Quality evaluation of Angelicae acutilobae radix: individual differences and localization of (Z)-ligustilide in Angelica acutiloba root

It has been difficult to evaluate the quality of Angelicae acutilobae Radix (Toki) because of large differences in the contents of its chemical constituents. In this research, we revealed individual differences and localization of (Z)-ligustilide in Toki cultivated and processed under the same conditions. Thirteen Toki samples (dry weight: 68.2 g–132.3 g) were divided and categorized into 13 parts and the (Z)-ligustilide content of each part was quantified. Total (Z)-ligustilide content ranged from 0.08% to 0.22% and the maximum difference between samples was approximately 2.8-fold. In addition, the localization of (Z)-ligustilide was examined. (Z)-Ligustilide content was the highest in lateral root at 0.19%, followed by main root at 0.13%, and the lowest in root head at 0.09%. Furthermore, the content tended to increase as the root became thinner. In particular, the difference in content between the inner side of upper root head (removed 5 mm from the epidermis 0.06%) and the 1.1–3.0 mm in diameter lateral root (0.24%) was largest at approximately 4.1-fold. We revealed that not only differences among individuals but also localization is a factor affecting the quality of Toki. In contrast, individuals with higher root part (main root + lateral root) weight ratio in whole root dry weight had higher (Z)-ligustilide content. The difference in (Z)-ligustilide content among individuals is due to the balance between root head part and root other than head part. It is possible to predict (Z)-ligustilide content from weight ratio of root part to whole root.