Unique guanidine-conjugated catechins from the leaves of Alchornea rugosa and their autophagy modulating activity

Natural guanidines, molecules that contain the guanidine moiety, are structurally unique and often exhibit potent biological activities. A phytochemical investigation of the leaves of Alchornea rugosa (Lour.) Mull.Arg. by MS/MS-based molecular networking revealed eight undescribed guanidine-flavanol conjugates named rugonines A-H. The chemical structures of the isolated compounds were comprehensively elucidated by NMR spectroscopy, HRESIMS, and circular dichroism (CD) analysis. All isolated compounds were tested for autophagosome for-mation in HEK293 cells stably expressing GFP-LC3. The results revealed that compounds rugonines D-G showed potential autophagy inhibitory activity.