# Comparison and Identification of the Aroma-Active Compounds in the Root of _Angelica dahurica_
## 2 Results and Discussion
### Key Aroma-Active Compounds Identified by SPME-AEDA  
To further explore the key aroma-active compounds in the root of _A. dahurica_, dilution analysis was performed using SPME in conjunction with AEDA. As shown in Table 2, there were 12, 16, and 15 compounds that contributed to odors of in Hangbaizhi, Qibaizhi, and Bobaizhi, respectively, as determined by the sniffing test. The FD factor reflects the magnitude of the contribution of each aroma compound: A high FD factor corresponds to a greater contribution to the flavor of _A. dahurica_. As shown in Table 2, the FD value of prenol (herbal) was higher in Hangbaizhi (FD = 81) than in the other samples. Nonanal (citrusy) and \(\alpha\)-copaene (woody) (FD = 27), as well as acetic acid (sour) and \(\beta\)-pinene (pine) (FD = 9), contributed substantially to the flavor of Hangbaizhi. Hence, these five compounds were key aroma-active compounds in Hangbaizhi. Sixteen aroma-active compounds were detected in Qibaizhi by the sniffing test. Prenol (herbal) (FD = 81), (-)-\(\beta\)-elemene (spicy) (FD = 81), \(\beta\)-pinene (pine) (FD = 27), \(\gamma\)-muurolene (herbal) (FD = 27), acetic acid (sour) (FD = 9), carophyllene (woody) (FD = 9), and humulene (woody) (FD = 9) were key aroma-active compounds in Qibaizhi. Fifteen aroma compounds, including \(\alpha\)-gurjunene (woody) (FD = 81), prenol (herbal) (FD = 81), \(\alpha\)-copaene (woody) (FD = 27), nonanal (citrusy) (FD = 27), 2-methyl-2-butenal (fruity) (FD = 9), acetic acid (sour) (FD = 9), aromadendrene (woody) (FD = 9) and \(\beta\)-pinene (pine) (FD = 9), were identified in Bobaizhi, indicating that they were key aroma-active compounds in Bobaizhi. Compounds with FD \(\leq\) 3 were considered to be minor contributors to the overall aroma, but these compounds did enhance the complexity of _A. dahurica_ in some ways. SPME-AEDA indicated that the key aroma-active compounds in the three types of _A. dahurica_ were similar; however, some compounds had different FD factors. For example, the FD value of 2-methyl-2-butenal (fruity) (FD = 9) in Bobaizhi was higher than those in Hangbaizhi (FD = 1) and Qibaizhi (FD = 1). The FD values of \(\beta\)-pinene (pine) (FD = 27), (-)-\(\beta\)-elemene (spicy) (FD = 81), and carophyllene (woody) (FD = 9) in Qibaizhi were higher than those in Hangbaizhi (FD = 9, 1, and 3 for \(\beta\)-pinene, (-)-\(\beta\)-elemene and caryophyllene, respectively) and Bobaizhi (FD = 9, 1, and 1, for \(\beta\)-pinene, (-)-\(\beta\)-elemene and caryophyllene, respectively). The FD value of nonanal (citrusy) (FD = 1) in Qibaizhi was lower than those in Hangbaizhi (FD = 27) and Bobaizhi (FD = 27). Among all, the intensity of the volatile compounds on the _A. dahurica_ samples have not been studied yet. As shown in Table 3, the external standard method was used to accurately quantify ten key aroma-active compounds shared by Hangbaizhi, Qibaizhi, and Bobaizhi as identified by SPME-AEDA. It can be seen from the table that the same aroma compounds had different FD values in the different _A. dahurica_ cultivars due to the difference in their concentrations. These common aroma-active compounds provided the three kinds of _A. dahurica_ with similar odor properties, but because of their different concentrations in each sample, they contributed to the overall odors to different extents. In addition to these ten common aroma compounds, the three kinds of _A. dahurica_ each had several unique aroma-active compounds. For example, \(\gamma\)-muurolene (herbal) and humulene (woody) were key aroma-active compounds characteristic of Qibaizhi, and \(\alpha\)-gurjunene (woody) was an aroma-active compound unique to Bobaizhi. These differences may have caused differences in the overall odors of these three kinds of _A. dahurica_.