Characterization and Antioxidant Activity of Essential Oils from Fresh and Decaying Leaves of<i>Eucalyptus tereticornis</i>

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 O2−• (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.