From the root bark of Dictamnus dasycarpus (Rutaceae), four limonoid derivatives, two furoquinoline alkaloids, five limonoids, two sesquiterpenes and three steroids were isolated and their structures elucidated on the basis of various spectroscopic methods. Among the identified compounds, one was determined to be a new natural product, 6 beta-hydroxyfraxinellone, while six compounds were found to be active against the plant pathogenic fungus Cladosporium cucumerinum. The relationship between the structures of limonoid derivatives and their inhibitory activity against fungal growth was investigated.