Abstract: From the roots of Stemona japonica Miq., three stemona alkaloids, didehydrostemonine 1, ste-monine 2 and didehydroprotostemonine 3, were isolated by means of extensive Sil gel chromatographic separation. Their structures were identified by spectral analyses (IR, MS, ¹H, ¹³C NMR, ¹H-¹H COSY, NOESY, HMQC, HMBC) as well as 1H NMR line broadening effect. Compound 1 was a new stemona alkaloid, and 3 was a didehydroazaazu-lene alkaloid occurring in S. tuberosa, discovered in the roots of S. japonica firstly.

Key words: Stemona japonica Miq, Stemona japonica Miq, Didehydrostemonine, Didehydrostemonine, Spectral analysis, Spectral analysis