Objective: To study on the volatile oil components in herbal pair(HP) of Atractylodis Macrocephalae Rhizoma(AMK)-Poria(PCW) and its single herb

and to investigate the different HP proportions on the the volatile oil. Method: Volatile oil was extracted from HP and its single herb by organic-steam distillation. The chemical constituents were analysised and identified by GC-MS technique and combined with mass spectrometry library searching and literature comparison. Result: There were 26

22

30

29 and 41 volatile constituents in AMK

PCW

HP(1∶1)

HP(1∶2) and HP(2∶1)

and 3 common volatile constituents were identified. There were linoleic acid

palmitic acid and α-cedrene. 16 compounds were identified from volatile oil of AMK and the three HP. The top three were (4aS

8aR)-3

8a-dimethyl-5-methylene-4

4a

5

6

7

8

8a

9-octahydronaphtho[2

3-b]furan

(-)-g-elemene

β-panasinsene. And volatile oil of PCW were only six ingredients can be to detect from the three HP

accounts for only 27% of PCW. Conclusion: Regarding the volatile oil components and content

the volatile chemical components in the three HP were mainly from single herb AMK

the volatile oil components of different HP proportions have different degrees of change and the most obvious one is the HP(2∶1). This may be associated with the increased dosage of AMK. And all the three HP have new components detected. The reason may be due to the occurrence of certain physical changes or chemical reactions during the decocting process.