The alkaloid composition of the seeds and roots of the plant Haplophyllum perforatum growing in Tadzhikistan (Karateg range) has been studied for the first time. In addition to the known furoquinoline alkaloids, the new alkaloid haplosine has been isolated and it has been shown to be identical with the product of the hydrogenolysis of haplopine. Among natural compounds, this is the first representative of derivatives of the 3-ethyl-4-methoxy-quinolin-2-one series. © 1992 Plenum Publishing Corporation.