Chiang Mai Journal of Science

 Eucalyptus essential oils are widely known to use in various application such as traditional medicine, food, cosmetic and botanical insecticide. This study is to evaluate antioxidant capacity of essential oils hydrodistillated from the leaves of six half-sib families of Eucalyptus camaldulensis Dehnh. planted in Nakhon Ratchasima province, Thailand. and to analyze the antioxidative component of essential oils by Gas Chromatography - Mass Spectrometry (GC/MS) method. The clear and yellowish essential oils were obtained in 1.14-2.07% yield based on the dry leaf basis. The results of the antioxidant activities revealed four Eucalyptus oils from leaves of half-sib families 109, 188, 208 and 209 of E. camaldulensis inhibited significant effect with free radical (DPPH) scavenging, IC₅₀ values in the range between 0.71-1.27 (mg/mL), TEAC values ranging of 22.20-25.17 mM/g and FRAP values ranging of 291.80-676.48 mM Fe(II)/g. The high amount of phenolic terpenoids (2.18-7.25%), thymol and carvacrol together with dominant compositions of p-cymene (10.71-28.25%), γ-terpinene (5.58-40.86%) and terpene alcohols (15.21-29.19%) may cause these oils showing potent antioxidant activity. Therefore, the sample trees of these half-sib families of E. camaldulensis could be vegetatively propagated as clones to use their leaves as a new potential source of natural antioxidants in industrial to enhance the commercial plantation.