Antioxidant activity of tuberosin isolated from Pueraria tuberose Linn.

Antioxidant activity of Pueraria tuberose DC, (PT) Leguminosae (Fabaceae) has already been reported by us and here an active compound has been isolated and its action on expression of iNOS protein has been explored by using LPS induced changes in attached rat peritoneal macrophage cell culture. The pure compound was isolated by column chromatography and its structure was characterized by spectral studies, which was identified as tuberosin (5 hydroxy 3,4,7,3',4' pentamethoxy flavone). Its antioxidant capacity was determined and compared with alcoholic extract as EC50 value for scavenging potential towards pre-generated monocation ABTS* radical, superoxide radicals, hydroxyl radicals, metal chelation property and on lipid peroxidation. Further, rat peritoneal macrophages were isolated, cultured and the attached macrophages were exposed to lipopolysaccharide (LPS) with different concentrations of tuberosin (pretreatment for 30 min). After 17 h the released NO content, in culture supernatant, was indirectly estimated as accumulated nitrite by Griess reagent. To understand the mechanism of action, the extent of expression of inducible nitric oxide synthase genes, the iNOS protein was assessed in macrophage lysate by using its antibody on western blot analysis. Tuberosin significantly scavenged all the species of FRs, described above and it also inhibited the LPS induced release of NO and amount of iNOS protein in macrophages. All the changes were significant and concentration dependent. Thus it could be suggested that tuberosin, is one of the active principles of Pueraria tuberose, which directly scavenges various species of Free radicals (FRs) and also inhibits LPS induced inflammatory changes in macrophages.