Two new sesquiterpenes (1–2) and three new nor-sesquiterpenes (3–5) were obtained from the rhizome of Alisma orientale (Sam.) Juzep, one of which (2) possessed an unprecedented cyclopentene and furanone containing natural skeleton. Their structures and relative stereochemistry were elucidated by NMR spectroscopy (1H and 13C NMR, HSQC, HMBC, NOESY) and electronic circular dichroism (ECD) and HR-ESI-MS data analyses. Two plausible biosynthetic pathways for compound 1 and 2 were discussed. The nephrotoxicities of these compounds were evaluated on normal human HK2 cells by high content screening, and neither the MeOH extract nor the compounds possessed potential nephrotoxicity in vitro.
