Identification and biosynthetic origins of sterols in the marine bryozoan Bugula neritina

The sterols of Bugula neritina have been isolated and characterized spectroscopically. Cholesterol was found to be the predominant sterol with C-28, C-29, and C-30 sterols recovered as minor components. In vivo biosynthetic experiments revealed that cholesterol is the only sterol produced by de novo biosynthesis, indicating that the other sterols are of dietary origin. Further, biosynthetic experiments using in vitro techniques indicated that 24-alkylated sterols (4, 5, 7, and 8) are produced by alkylation of dietary sterols, while others are exclusively of dietary origin.