Molecular docking studies of quercetin and its analogues against human inducible nitric oxide synthase.

Nitric oxide synthases (NOS) catalyze to produce nitric oxide (NO) from L-arginine. The isoform of NOS i.e. inducible nitric oxide synthases (iNOS) expression is observed in various human malignant tumors such as breast, lung, prostate and bladder, colorectal cancer, and malignant melanoma. Also an increased level of iNOS expression and activity has been found in the tumor cells of gynecological malignancies, stroma of breast cancer and tumor cells of head and neck cancer. Because of its importance in causing tumors and cancer, iNOS enzyme has become a new target in finding novel inhibitors as anti cancer agents. The present work focuses on the molecular docking analysis of quercetin and its analogues against iNOS enzyme. Earlier there are reports of quercetin inhibiting iNOS enzyme in certain experiments as anti cancer agent. But the clinical use of quercetin is limited by its low oral bioavailability and therefore needed its molecular modification to improve its pharmacological properties. In the present study ten analogues of quercetin were found to be docked at the active site cavity with favorable ligand-protein molecular interaction and interestingly from the ADME-Toxicity analysis these analogues have enhanced pharmacological properties than quercetin.