Potential food additives from Carex distachya roots: identification and in vitro antioxidant properties

In the present study, the chemical composition and antioxidant properties of root methanol extract of Carex distachya Desf. (Cyperaceae) were assessed to use this plant as sources of food additives and nutraceuticals. The IC50 of the extract (4.2 microg/mL), derived from the DPPH radical scavenging capacity assay, was similar to those of ascorbic acid, alpha-tocopherol, and BHT. These results revealed a strong antioxidant activity because of the presence of an extraordinary quantity of bioactive phytochemicals. The phytochemical study of the root extract led to the isolation and identification of new and known polyphenols, most of them common constituents of plant foods. A total of 16 polyphenols, identified on the basis of spectroscopic data as 7 lignans, 4 phenylethanoids, 3 resveratrol derivatives, a monolignol, and a secoiridoid glucoside, were isolated. The tentative structural elucidation of the new metabolites 5'-O-beta-D-glucopyranosyloxy-3,3'-dimethoxy-7,9'-epoxylignan-4,8',9-triol and 3,5-bis-O-beta-D-glucopyranosyloxy-3'-methoxy-trans-stilben-4'-ol have been performed by a combined approach using ESI/TQ/MS techniques and 1D and 2D NMR experiments. All of the compounds have been tested for their antioxidant activity using six different antioxidant and radical scavenging tests. Interestingly, the extract contained high quantities of polyphenols, most of them reported as constituents of edible plants, such as grape and olive, suggesting that the methanol root extract of this plant could be used as a source of natural antioxidants useful as potential food additives.