Abstract

Nitric oxide is generated in almost all the tissues of the mammalian system however, under pathological conditions NO has damaging effects. Its increased concentration, under various neural diseases leads to cell damage through formation of highly reactive peroxynitrite. Cysteine proteinase inhibitors are of prime physiologic importance inside the cells, controlling the activities of lysosomal cysteine proteases. They prevent unwanted proteolysis and are involved in several neurodegenerative diseases. Our present study was designed to investigate the protective effect of curcumin and quercetin against NO induced damage of buffalo brain cystatin (BC) and to evaluate antinitrostative efficacy of curcumin and quercetin. Nitric oxide induced structural modifications were followed by fluorescence spectroscopy and functional inactivation by monitoring the inhibition of caseinolytic activity of papain. 50 μM sodium nitroprusside (SNP used to produced NO) caused time dependent inactivation of BC with complete functional loss precipitating at 150 min. Curcumin (50 μM) and quercetin (250 μM) opposed such loss in papain inhibitory activity of BC. Loss in tertiary structure of BC (fluorescence quenching) was observed on exposure to NO. Inhibition of functional and structural SNP mediated damage of BC by curcumin (50 μM) and Quercetin (250 μM) reaffirms their NO scavenging potency.

By the results obtained, it was concluded that curcumin and quercetin were able to protect BC against structural and functional damage to a very considerable level. Thus, in view of this study, it can be elucidate that Curcumin and quercetin have a significant potential in the treatment of diseases caused by nitrogen free radicals and this potential must be further explored for the development of novel drugs.

Keywords: Curcumin, nitric oxide, purification of Buffalo brain cystatin, quercetin, Thiol proteinases inhibitor, mammalian, pathological conditions, Cysteine proteinase inhibitors, peroxynitrite, Griess Reaction, nitrogen species, DNA