Twenty isoquinoline alkaloids were identified in the aerial part of Fumaria densiflora DC. In addition to bicuculline, densiflorine, fumaritine, fumariline, scoulerine, coptisine, cryptopine, parfumine, protopine, and sinactine which have been found previously, the following alkaloids were isolated for the first time from this species: adlumine, fumaricine, fumaritridine, fumarophycine, fumarofine, corytuberine, cis-N-methylstylopinium iodide, stylopine, and two new 1-benzylisoquinoline alkaloids, viz. fumaflorine and fumaflorine methyl ester. The cytoprotectivity of extracts of F. densiflora and F. officinalis, and that of protopine, cryptopine, and parfumine was tested on primary cultures of rat hepatocytes intoxicated with carbon tetrachloride. The cytoprotective effect of the extracts is associated with the alkaloids.