Abstract: Eight alkaloids had been isolated from the roots of Stephania rnacrantha H. S. Lo et M. Yang which is a novel species growing in Yang-bi district of Yunnan Province. The structures of these compounds were identified as l-tetrahydropalmatine ( Ⅰ ), isocorydine ( Ⅱ ), corydine ( Ⅲ ), corydalmine (Ⅳ), stepholidine ( Ⅴ ), palmatine ( Ⅵ ), corytuberine salt (Ⅶ) and laudanidine (Ⅷ) by means of spectral and chemical methods. Isocorydine is a main alkaloid with 1.82% yield. It is interested that laudanidine is found for the first time in the plants of Menispermaceae.

Key words: Stephania macrantha, l-tetrahYdropalmatine, Isocorydine, Laudanidine