title: Halocyamines: novel antimicrobial tetrapeptide-like substances isolated from the hemocytes of the solitary ascidian Halocynthia roretzi.
abstract: Two novel antimicrobial tetrapeptide-like substances, halocyamine A and B, were isolated from the solitary ascidian Halocynthia roretzi by a procedure including extraction steps, chromatographies on coarse and fine HP-20 columns, and preparative reversed-phase high-performance liquid chromatography. The structures of halocyamine A and B were determined to be L-histidyl-L-6,7-dihydroxyphenylalanylglycyl-6-bromo-8,9-didehy drotryptamine and L-threonyl-L-6,7-dihydroxyphenylalanyl-L-histidyl-6-bromo-8,9- didehydrotryptamine, respectively, by spectral analyses and degradation studies. Besides antimicrobial activities against several kinds of bacteria and yeasts, both of them showed cytotoxic activities against neuronal cells cultured from rat fetal brain, mouse neuroblastoma N-18 cells, and human hepatoma Hep-G2 cells. They were only detected in the "morula"-like cells, which are of the most abundant cell type among the hemocytes of H. roretzi.
authors.affiliation: Department of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Azumi
authors.forename: H
authors.initials: H
authors.lastname: Yokosawa
authors.forename: S
authors.initials: S
authors.lastname: Ishii
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000302:isolation & purification*; D055598:Chemical Phenomena; D002621:Chemistry; D002816:Chordata, Nonvertebrate / Q000032:analysis; D006434:Hemocytes / Q000032:analysis; D008826:Microbial Sensitivity Tests; D015394:Molecular Structure; D009842:Oligopeptides / Q000302:isolation & purification* / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D009842:Oligopeptides; C063392:halocyamine A; C063393:halocyamine B