In vitro antioxidant and free radical scavenging activity of four Alkanna species growing in Iran

BACKGROUND: Medicinal plants are recognized as sources of natural antioxidants that can protect biological system from oxidative stress. OBJECTIVE: In this study, the antioxidant activities of four species of the Alkanna genus (Alkanna bracteosa, Alkanna frigida, Alkanna orientalis and Alkanna tricophila) were evaluated. MATERIALS AND METHODS: The dried roots of plant samples (100 g) were extracted separately by percolation method with MeOH/H(2)O (80/20) and four fractions were provided respectively with hexane, chloroform, ethyl acetate, butanol and water. Antioxidant activities were investigated by using 1,1-diphenyl-2-picrylhydrazyl, ferric thiocyanate and thiobarbituric acid methods and compared with quercetin (as positive control). RESULTS: The results indicated that the butanol fractions of four species had the highest antioxidant activity and radical scavenging activity compared with the other fractions studied (P < 0.05). The 50% effective concentration (half - effective doses) values of butanol fractions are less than quercetin and other fractions, so, these fractions showed potent antioxidant activity. This indicated that the active compounds in the root parts of Alkanna species dissolved in the butanol. All the fractions of four species of Alkanna had antioxidant activity, while, there were no significant differences (P > 0.05) between the total antioxidant activities of same fractions. The total antioxidant activity values of Alkanna fractions in a descending order are as follows: Butanol fraction > ethyl acetate fraction > total extract > hexane fraction > chloroform fraction > aqueous fraction. CONCLUSION: The antioxidant activities of butanol fractions of samples were higher than quercetin. This may be because most of the active compounds of Alkanna species dissolved in the butanol.