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Research

Our laboratory conducts research in environmental earth science using marine natural products chemistry and chemical ecology as foundation.

Due to changes in the global environment, our ecosystems are also changing significantly. Although this change can be attributed to numerous factors, our laboratory focuses on investigating the impact of various chemicals on the environment. With respect to the substances associated with biological interactions among marine invertebrates, algae, and microorganisms, we conduct research studies using natural product chemistry as a starting point.

In addition, we also perform exploratory research investigations on bioactive substances present in cyanobacteria and marine organisms as part of the above-mentioned research.

For these research projects, we have been aggressively developing organism- and cell-based assays as well as enzyme-based biochemical tests to integrate these developments into chemical research.

We are expanding our research fields from the isolation of bioactive substances, determination of their structures through instrumental analysis, and evaluation of their bioactivities to biosynthesis research at the gene level.


We are specifically working on the following research themes:


1. Seaweed-derived anti-fouling substances

To prevent the attachment of periphyton such as barnacles, an anti-fouling paint is applied to the hull of ships. Commonly used organotin compounds and some of the recently introduced alternative paints are subject to regulation due to their toxicity. In collaboration with the private sector, we are currently working on the development and practical application of an anti-fouling substance derived from a marine invertebrate as a lead compound. We are seeking novel anti-fouling substances that are effective against seaweeds, cyanobacteria, and the cypris-form larvae of striped barnacles. Regarding the anti-fouling substances obtained, we are currently investigating the expression mechanisms underlying the toxic activity of substances whose ecotoxicities are extremely low. Details of our biosynthesis research using these substances are described in the next section.

 

2. Biosynthesis research on halogen-containing compounds derived from seaweeds

As described in the previous section, the anti-fouling substances obtained from seaweeds contain halogens such as bromine. This property of producing halogen-containing compounds is a major characteristic of marine organisms. Research has shown that some halogen-containing compounds have anti-fouling activity, as well as antitumor effects that maybe used as antitumor drugs. Therefore, to elucidate the biosynthesis mechanisms of halogen-containing compounds, we conduct research studies focusing on vanadium-dependent bromoperoxidase present in Laurencia (red alga).

 

3. Enzyme inhibitory substances produced by cyanobacteria

We have previously shown that cyanobacteria produce various peptides with enzyme inhibitory activity. Attempts to purify these peptides have been difficult; however, we will continue to perform these experiments because these compounds may be potentially used as pharmaceutical drugs. We are also interested in the relationship between the ecology of water blooms, which occur on a large-scale in eutrophic lakes, and the secondary metabolites of cyanobacteria. We have recently been collecting marine cyanobacteria overseas to isolate new bioactive substances. Our cyanobacterial peptide research projects are mainly based on the use of liquid chromatography–mass spectrometry (LC/MS) equipment such as micrOTOF and Orbitrap (university equipment managed by us).

 

4. Chemical factors that determine the spawning environment of eels

We have recently reached a milestone in our research on the spawning environment of the Japanese eel by identifying its spawning area. As a next step, we will identify chemical factors that determine the spawning environment of this organism.


5. Substances that induce transformation in echinoderms

We have been screening seaweeds and their surrounding seawater for substances that induce the transformation of sea urchins and sea cucumbers from larvae to young adults. In collaboration with the National Center for Stock Enhancement, Japan, we have been conducting experiments using echinoderm larvae. Our studies have shown that dopamine induces the transformation of sea cucumbers, and we are currently investigating dopamine receptors in these organisms.

 

6. Chlorosulfolipids

Ochromonas danica (Chrysophyta) is known to contain a large amount of chlorosulfolipids, which are compounds that contain chloride and sulfate groups. Although stereochemical analysis has not been carried out on these compounds in the last 40 years, our successful isolation of
chlorosulfolipids has led to the identification of their steric configuration. Academic interest in chlorosulfolipids, including their synthesis, has rapidly grown in recent years. We are also conducting mass spectrometry (MS) analysis of these compounds.

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