A Simple, Rapid, and Practical Method for Distinguishing Lonicerae Japonicae Flos from Lonicerae Flos

Lonicerae japonicae flos (LJF), the dried flower buds of Lonicera japonica Thunb., are often adulterated with Lonicerae. flos (LF), which is derived from the other four Lonicera species. Scholars at home and abroad have established several analytical methods to distinguish LJF from the four Lonicera species of LF; however, to date, no effective and practical method has been established for distinguishing LF from LJF. In our present study, the HPLC fingerprints of LJF and LF were compared, and differences in the content of one of the iridoids were found. Column chromatography combined with pre-HPLC was used for isolating and preparing the iridoid, and its structure was identified as secologanic acid. Then, a method for determining the content of secologanic acid was established using HPLC. The amounts of secologanic acid in 34 batches of LJF and 38 batches of LF were determined. The average amount of secologanic acid in 34 batches of LJF was 18.24 mg/g, with values ranging from 12.9 mg/g to 23.3 mg/g, whereas the average amount in 38 batches of LF was 1.76 mg/g, with values ranging from 0.2 mg/g to 7.2 mg/g. Therefore, secologanic acid can be considered as one of the characteristic components for distinguishing LJF and LF. Our study not only provides a rapid, simple, sensitive, and practical method for identifying LJF and LF but also establishes a method for discovering the characteristic components of other herb-medicines that are susceptible to adulteration.