SYNTHESIS OF NOVEL TETRAHYDROTHIAZOLO(5,4-c)PYRIDINES AND IN- VITRO EVALUATION OF THEIR ANTI-INFLAMMATORY ACTIVITY

Abstract

The discovery of new anti-inflammatory drugs with novel mechanisms is an ongoing effort and process by medicinal chemists to combat inflammatory disorders. These disorders consist of rheumatoid arthritis, anaphylaxis, tuberculosis, cancer, asthma, ulcerative colitis etc. The medicinal chemists always try to discover and explore new template molecules as effective treatment options for the inflammatory disorders. Tetrahydrothiazolo[5,4-c]pyridine (THTP) is a fused bicyclic template with limited compounds reported in the literature which are being evaluated for a few disorders such as Parkinson’s disease, venous thromboembolism, obesity, gastritis, tuberculosis and microbial infections. Therefore, in this MSc research project, I designed and synthesised seven novel compounds consisting of THTP core moiety. The multi-step synthesis was initiated with an intermediate enamine formation followed by derivatisation using reagents such as carboxylic acid, acyl chloride, sulfonyl chloride and isocyanate to yield final compounds. All the compounds were synthesised in 60 – 90% yields with 85 -95% purity. The chemical structures of the compounds were characterised using physicochemical techniques such as physical state, colour and melting point; and spectroscopic techniques including ultraviolet (UV), Fourier transform-infrared (FT-IR), nuclear magnetic resonance (NMR), and mass spectrometry (MS). The compounds were tested for their anti-inflammatory activity using lipopolysaccharide Escherichia coli (LPSEc)-induced inflammation in murine macrophages (RAW 264.7). The test concentration range of the compounds was determined from cytotoxicity studies using 3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT). The anti-inflammatory activity of THTPs was evaluated by measuring the nitrite concentration using Griess assay and determination of inflammatory cytokines levels using enzyme-linked immunosorbent assay (ELISA). All the THTPs inhibited the LPSEc-induced nitrite production and reversed the levels of pro-inflammatory cytokines; interleukin (IL)-6, IL-10, tumor necrosis factor-alpha (TNF-α) and granulocyte-macrophage colony-stimulating factor (GM-CSF). The THTPs were further evaluated for phosphoinositol-3-kinases (PI3-K) isoforms (α, β, γ and δ). The compound 2-(3-chloro-2-methylbenzamido)-N-(3-(trifluoromethyl)phenyl)-6,7-dihydrothiazolo[5,4-c]pyridine-5(4H)-carboxamide (TR-6) was found to be the most potent.