Research in Biotechnology, 1: 38‐48, 2010 ISSN: 2229-791X www.researchinbiotechnology.com *Corresponding author : tpsphc@gmail.com Regular Article Synthesis and anti-oxidant activity of novel 6,7,8,9 tetra hydro- 5H-5-(2'-hydroxy phenyl)-2-(4'-substituted benzylidine)- 3-(4-nitrophenyl amino) thiazolo quinazoline derivatives T. Panneer Selvam* 1 , P. Vijayaraj Kumar 2 and A. Siva Kumar 3 * 1 Department of Biotechnology, Acharya Nagarjuna University, Guntur – 522510, Andrapradesh, India 2 School of Pharmacy, UCSI (University College Sadaya International) University, Jalan Menara Gading 56000, Cheras, Kuala Lumpur, Malaysia 3 School of Bio Science and Technology, VIT University, Vellore-632014 Tamilnadu, India In the present study, a series of novel thiazolo quinazoline derivatives were synthesized by condensation of different aromatic aldehydes with 4-nitro aniline. The chemical structures of the synthesized compounds were confirmed by means of IR, 1 H-NMR, mass spectroscopy and elemental analyses. These compounds were screened for anti-oxidant activity by DPPH radical assay, nitric oxide scavenging activity and Hydrogen Peroxide scavenging activity. Among the synthesized compounds 5d, 5c and 5b was found to be the most potent anti-oxidant activity. Key words: Anti-oxidant activity, Benzylidine thiazolo quinazoline, Nitrophenyl amino thiazolo quinazoline, Thiazolo quinazoline Abbreviations: (DPPH) 1, 1-diphenyl-2-picryl-hydrazyl, (DMF) Dimethyl formamide, (NO) Nitric oxide, (ROS) Reactive oxygen species. Free radicals are chemical species containing one or more unpaired electrons, most of them being unstable and capable of abstracting electrons from other molecules. The predominant reactive oxygen species and reactive nitrogen intermediates generated by cell metabolism or by exogenous factors include hydrogen peroxide ( . H 2 O 2 ), the hydroxyl radical ( . OH), the superoxide anion radical . ( - O 2 ), nitric oxide (NO) and peroxynitrite (ONOO - ). Oxygen is critical for life on earth. It is produced by plants during photosynthesis, and is necessary for aerobic respiration for animals. In the last few decades, research on free radicals gained more importance (Halliwell, 2008, Sachdev et al., 2008, Kamat et al., 2006). Oxygen and nitrogen derived free radicals are generated during cellular metabolism and mitochondrial energy production. The oxygen consumption inherent in cell growth leads to the generation of series of reactive oxygen species (ROS). ROS are continuously produced by the body’s normal oxygen usage such as respiration and some cell mediated immune functions. ROS such as hydroxyl ions, superoxide anions, and peroxyl radicals, are involved in oxidative damage to cell components (Gulcin, 2006). ROS may be required for normal cell function at physiological concentrations. The consequence of an imbalance of prooxidants and anti-oxidants in the organism, if ROS are not effectively scavenged by cellular