Antioxidant and free radical scavenging activities of taxoquinone, a diterpenoid isolated from Metasequoia glyptostroboides

Abstract

Nowadays, there is an upsurge of interest on finding effective phyto-constituents as new sources of natural antioxidants for using in food and pharmaceutical preparations. However, this study was carried out to investigate the antioxidant and free radical scavenging efficacy of a biologically active diterpenoid compound taxoquinone isolated from Metasequoia glyptostroboides in various antioxidant models. An abietane type diterpenoid taxoquinone, isolated from ethyl acetate cone extract of Metasequoia glyptostroboides, was analyzed for its antioxidant efficacy as reducing power ability and its ability to scavenge free radicals such as 1,1-diphenyl-2-picryl hydrazyl (DPPH), nitric oxide, superoxide and hydroxyl radicals. As a result, taxoquinone showed significant and concentration-dependent antioxidant and free radical scavenging activities of DPPH, nitric oxide, superoxide and hydroxyl free radicals by 78.83%, 72.42%, 72.99% and 85.04%, as compared to standard compounds ascorbic acid (81.69%, 74.62%, 73% and 73.79%) and α-tocopherol/butylated hydroxyanisole (84.09%, 78.61%, 74.45% and 70.02%), respectively. These findings justify the biological and traditional uses of M. glyptostroboides or its secondary metabolite taxoquinone as confirmed by its promising antioxidant and free radical scavenging activities.