The non-cyclized possible biogenetic precursors of girinimbine and mahanimbine, 2-hydroxyl-3-methyl-1-(3-methyl-2-butenyl)carbazole (girinimbilol) and 2-hydroxyl-3-methyl-1-(3,7-dimethyl-2,6-octadienyl)carbazole (mahanimbilol) have been isolated from the stem bark of Murraya koenigii. The structures were established by cyclization to dihydrogirinimbine and a new bicyclocarbazole, bicyclomahanimbiline, respectively.