Antioxidant evaluation of polyhydroxylated nerolidols from redroot pigweed (Amaranthus retroflexus) leaves

Amaranthus retroflexus L., also known as redroot pigweed, is an invasive and cosmopolite plant belonging to Amaranthus genus, anciently used as food sources. From the methanolic extract of the redroot pigweed leaves, several new polyhydroxylated terpenes with a nerolidol skeleton have been isolated and characterized. In this study the antioxidant activity of the methanolic extract of the plant, as well as of its terpene constituents, has been evaluated. The antioxidant properties of each metabolite were evidenced by evaluating their ability to scavenge the DPPH radical and the pro-oxidant hydrogen peroxide as well as by assessing their capacity to inhibit the formation of thiobarbituric acid reactive species (TBARS), and to induce the formation of a phosphomolybdenum complex. The methanolic extract of the plant showed a strong dose-response antioxidant activity, while the pure nerolidol derivatives showed antioxidant capacities comparable to those exercised by the standard α-tocopherol.