Antioxidative capacity of rhizome extract and rhizome knot extract of edible lotus (Nelumbo nuficera)

Extracts from rhizomes (Lotus roots) knot (LRK) and whole rhizomes (LR) were investigated for their antioxidative capacity in comparison with commonly used antioxidants from plant material. Radical scavenging activity was measured spectrophotometrically using the stable radicals 1-diphenyl-2-picrylhydrazyl and 2,2′-azino(3-ethylbenzothioazolino-6-sulfonate), and measured by electron spin resonance (ESR) trapping of the transient carbon-centered 1-hydroxyethyl radical (generated in a Fenton-type reaction). Efficiencies as chain-breaking antioxidants were evaluated by electrochemical measurement of oxygen consumption rate in a peroxidating methyl linoleate emulsion. LRK exhibited high antioxidative capacity, as measured by each of four different methods. LR, however, only showed a significantly high scavenging activity for small carbon-centered radicals, as measured by the ESR method. Total phenol content in the plant extract correlated with the antioxidant capacity, except for the scavenging of carbon-centered radical. Lotus rhizomes knot, as a waste from food production, will be a potential material for extracting antioxidants.