ACICULITINS A-C - CYTOTOXIC AND ANTIFUNGAL CYCLIC-PEPTIDES FROM THE LITHISTID SPONGE ACICULITES ORIENTALIS

The lithistid sponge Aciculites orientalis contains three cyclic pepti des, aciculitins A-C (1-3), that are identical except for homologous l ipid residues. The structure of the major peptide, aciculitin B (2), w as elucidated by interpretation of spectroscopic data. The aciculitins consist of a bicyclic peptide that contains an unusual histidino-tyro sine bridge. Attached to the bicyclic peptide are C-13-C-15 2,3-dihydr oxy-4,6-dienoic acids bearing D-lyxose at the 3-position. The structur es of aciculitamides A (4) and B (5), which are artifacts obtained ear lier from this sponge, are also presented. The aciculitins 1--3 inhibi ted the growth of Candida albicans and were cytotoxic toward the HCT-1 16 cell line.