## 2 Results and Discussion
### Identification of Absorbed Constituents in Rabbit Plasma and CSF by HS-SPME-GC-MS
#### 2.2.2. Characterization of Eight Absorbed Lignans of AR by HPLC-APCI-IT-TOF-MS\({}^{n}\)  
Most lignans in AR belong to furofuran type. The structure skeleton, common substituent groups and diagnostic fragment ions of this type lignan are summarized in Table 3 according to our research and literature data [13, 14, 15, 16]. _Identification of **L1**, **L2**, **L5**. All of them showed [M+H]\({}^{+}\) at _m/z_ 359.14, and the base peak ion in MS was at _m/z_ 341.14, indicating that their molecular formulae were C\({}_{20}\)H\({}_{22}\)O\({}_{6}\). In MS\({}^{2}\) spectra of them, the diagnostic ions at _m/z_ 291.10 (C\({}_{19}\)H\({}_{15}\)O\({}_{3}\), [M+H-2H\({}_{2}\)O-CH\({}_{3}\)OH]\({}^{+}\)), _m/z_ 259.07 (C\({}_{18}\)H\({}_{11}\)O\({}_{2}\), [M+H-2H\({}_{2}\)O-2 CH\({}_{3}\)OH]\({}^{+}\)), and _m/z_ 137.06 (C\({}_{8}\)H\({}_{9}\)O\({}_{2}\)) indicated that two aryl groups in **L1**, **L2** and **L5** were _o_-methoxy hydroxyyphenyl. Further, **L5** was confirmed to be epipinoresinol by comparison with the reference compound, and **L1** and **L2** were tentatively identified as epipinoresinol isomers. _Identification of **L3** and **L10**. The base peak ions of them were _m/z_ 339.12 in MS, and the diagnostic ions of two aryl groups were observed at _m/z_ 135.04 (C\({}_{8}\)H\({}_{7}\)O\({}_{2}\)) and _m/z_ 137.06 (C\({}_{8}\)H\({}_{9}\)O\({}_{2}\)), accompanied with the ion at _m/z_ 289.09 [M+H-2H\({}_{2}\)O-CH\({}_{3}\)OH]\({}^{+}\) in MS\({}^{2}\). This indicated that one aryl was _o_-methoxy hydroxyyphenyl and the other was 3,4-methylenedioxyphenyl. Accordingly, **L10** was \begin{table}
\begin{tabular}{c c c c} \hline R\({}_{1}\) & R\({}_{2}\) & R\({}_{1}\) diagnostic ion & R\({}_{2}\) diagnostic ion & MS base peak ion [M+H–H\({}_{2}\)O]\({}^{+}\) \\  & & 135.04 (C\({}_{8}\)H\({}_{7}\)O\({}_{2}\)) & 135.04 (C\({}_{8}\)H\({}_{7}\)O\({}_{2}\)) & 337.10 (C\({}_{20}\)H\({}_{17}\)O\({}_{5}\)) \\  & & 135.04 (C\({}_{8}\)H\({}_{7}\)O\({}_{2}\)) & 137.06 (C\({}_{8}\)H\({}_{9}\)O\({}_{2}\)) & 339.12 (C\({}_{20}\)H\({}_{19}\)O\({}_{5}\)) \\  & & 137.06 (C\({}_{8}\)H\({}_{9}\)O\({}_{2}\)) & 137.06 (C\({}_{8}\)H\({}_{9}\)O\({}_{2}\)) & 341.14 (C\({}_{20}\)H\({}_{21}\)O\({}_{5}\)) \\  & & 123.04 (C\({}_{7}\)H\({}_{7}\)O\({}_{2}\)) & 123.04 (C\({}_{7}\)H\({}_{7}\)O\({}_{2}\)) & 313.10 (C\({}_{18}\)H\({}_{17}\)O\({}_{5}\)) \\  & & 151.07 (C\({}_{9}\)H\({}_{11}\)O\({}_{2}\)) & 151.07 (C\({}_{5}\)H\({}_{11}\)O\({}_{2}\)) & 369.17 (C\({}_{22}\)H\({}_{25}\)O\({}_{5}\)) \\  & & 137.06 (C\({}_{8}\)H\({}_{9}\)O\({}_{2}\)) & 167.07 (C\({}_{5}\)H\({}_{11}\)O\({}_{3}\)) & 371.15 (C\({}_{21}\)H\({}_{23}\)O\({}_{6}\)) \\  & & 135.04 (C\({}_{8}\)H\({}_{7}\)O\({}_{2}\)) & 167.07 (C\({}_{5}\)H\({}_{11}\)O\({}_{3}\)) & 369.13 (C\({}_{21}\)H\({}_{21}\)O\({}_{6}\)) \\  & & 135.04 (C\({}_{8}\)H\({}_{7}\)O\({}_{2}\)) & 153.05 (C\({}_{8}\)H\({}_{9}\)O\({}_{3}\)) & 355.12 (C\({}_{20}\)H\({}_{19}\)O\({}_{6}\)) \\ \hline \end{tabular}
\end{table} 
Table 3: The structure skeleton, common substituent groups and diagnostic positive APCI-MS\({}^{n}\) fragment ions of furofuran lignans. identified as xanthoxylol by comparison with the reference compound, and **L3** was tentatively identified as a xanthoxylol isomer. _Identification of **L8**_. It showed [M+H]\({}^{+}\) at _m/z_ 387.14, and the base peak ion in MS was at _m/z_ 369.13, indicating that its molecular formula was C\({}_{21}\)H\({}_{22}\)O\({}_{7}\). The diagnostic ions of two aryl groups were observed at _m/z_ 135.04 (C\({}_{8}\)H\({}_{7}\)O\({}_{2}\)) and _m/z_ 167.07 (C\({}_{9}\)H\({}_{11}\)O\({}_{3}\)), accompanied with the ion at _m/z_ 319.10 [M+H-2H\({}_{2}\)O-CH\({}_{3}\)OH]\({}^{+}\) in MS\({}^{2}\). This indicated that one aryl was _o_-methoxy dihydroxyphenyl and the other was 3,4-methylenedioxyphenyl. Therefore, **L8** was tentatively identified as (1\(R\),2\(S\),5\(R\),6_R_)-5\({}^{\prime}\)-_O-methylpluvialiol [17], which was isolated from _Asarum sieboddii_. _Identification of **L14** and **L15**_. **L15** was confirmed to be _l_-asarmin by comparison with reference compound.