Comparative study of the antioxidant activity of forty-five commonly used essential oils and their potential active components

Abstract

This study was to examine the in vitro antioxidant activities of forty-five commonly used essential oils and their major components. The oils and major components were subjected to screening for their possible antioxidant activity by measuring the ABTS+. radical scavenging ability, reducing power and metal chelating activity. The ABTS+. radical scavenging ability and reducing power of cinnamon leaf and clove bud essential oils are the best two among these essential oils. At the concentration of 1 mg/mL, cinnamon leaf (96.45 ± 0.01%) and clove bud (96.33 ± 0.01%) essential oils showed the strongest ABTS+. radical scavenging ability. The EC 50 values of cinnamon leaf and clove bud essential oils are 12 μg/mL and 10 μg/mL, respectively. At the concentration of 10 mg/mL, cinnamon leaf and clove bud essential oils showed reducing power of 119.42 ± 0.68% and 112.92 ± 0.87% relative to butylated hydroxyanisole (BHA), respectively. Eugenol is the main component of cinnamon leaf and clove bud essential oils that contributes significantly to their ABTS+. radical scavenging activity and reducing power. In the metal chelating activity test system, basil essential oil was determined to be 57.48 ± 0.25% and its EC50 value is 984 μg/mL. Methyl chavicol is the major component of the basil essential oil that attributes greatly to its metal chelating activity. The higher phenolic content may explain the higher ABTS +. radical scavenging and reducing power activity of the forty-five kinds of commonly used essential oils. High electron density of the oxygen atom and low steric hindrance of the plane molecule of the methyl chavicol are the two possibilities that account for its higher metal chelating ability.