Abstract

In the present study, antioxidant activity, total phenolic and flavonoid content, and 15-lipoxygenase inhibitory activity of ethanol extract and its ethyl acetate, n-butanol and aqueous fractions of Eucalyptus citriodora kino were evaluated. The antioxidant activity was determined using 2,2-diphenyl-1-picrylhydrazyl and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) methods. The IC50 values of the ethanol extract were 5.11±0.13, 2.72±0.08 and 25.86±1.81 μg/ml in the 2,2-diphenyl-1-picrylhydrazyl, 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) methods and the 15-lipoxugenase assay, respectively. Total phenolic and flavonoid content of the ethanol extract were 490.77±1.95 mg catechin equivalents/g and 21.81±0.23 mg quercetin equivalents/g, respectively. Solvent partition of the ethanol extract yielded ethyl acetate, n-butanol and aqueous fractions. Among the three fractions, the ethyl acetate fraction showed the highest total phenolic and flavonoid contents, which were 575.87±3.92 mg catechin equivalents/g and 34.57±0.30 mg quercetin equivalents/g, respectively. This fraction also showed the strongest free radical scavenging activity in the two methods used as well as inhibitory activity against 15-lipoxygenase, with IC₅₀ values of 4.67±0.09, 2.57±0.06 and 14.67±0.93 μg/ml, respectively. These findings revealed that high antioxidant and lipoxygenase inhibitory activity of E. citriodora kino might be due to high phenolic and flavonoid content. These results showed that E. citriodora kino could be a potential source of natural antioxidants and lipoxygenase inhibitors which could be used to prevent free radical and lipoxygenase mediated diseases.