Yasuyuki Nogata

Antifouling activity of synthetic polymer gels against cyprids of the barnacle (Balanus amphitrite) in vitro

Barnacle (Balanus amphitrite) settlement on synthetic hydrogels with various chemical structures was tested in laboratory assays. The results demonstrated that cyprids settle less or not at all on hydrogels and PDMS elastomer compared with the polystyrene control. The low settlement on gels is most likely due to the ‘easy release’ of initially attached cyprids from the gel surfaces. This low adhesion of cyprids is independent of surface hydrophilicity or hydrophobicity, and of surface charge. The results also revealed that hydrogels can be categorized into two groups. One group showed an extremely strong antifouling (AF) performance that was independent of the elasticity (E) or swelling degree (q) of the gels. The second group showed relatively less strong AF performance that was E- or q-dependent. In the latter case, E, rather than the q, may be the more important factor for cyprid settlement.

Antifouling Activity of Simple Synthetic Isocyanides Against Larvae of the Barnacle Balanus amphitrite

Twelve simple linear isocyanides were synthesized and examined for antifouling activity and toxicity against cyprid larvae of the barnacle, Balanus amphitrite. Larval settlement was inhibited, with EC50 values of 0.046 – 1.90 μg ml−1, and they were much less toxic (LD50 values ranging over 21.28 μg ml−1) than CuSO4 (EC50 0.30 μg ml−1 and LD50 2.95 μg ml−1). The data indicate that simple linear isocyanides are promising non-toxic antifouling agents.

Larval development and settlement of a whale barnacle

Larval development and settlement of whale barnacles have not previously been described, unlike intertidal barnacles. Indeed, the mechanisms of the association between barnacles and whales have not been studied. Here we describe the larval development and settlement of the whale barnacle, Coronula diadema, and possible involvement of a cue from the host in inducing larval settlement. Eight-cell stage embryos were collected from C. diadema on a stranded humpback whale, incubated in filtered seawater for 7 days, and nauplius larvae hatched out. When fed with Chaetoceros gracilis, the nauplii developed to stage VI, and finally metamorphosed to the cypris stage. The larval development looked similar to that of intertidal barnacles with planktotrophic larval stages. The cyprids did not settle in normal seawater, but did settle in polystyrene Petri dishes when incubated in seawater with a small piece of skin tissue from the host whale. This strongly suggests the involvement of a chemical cue from the host whale tissue to induce larval settlement.

Synthesis and Anti-barnacle Activities of Novel Isocyanocyclohexane Compounds Containing an Ester or an Ether Functional Group

Ten novel isocyanocyclohexane compounds that possess an oxygenic functional group at the 4-position were synthesized and evaluated for their antifouling activity against the larvae of the barnacle Balanus amphitrite with the aim of exploring the structure – activity relationships further. The anti-barnacle effect of the synthesized compounds was in the EC50 range of 0.0096 – 17.0 μg ml−1. Some ester derivatives exhibited extremely high antifouling activities, and none of the synthesized isocyanocyclohexane compounds showed significant toxicity. The results suggest that the ester function is one of the important groups in the expression of potent antifouling activity in isocyano compounds.

Synthesis and anti-barnacle activities of novel 3-isocyanotheonellin analogues

An antifouling active natural compound, 3-isocyanotheonellin, and its analogues were synthesized and evaluated for antifouling activity against the larvae of the barnacle Balanus amphirite in order to explore structure-activity relationships. The anti-barnacle effect of the 3-isocyanotheonellin analogues was in the EC 50 range 0.18-7.20 w g ml m 1 . Some synthesized analogues exhibited potent antifouling activity as high as 3-isocyanothoenllin, and none of the synthesized isocyano compounds showed significant toxicity. The results of the present study suggest that an isocyano group and a hydrophobic site at a suitable position are important for potent antifouling activity without toxicity.

Omaezallene from Red Alga Laurencia sp.: Structure Elucidation, Total Synthesis, and Antifouling Activity

Natural antifouling products have been the subject of considerable attention. We screened marine algae for antifouling activity and discovered omaezallenes, the new bromoallene-containing natural products isolated from the red alga Laurencia sp. Described is the isolation, structure elucidation, and total syntheses of omaezallenes. The relative and absolute configurations of natural omaezallenes were unambiguously established through total synthesis. The antifouling activities and ecotoxicity of omaezallenes were also evaluated.

Poly-ethers from Winogradskyella poriferorum: Antifouling potential, time-course study of production and natural abundance

A sponge-associated bacterium, Winogradskyella poriferorum strain UST030701-295T was cultured up to 100l for extraction of antifouling bioactive compounds. Five poly-ethers were isolated and partially characterized based on nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS); two of them showed inhibitory effects on biofilm formation of marine bacteria and larval settlement of macro-foulers but did not produce any adverse effects on the phenotypes of zebra fish embryos at a concentration of 5μg ml(-1). The effect of culture duration on the production of the poly-ethers and the bioactivity of the relevant extracts was monitored over a period of 12 days. The total crude poly-ether production increased from day 2 to day 5 and the highest bioactivity was observed on day 3. The poly-ethers were found to be localized in the cellular fraction of the extracts, implying their natural occurrence. The potent bioactivity of these poly-ethers together with their high natural abundance in bacteria makes them promising candidates as ingredients in antifouling applications.

Koshikamide A1, a new cytotoxic linear peptide isolated from a marine sponge Theonella sp

Abstract Koshikamide A1, a new cytotoxic linear peptide, was isolated from a marine sponge, Theonella sp. Its structure was elucidated by spectroscopic and chemical methods.

Wewakazole B, a Cytotoxic Cyanobactin from the Cyanobacterium Moorea producens Collected in the Red Sea.

A mass spectrometry (MS)-guided isolation has led to the purification of a new cyanobactin, wewakazole B (1), along with the known compound curacin D from a Red Sea Moorea producens. The planar structure of 1 was elucidated using a combination of NMR and MS techniques. After ozonolysis and acid hydrolysis, the absolute configurations of the amino acid components of 1 were determined by chiral-phase LC-MS and HPLC analyses. Notably, compound 1 exhibited cytotoxic activity toward human MCF7 breast cancer cells (IC50 = 0.58 μM) and human H460 lung cancer cells (IC50 = 1.0 μM) and was also found to be inactive in a siderophore assay.

Purification and partial amino acid sequence analysis of the larval settlement-inducing pheromone from adult extracts of the barnacle, Balanus amphitrite (=Amphibalanus amphitrite)

A previously undescribed larval settlement-inducing protein was purified from adult extracts of the barnacle, Balanus amphitrite (=Amphibalanus amphitrite). Results of SDS-PAGE indicated that the relative molecular mass of the protein in reduced and denatured form is 31,600 ± 500 kDa, and that it is distinct from the Settlement Inducing Protein Complex (SIPC) which has previously been determined as a larval settlement-inducing pheromone. The N-terminal 33-residue sequence of the intact protein showed no similarity with previously reported proteins in the EMBL/Genbank/DDBJ databases. The purified protein at a concentration of 10 μg ml−1 induced approximately four times more larval settlement than the control (filtered natural seawater). In addition, results of the assay using both 24-well polystyrene plates and agarose gels indicated that this protein is probably released into seawater and attracts cypris larvae. These results suggest that the purified protein is a waterborne type pheromone which induces settlement of larvae of B. amphitrite.