Belamchinanes A-D (1-4), four triterpenoids with an unprecedented skeleton, were isolated from the seeds of Belamcanda chinensis and fully characterized. The structures of belamchinanes feature a 4/6/6/6/5 polycyclic system in which a four-membered carbocyclic ring bridges the C-1 and C-11 positions of a classical triterpenoid framework. A plausible pathway for the biosynthesis of 1-4 is proposed. Biological studies reveal that 1-4 dose-dependently protect age-related renal fibrosis in vitro .