Structural characterization and discrimination of Ophiopogon japonicas (Liliaceae) from different geographical origins based on metabolite profiling analysis

The root tuber of Ophiopogon japonicus (Thunb.) Ker-Gawl ("Maidong" in Chinese), with steroidal saponins and homoisoflavonoids as its representative chemical compositions, is a representative medicinal herbs with multiple major producing areas. This study aimed to distinguish the O. japonicas samples from Zhejiang and Sichuan by using an ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC/Q-TOF MS)-based metabolome analysis. Firstly, a global chemical constituent identification of O. japonicas was carried out by using both automatic and manual methods. An integrated steroidal saponins structural identification strategy in O. japonicas based on exact mass information, fragmentation characteristics and retention time was developed. Overall, 135 steroidal saponins, 47 homoisoflavonoids and 9 other metabolites were quickly identified or tentatively identified from the MSE continuum data. Furthermore, multivariate statistical analysis revealed that O. japonicas from Zhejiang and Sichuan can clearly be separated and some markers were screened. Moreover, some major active components including total soluble sugar, total soluble polyphenol, total flavonoid, total saponin and 10 specific compounds were analyzed quantitatively. In general, these results showed that there were many differences between the metabolic profile data of O. japonicas from different producing areas, O. japonicas from Sichuan showed higher level steroidal saponins and samples from Zhejiang had higher contents of homoisoflavonoids specifically, and indicated that metabolite profiling by UPLC/Q-TOF MS is an effective approach for the discrimination of medicinal herbs from different geographical origins.