Characterization and antioxidant activity of essential oils from fresh and decaying leaves of Eucalyptus tereticornis

Abstract

The composition of essential oils hydrodistilled from fresh and decaying leaves of Eucalyptus tereticornis was analyzed by means of gas chromatography and mass spectrometry, and a total of 68 constituents were identified. The essential oils were assayed for antioxidant activity in terms of scavenging of 2,2-diphenyl-1-picrylhydrazil (DPPH) and hydroxyl (OH•) radical, and superoxide anion (O₂^-•).The major constituents of the fresh leaf oil were α-pinene (28.53%) and 1,8-cineole (19.48%), whereas in the decaying leaf oil, β-citronellal (14.15%), (-)-isopulegol (13.35%), and (+)-β-citronellol (10.73%) were the major components. Both essential oils exhibited a strong radical scavenging activity against DPPH radical with IC₅₀ values of 110 and 139.8 μg/mL for fresh and decaying leaf oil, respectively (IC₅₀ of BHT = 164.2 μg/mL). Further, the essential oils (at 400 μg/mL) also exhibited OH• (56-62%) and O^2-• (65-69%) scavenging activity parallel to the commercial antioxidant BHT/ascorbic acid. However, unlike the essential oils, the major monoterpene constituents exhibited significantly less scavenging activity (<35% DPPH or OH•; at 400 μg/mL). The study concluded that fresh and decaying leaves of E. tereticornis are a source of monoterpenoid rich oil exhibiting antioxidant activity.