Building Block-Based Molecular Networking Enables Targeted Isolation of PTP1B-Inhibitory Triterpene-Flavanol Conjugates from the Stems of Tripterygium regelii.

Celastrol, a quinone methide triterpenoid present in plants of the genus Tripterygium, is a potent leptin sensitizer and a promising scaffold for anti-obesity drug development. Metabolite profiling of the stems of Tripterygium regelii using UPLC-qTOF-MS/MS, combined with building block-based molecular networking (BBMN) analysis, led to the isolation of ten previously undescribed triterpene-flavanol conjugates (1-10), including celastrol derivatives, as well as the annotation of 34 additional congeners sharing a similar core scaffold. The structures of compounds 1-10 were elucidated through comprehensive spectroscopic analyses, chemical derivatization, and quantum chemical calculations. All isolates exhibited configurationally stable sp3-sp2 axial chirality at ambient temperature, and both P- and M-configured atropisomers were identified. In vitro evaluation of protein tyrosine phosphatase 1B (PTP1B) inhibition revealed that compound 10 exhibited potent activity, with an IC50 value of 0.6 ± 0.1 μM, acting as a mixed-type inhibitor. These triterpene-flavanol conjugates represent a new structural class with potential as lead compounds for the development of anti-obesity agents.