## 2 Results and Discussion  
### Identification of Absorbed Constituents in Rabbit Plasma and CSF by HS-SPME-GC-MS  
HS-SPME was chosen as the extraction mode because in this mode the SPME fiber can avoid the direct contact with biological samples, which can protect the fiber and prolong the fiber lifetime. Figures 1-4 show the total ion chromatograms of the analyzed samples. In total, 26 absorbed constituents containing 14 monoterpenes (**G1**-**G13**, **G15**), six phenylpropanoids (**G16**, **G18**, **G21**, **G24**-**G26**), four benzene derivatives (**G14**, **G17**, **G20**, **G22**) and two alkanes (**G19**, **G23**) were identified in the plasma and CSF from the AR EtOAc extract group compared with the blank group. The results are summarized in Table 1 and Figure 5.  
Figure 3: Total ion chromatograms of plasma obtained from (**a**) blank group and (**c**) Asari Radix et Rhiz (AR) powder group using HS-SPME-GC-MS.  
Figure 2: Total ion chromatograms of cerebrospinal fluid (CSF) obtained from (**a**) blank group and (**b**) AR EtOAc extract group using HS-SPME-GC-MS. The AR EtOAc extract was reported to be the effective part of AR in analgesic activity [11], thus this extract was selected to study the absorbed constituents of AR after intranasal administration. Among the 26 absorbed constituents identified in the AR EtOAc extract group, 25 constituents were found in the plasma except _p_-cymen-8-ol, whereas 25 constituents were detected in the CSF aside from estragole. Since AR is usually used in the form of powder in TCM nasal therapy clinically, the absorbed constituents after intranasal administration of AR powder were also studied and the absorbed constituents are supposed to be the effective substances of AR when it is used in nasal therapy. In the AR powder group, eight absorbed constituents (eucarvone, _l_-borneol, 3,5-dimethoxyytoluene, safrole, 3,4,5-trimethoxytoluene, methyleugenol, 2,3,5-trimethoxytoluene and asaricin) were identified in the plasma and six of them (except safrole and asaricin) were detected in the CSF. Identification of Absorbed Constituents in Rabbit Plasma and CSF by HPLC-APCI-IT-TOF-MS\({}^{\text{n}}\)  
To reveal more constituents that could be absorbed into plasma and CSF, LCMS-IT-TOF was employed. Both APCI and ESI sources were tested in positive and negative ion modes. It was found that APCI gave stronger ion signals in positive ion mode. Hence APCI was selected as the ion source in the subsequent experiments monitored in the positive ion mode. The fragmentation behaviors of four reference compounds (for their names see 2.2.1 below) in APCI-MS\({}^{\text{n}}\) were studied at first in order to facilitate the structure characterization of the absorbed  
Figure 4: Total ion chromatograms of cerebrospinal fluid (CSF) obtained from (**a**) blank group and (**c**) Asari Radix et Rhiz (AR) powder group using HS-SPME-GC-MS.  
constituents. Afterwards, the absorbed constituents were identified or tentatively characterized by the following procedures: (1) compare the base peak chromatograms (BPCs) of the experimental groups with that of the blank group to find characteristic peaks of them; (2) confirm the existence of them by comparing their characteristic extracted ion chromatograms (EICs) among 3 groups; (3) predict their formulae by high resolution MS data obtained by IT-TOF; (4) elucidate their structures by high resolution IT-TOF MS\({}^{\text{n}}\) data and by comparison with literature; (5) confirm their structures by comparison with the reference compounds as far as possible.