He Jianbo¹, Guo Shenglan²，Huang Mingya^2,3 ,Lei Yan^2,3, Guo Chunhua^1*

1 College of Animal & Veterinary science, Southwest Minzu University, Chengdu 610041

2 DadHank (Chengdu) Biotech Corp., Chengdu 611130

3 Sichuan Animal Feeding Regulation Engineering Technology Research Center, Chengdu 611130

Abstract: The in vitro antioxidant activities of 5 natural plant essential oils and 20 essential oils were determined by DPPH radical scavenging method. (And) Then, the IC₅₀ values of 3 essential oils components (citral, cinnamaldehyde and limonene) which were commonly used in production were screened out and their DPPH radical scavenging rate was over 90%.

Results showed: (1) The natural plant essential oil and essential oil composition concentration is 0.2 g/mL, 10 kinds of essential oil including oregano oil, clove oil, lavender oil, cinnamon oil, valerian oil, eugenol, thyme （thymol）, carvacrol, terpineol, vanillin, as well as the positive control substance — 2,6-Di-tertiary butyl-4-methyl phenol (Butylated hydroxytoluene, BHT) on free radical clearance rate is above 90%; The scavenging rates of the three commonly used essential oil components, citral, cinnamaldehyde, and limonene, were 84.793%, 45.548% and 36.207%, respectively. 

2. When the concentration of natural plant essential oils and essential oil components was 0.02 g/mL, 7 types of essential oils including basil oil, clove oil, lavender oil, eugenol, thymol, carvacrol, vanillin and BHT were still had a free radical scavenging rate of over 90%, demonstrating good antioxidant performance. However, cinnamon oil, valerian oil and terpineol showed relatively weak antioxidant performance, with scavenging rates of 48.901%, 38.511% and 43.014%, respectively. 
3. The IC₅₀ values of the 10 essential oils and BHT were: eugenol-0.00793 mg/mL, clove oil-0.01287 mg/mL, lavender oil-0.35802 mg/mL, BHT-0.65943 mg/mL, oregano oil-0.68764 mg/mL, thymol-1.02351 mg/mL, vanillin-1.1483 mg/mL, carvacrol-1.3025 mg/mL, citral-46.6633 mg/mL, cinnamaldehyde-121.34 mg/mL and limonene-231.002 mg/mL. In summary, the eugenol, clove oil, lavender oil, oregano oil, thymol, vanillin and carvacrol have a high level of antioxidant activity. Among them, eugenol, clove oil, and lavender oil are 83.16 times, 51.24 times, and 1.84 times higher than BHT, respectively.

Key words: Essential oils, Antioxidant activity, DPPH free radicals.