Free-Radical–Scavenging Activity in the Infl orescence of European Nettle/Sisnu (Urtica dioica L.)

The inß orescence of Urtica dioica L. is used by ethnic people of Darjeeling Hills as therapeutics and green vegetables. As it is ethnomedicinally very important for curing several critical and emerging oxidative stress– induced diseases, the inß orescence of this plant may be considered as a potential source of antioxidants. In the present study, U. dioica inß orescences were successively extracted and puriÞ ed with nine different solvents by using silica gel column chromatography to study their antioxidant properties and polyphenol contents. Ethyl acetate:acetone::1:3 fraction was found (91.50% inhibition) to be the best scavenger of DPPH at a dose of 100 µg/ ml among 33 extracts, which was comparable with standard quercetin (44.77% inhibition). An NBT-NADH-PMS– based highest superoxide–scavenging activity (53.30% inhibition) was observed in acetone:ethanol::1:1 fraction, which was also comparable with the same standard (72.30%). Optimum anti-lipid peroxidation of 55.27% inhibition was detected in diethyl ether:ethyl acetate::1:1 fraction. TLC Þ ngerprint of ethyl acetate:acetone::1:3 extract after derivatization with DPPH showed maximum number of separated components with the highest diameter at Rf = 0.907. Phenols and ß avonoids were mostly concentrated in the same fraction with a concentration of 24.22 ± 0.26 and 43.34 ± 1.02 mg/g of dry mass, respectively. SigniÞ cant correlations were found among phenolic phytochemicals and radical–scavenging activity through which it may be assumed that the antioxidants present in U. dioica inß orescence are polyphenolic in nature. The observations suggest the importance of ethnomedicinal use of U. dioica, which could be commercially exploited by the pharmaceutical industry as a natural antioxidant.