Screening of antioxidant activity and phenolic content of 24 medicinal plant extracts

Abstract

Background: Antioxidants are vital substances which possess the ability to protect the body from damages caused by free radical-induced oxidative stress. A variety of free radical scavenging antioxidants are found in dietary sources like fruits, vegetables and tea. The purpose of this study was to evaluate the antioxidant activity of methanolic extracts of 24 selected plant materials (seeds or fruits), which are used by Iranian people as folk remedies and/or food supplements.

Methods: The antioxidant activity was evaluated against linoleic acid peroxidation using 1,3-diethyl-2-thiobarbituric acid as reagent. At the same time the phenolic content of the extracts was determined using Folin-Ciocalteau reagent to evaluate their contribution to total antioxidant activity.

Results: The antioxidant activity expressed as IC₅₀ ranged from 1.25 mg/ml in cucumber to 167.29 mg/ml in cardamom. Phenolic contents, expressed as gallic acid equivalents, varied from 21.76 mg/100g of the dried weight in linseed to 919.12 mg/100 g of the dried weight in Bishop's weed. No significant correlation was observed between antioxidant activity and phenolic content in the studied plant materials.

Conclusion: The results of this study showed that there is no significant correlation between antioxidant activity and phenolic content of the studied plant materials and phenolic content could not be a good indicator of antioxidant capacity.