Alisma plantago-aquatica Linn. Thunb. (Alismaceae) is widely distributed in the marshes in Fujian province of China. It has long been used in traditional medicine for the treatment with oliguria, edema, diarrhea, nephropathy, dizziness and hyperlipidemia, diabetes, atherosclerotic, and inflammation. Previous phytochemical studies have reported the isolation of protostane-type triterpenoids, phenylpropanoid amides, and sesquiterpenes. Among them, protostane-type triterpenoids are considered to be the main bioactive components for purgative diarrhea. Herein, we report the isolation and structural elucidation of twenty undescribed protostane-type triterpenoids (1-15), which can be divided into different structur al types : 17-spirost protostane-typy, nor-protostanes-typy, carbonylation derivatives of alisol A and alisol B type , and dehydroxylation derivatives of alisol A and alisol B type. The structures of new compounds are elucidated by 1D-, and 2D-NMR techniques including HSQC, HMBC, 1H–1H COSY and NOESY spectra. Based on these, we summarize characteristic NMR signals of those compounds for the rapid identification of protostane-type . All isolates were evaluated for their inhibitory effects on LPS-induced NO production in Caco-2 cells.