Metabolomics-guided discovery of previously undescribed lupane-type triterpenoids with anti-inflammatory activity from Mallotus repandus (Willd.) Müll. Arg.

Guided by molecular networking based on liquid chromatography with tandem mass spectrometry (LC-MS/MS), nine previously undescribed lupane-type triterpenoids (1-9), together with six known analogs (10-15), were isolated from the 95% ethanol extract of the stems and leaves of Mallotus repandus (Willd.) Müll. Arg. Their structures were delineated using a combination of high-resolution electrospray ionization mass spectrometry (HRESIMS) data, nuclear magnetic resonance (NMR) spectroscopy, and quantum-chemical electronic circular dichroism (ECD) calculations. Notably, compounds 1 and 2 are the first reported 29,30-dinorlupane-type triterpenoids in nature, and compounds 3 and 4 are relatively rare 30-nor-lupane-type triterpenoids. Additionally, most of these isolates were evaluated for their ability to inhibit lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW264.7 murine macrophage cells. Among them, compounds 2, 11, and 15 showed the most potent activity with IC50 values of 11.96, 19.13, and 17.07 μM, respectively. Moreover, compound 2 exhibited a dose-dependent suppression of IL-6 and TNF-α levels.