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Phytochemical investigation of the shells of Metaplexis japonica (Thunb.) Makino, belonging to the family of Apocynaceae, afforded three new pregnane steroids, metajapogenins A–C, along with three known compounds. The structures of the new compounds were elucidated as 12β,14β,17β-trihydroxypregna-3,5-dien-7,20-dione, 12β,14β,17β,20β-tetrahydroxypregna-3,5-dien-7-one; 3β,12β,14β,17β-tetrahydroxypregn-5-ene-7,20-dione on the basis of extensive spectroscopic evidence derived from 1D; 2D-NMR experiments and mass spectrometry. The known compounds included pergularin; 12-O-acetylpergularin; and pergularin-3-O-β-d-oleandropyranose; which were identified for the first time in the shells of M. japonica.