Abstract:Five limonoids were isolated from the root bark of Dictamnus angustifolius G. Don. Their structures were determined as fraxinellone, obacunone, limonin, limonin diosphenol, and dictamdiol respectively, on the basis of their spectral data and chemical methods. Dictamdiol is a new natural degraded limonoid lactone derivative. Relative stereochemistry was established by two-dimensional correlation spectroscopic (COSY) experiment and biogenesis.