title: Antifouling diketopiperazines produced by a deep-sea bacterium, Streptomyces fungicidicus.
abstract: Modern antifouling coatings use heavy metals and toxic organic molecules to prevent biofouling, the undesirable growth of marine organisms on man-made substrata. In an ongoing survey of deep-sea microorganisms aimed at finding low toxic antifouling metabolites, an actinomycete bacterium was isolated from the Pacific sediment at the depth of about 5000 m. The bacterium was closely related to Streptomyces fungicidicus (99% similarity) according to 16S ribosomal RNA sequence information. The spent culture medium of this bacterium inhibited barnacle larval attachment. Bioassay-guided fractionation was employed to isolate antifouling compounds. The ethyl acetate extract was fractionated by using an open silica gel column. Active fractions were further purified on a HPLC C18 column. Five diketopiperazines, cyclo-(L-Leu-L-Pro), cyclo-(L-Phe-L-Pro), cyclo-(L-Val-L-Pro), cyclo-(L-Trp-L-Pro), and cyclo-(L-Leu-L-Val) were isolated for the first time from a deep sea bacterium, and the structures of the compounds were elucidated by nuclear magnetic resonance spectroscopy and mass spectrometry. The pure diketopiperazines were tested for antilarval activity using the barnacle Balanus amphitrite. Effective concentrations that inhibited 50% larval attachment (EC50) after 24 h ranged from 0.10- 0.27 mM. The data suggest that diketopiperazines and other compounds from deep-sea bacteria may be used as novel antifoulants.
authors.affiliation: Department of Biology/Coastal Marine Laboratory, Hong Kong University of Science & Technology (HKUST), Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Xiancui
authors.initials: X
authors.lastname: Li
authors.forename: Sergey
authors.initials: S
authors.lastname: Dobretsov
authors.forename: Ying
authors.initials: Y
authors.lastname: Xu
authors.forename: Xiang
authors.initials: X
authors.lastname: Xiao
authors.forename: Oi Shing
authors.initials: OS
authors.lastname: Hung
authors.forename: Pei-Yuan
authors.initials: PY
authors.lastname: Qian
mesh_terms: D000818:Animals; D054659:Diketopiperazines; D007814:Larva / Q000187:drug effects; D015394:Molecular Structure; D009792:Oceans and Seas; D010456:Peptides, Cyclic / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D010879:Piperazines / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology*; D013302:Streptomyces / Q000378:metabolism*; D001468:Thoracica / Q000187:drug effects* / Q000254:growth & development
chemical_list: D054659:Diketopiperazines; D010456:Peptides, Cyclic; D010879:Piperazines