From cell cultures of Eschscholtzia californica and their spent medium, three new benzo[c]phenanthridine alkaloids--namely 10-hydroxysanguinarine [2a], 12-hydroxychelirubine [4a], and 10-hydroxychelerythrine [7a]--and two new dihydrobenzo[c]phenanthridine alkaloids--10-hydroxydihydrosanguinarine [2b] and 12-hydroxydihydrochelirubine [4b]--together with the known constituents sanguinarine [1a], chelirubine [3a], macarpine [5a], dihydrosanguinarine [1b], dihydrochelirubine [3b], and dihydromacarpine [5b], were isolated and characterized. Structure elucidations were done by 1H nmr, decoupling experiments, and NOESY spectra. Isolated microsomes from E. californica, the site of hydroxylation activity within the cells, contained the whole set 1b to 8b of 5,6-dihydrobenzo[c]phenanthridines. A scheme for the biosynthesis of macarpine [5a] from protopine [9] via dihydrosanguinarine [1b] is presented.