcones were synthesized by Claisen Schmidt condensation reaction of O -allylvanillin 3 with appropriate substituted acetophenones 4a-h. These model chalcones 5a-h and their precursor O -allylvanillin were screened for their in vitro cytotoxicactivity against four human cancer cell lines. The most potent compound in this series with the IC 50 values below or around 10 μM were 5f against THP-1 cells (10.42 μM) and 5g against THP-1 (4.76 μM), DU-145 (5.21 μM), HL60 (7.90 μM), Hep-G2 (10.12 μM) and MCF-7 (10.32 μM).

Aberrant post-translational modifications (PTMs) of proteins and the resultant disturbances of cellular signaling pathways typify many disease states. Hence the detection, localisation, and quantitation of PTMs represent important elements of disease analysis. Herein, chromatographic and electrophoretic methodology that may be exploited to first detect the protein(s) that is post-translationally modified, determine the site(s) of the PTM, quantify the stoichiometry of the modification, and then evaluate its stability is discussed. For proteins at which multiple PTMs occur, synthetic peptides that only encompass selected modification site(s) are useful for restricting analysis to specific PTMs. Suggestions for rational peptide design for studying discrete PTMs are detailed. Finally, intrinsic to these analyses of PTMs is the requirement of an evaluation of the functional outcome of the PTM.

In the present study, simple and fast spectrophotometricmethod have been reported for the determination of three macrolides i.e., erythromycin, roxithromycin and clarithromycin through charge transfer complexes. The method involves the interaction of macrolides with chloranilic acid in acetonitrile medium. Stoichiometry was found to be 1:1 for all the complexes. Under the optimizedconditions, the complexes were found to be absorbed at 498, 496 and 491 nm with in the linearity range of 3-36, 4-40 and 8-40 μg mL -1 with minimum detection limit 190, 600 and 370 ng mL -1 for respectively. The corresponding molar absorptivity values were determined to be 2.07×10 4 , 1.81×10 4 and 1.67×10 4 Mol -1 cm -1 respectively. The data is discussed in terms of oscillator’s strength, dipole moment, ionization potential, energy of complexes, resonance energy, association constant and Gibb’s free energy changes. Benesi- Hildebrand plots for all complexes have been constructed. Furthermore, the methods were successfully applied for the determination of studied macrolides in pharmaceutical formulations. The interday and intraday precision and percent recovery values were evaluated. Results of analysis were validated successfully. Commonly present excipients did not show interference during analysis

Oncidium flexuosum Sims. is an orchidwhose leaves are frequently used for therapeutic applications although its action mechanism is not exactly understood. So the aim of this study was investigate its effects in Wistar rat liver, kidney and bone marrow. For this purpose, twenty-five adult male Wistar rats were divided into five groups of 5 animals each: a control group receiving only water, a positive control receiving a mutagen compound and three groups treated for 15 days with 100, 250 or 500 mg/kg/day of a crude hydroalcoholic leaf extract of O. flexusosum Sims. No significant alterations were observed in –SH groups, MDA or catalase, showing that the extract does not induce hepatic oxidative damage. There was no evidence of kidney injury and hepatic function alteration (ALT). However, significant mitochondrial swelling was observed in the treated groups and is probably related to cell death induction observed in cells that displayed acidophilia, pyknosis and positive labeling with the TUNEL technique at higher concentrations of the extract. We demonstrated that the hepatotoxicity of the extract resulted from its ability to induce DNA and mitochondrial damage that arrests cells, leading to cell death, probably caused by the flavonoidsand tannins present in this extract.

The reaction of 2-bromo-3,4,5-trimethoxybenzaldehyde 1 with Pd(dba) 2 ; dba=dibenzylideneacetone) in the presence of a stoichiometric amount of nitrogen donor ligands, such as N,N,N’,N’ -tetramethyl-ethane-1,2-diamine (TMEDA), 2,2’-bipyridine (bpy) 4,4’-dimethyl-2,2’-bipyridine (dmbpy) and an 1,10-phenanthroline (Phen), should be added to with equimolar ratio in degassed acetoneunder nitrogen to give mononuclear σ-aryl palladium (II) complexes cis-[2- Pd{C 6 H(CHO)-6-(OMe) 3 -3,4,5}BrL 2 ] 3a-d, where L 2 =TMEDA (3a); L 2 =bpy (3b); L 2 =dmbpy (3c); L 2 =Phen (3d) in good yields 48-65%. The reaction of the synthesized five-membered C,N -palladacycle cis-[2-Pd{C 6 H(CHO)-6-(OMe) 3 -3,4,5} BrL 2 ] 3a-d, where L 2 =TMEDA (3a); L=bpy (3b); L 2 =dmbpy (3c); L 2 =Phen (3d), with an1-naphthylisocyanates (C 10 H 7 - NCO) and an 1-naphthylisothiocyanates (C 10 H 7 -NCS), leads to the formation of novel palladacycle 4a-d and 5a-d, which was characterized in solution by 1 H NMR spectroscopy. The solid products were characterized by satisfactory elemental analysis and spectra studies. All the resulting complexes 3a-d, 4a-d and 5a-d were tested in vitro against a number of cell lines. For example, it inhibited K562 leukaemia cells with an IC 50 value in the range of (3.00 -4.3) μM (1 h exposure) and displayed cathepsin B inhibitory action with an IC 50 value in the range of (0.045-0.055 μM)

An efficient analytical method for the simultaneous determination of leflunomideand non steroidal anti-inflammatory drugs in API and formulations by LC-UV has been developed. The analytes were separated on Purospher Star, C18 (5 μm, 250×4.6 mm) column at ambient temperature with methanol: water (80:20, v/v, pH at 2.7) at flow rate of 1.5 mL min-1. Experiment was conducted in two phases. Leflunomide was separated with flurbiprofenand ibuprofen (phase- I) and diclofenac sodium and mefenamic acid (phase II). Calibration curves were linear over the range 0.625–5 μg mL-1 in both phases for leflunomide while for flurbiprofen, ibuprofen, diclofenac sodium, mefenamic acid linearity were achieved in the range of 0.625-5, 11.25-90, 1.56-50 and 0.78-25 μg mL-1, respectively with r2>0.9998. Intraday variation was <1.2 and <1.4 %, while in inter-day ranged between 0.042-1.45% and 0.08-1.27% in phase-I and II, respectively. Mean recovery values for intra-day ranged from 99.04-100.4% and 98.48-100.2% and for inter-day were between 98.54-100.29% and 98.85-100.54% in phase-I and II, respectively. The LLOD of leflunomide was 13 ng mL-1, while LLOQ was 39ng mL-1, respectively. LLOD and LLOQ for flurbiprofen, ibuprofen, diclofenac sodium and mefenamic acid were 6.9, 296, 71 and 1.2 ng mL-1 and 21, 897, 214.3 and 3.676 ng mL-1, respectively. Present study showed that nanogram quantities of all the compounds can be estimated accurately. The newly established method was successfully applied to study in vitro interactions between leflunomide and NSAIDs.