Chemical composition and synergistic antioxidant activities of essential oils from Atractylodes macrocephala and Astragalus membranaceus.

Chemical composition of the essential oils derived from Atractylodes macrocephala (AMA), Astragalus membranaceus (AME) and AMA-AME herb pair was investigated using gas chromatography-mass spectrometry (GC-MS). Antioxidant activities were evaluated by 1,1-diphenyl-2-picyrlhydrazyl (DPPH) radical-scavenging and Trolox equivalent antioxidant capacity (TEAC) assays. Forty-five, ten and forty-three components were identified in AMA, AME and AMA-AME essential oils, respectively. AMA-AME essential oil exhibited a significantly higher radical scavenging capacity than the theoretical sum of those of the respective herb essential oils (P < 0.05). Principal component analysis showed that twenty-three components contributed to the scavenging activities against DPPH and ABTS*+ radicals. Moreover, the concentrations of these major components exhibited various increases to some extent when compared with the theoretical sum of the respective herb essential oils. These findings suggest that combination of two or more herbs might be used as a promising source of natural antioxidants in the pharmaceutical and food industries.