Antioxidant Activities of the Phenolic Extracts of Seed Oils and Seed Hulls of Five Plant Species

Antioxidant activities of the phenolic extracts of seed oils and seed hulls of five plant species were compared with those of butylated hydroxyl toluene (BHT) solutions at comparable phenolic concentrations in order to understand the phenolic dependence of the antioxidant activity and to evaluate the potentials of these phenolic extracts as alternatives for synthetic antioxidants. For this purpose, colorimetrically determined total phenol contents of the plant extracts were adjusted to known concentrations by suitable dilutions and the solutions of BHT with comparable concentrations were prepared by diluting a stock solution. The correlations of the total phenol contents and o-diphenol contents with the antioxidant activities of the phenolic extracts were also tested. Antioxidant activities of the phenolic extracts from different plants varied even at equal total phenol concentrations. o-Diphenol contents showed better correlations with the antioxidant activities than total phenol contents. A clear idea about the antioxidant potentials and the dependence of antioxidant activities on the quality and the quantity of phenolic substances can be obtained by comparison of the antioxidant activities of different phenolic extracts at equal total phenol concentrations.