Achillea tenuifolia (AT) is one of the most herbs are being used by people as a traditional medicinal remedy. Antioxidant activity of AT different extracts and total flavonoid and phenol levels in the extracts were investigated in this study. Plant extracts were prepared by maceration method using ethyl acetate, methanol and methanol-water (1:1). Folin Ciocalteu reagent in terms of gallic acid equivalent achieved the total phenol's content. AlCl3 was used as a reagent for flavonoid determination. Flavonoid content of the plant extracts obtained in terms of quercetin equivalent. DPPH radical scavenging effect of the extracts was determined by UV spectroscopy. Also in order to determine lipid peroxidation inhibition of the extracts of A. tenuifolia, ferric thiocyanate method with BHT, a synthetic reference standard, was carried out in this study. Phenol contents were 43.97 ± 0.034, 74.16 ± 0.55 and 106 ± 0.693 mg g-1 in the ethyl acetate, methanol and methanol-water extracts, respectively. Flavonoid amount obtained in the ethyl acetate, methanol and methanol-water extracts were 10.6 ± 1.85, 23.1 ± 0.5 and 190 ± 1.3 mg g-1, respectively. The percentage of DPPH radical scavenged by the most active extract (methanol-water) of A. tenuifolia was 92% at a concentration of 1 mgml-1 greater than 94% of BHT at 2 mgml-1. IC50 of methanol-water extract and BHT were 0.015 and 0.053 mgml-1, respectively. Lipid peroxidation inhibition was observed by the most polar extract of AT about 91.84%. Phenol and flavonoids content confirm the existence of more polar hydroxyl containing chemical structures in the plant. The potency of radical scavenging effect of methanol-water extract was about 3.5 times greater than synthetic antioxidant BHT. The inhibitory activity of the extracts on the lipid peroxidation of linoleic acid in ferric thiocyanate test was also significant (> 90%). In this study we concluded that there is a direct relation between phenol and flavonoid content of plant extracts and the antioxidant activity. So that the greater amount of phenolic compounds leads to more potent radical scavenging and lipid peroxidation inhibition activities as it was observed in A. tenuifolia polar extract in the present study.
Key words: Flavonoids, phenols, Achillea tenuifolia, DPPH, lipid peroxidation.
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