Publications by authors named "Takaaki Kubota"

Objectives: The bacterium Porphyromonas gingivalis is a major causative agent of periodontitis. In this study, the anti-P. gingivalis compound in bilberry (Vaccinium myrtillus L.

View Article and Find Full Text PDF

A new psammaplysin derivative, ceratinadin G (), was obtained from the Okinawan marine sponge sp., and the gross structure was clarified through spectroscopic and spectrometric analyses. The absolute configuration of compound was established by comparing its NMR and ECD data with those of the known psammaplysin derivative, psammaplysin F ().

View Article and Find Full Text PDF

Despite the recent progress in public health measures, malaria remains a troublesome disease that needs to be eradicated. It is essential to develop new antimalarial medications that are reliable and secure. This report evaluated the pharmacokinetics and antimalarial activity of 1,2,6,7-tetraoxaspiro[7.

View Article and Find Full Text PDF

Zamamiphidins B () and C (), two new manzamine-related alkaloids with an unprecedented fused diazahexacyclic ring system, were isolated from an sp. marine sponge collected in Okinawa. The structures of zamamiphidins B () and C () including the relative configurations were elucidated on the basis of spectroscopic data.

View Article and Find Full Text PDF
Article Synopsis
  • Dinoflagellates, such as Amphidinium gibbosum, can cause harmful algal blooms by releasing toxic compounds, but understanding their toxin production has been difficult due to their large genomes.
  • Researchers sequenced the genome of A. gibbosum and used an integrated omics approach to identify how nutrient availability affects the biosynthesis of secondary metabolites, revealing key genetic elements like non-ribosomal peptide synthetase.
  • The findings highlight complex regulatory mechanisms in dinoflagellate metabolism, including post-transcriptional control by microRNAs and alternative splicing, contributing to our understanding of toxin production and dinoflagellate evolution.
View Article and Find Full Text PDF

The production and accumulation of advanced glycation end products (AGEs) have been implicated in diabetes and diabetic complication. This study was conducted as a search for an AGE inhibitor from brown alga, Sargassum macrocarpum. Separation and purification were performed using AGEs inhibitory activity as an index, yielding isolation of 11 meroterpenoids, of which 3 were new compounds: macrocarquinoids A (1), B (6), and C (9).

View Article and Find Full Text PDF

Two new polyacetylene glycosides, kamiohnoyneosides A and B, were isolated from the flowers of edible Chrysanthemum "Kamiohno", along with a known polyacetylene glycoside and two known monoterpene glycosides. The structures of new compounds were elucidated on the basis of spectroscopic data. Kamiohnoyneoside A and three known compounds moderately inhibited formation of N-(carboxymethyl)lysine, one of the representative advanced glycation endproducts.

View Article and Find Full Text PDF

The manzamine alkaloids are absolutely one of the most fascinating marine natural products. The representative manzamine alkaloids, manzamines A-C, were isolated from a marine sponge Haliclona sp. collected off Cape Manzamo, Okinawa, Japan.

View Article and Find Full Text PDF

Two new bromotyrosine alkaloids, ma'edamines C and D, were isolated from an Okinawan marine sponge sp. The structures of ma'edamines C and D were elucidated on the basis of spectroscopic data. Ma'edamines C and D were the first natural products possessing a unique tetrasubstituted pyridinium moiety such as -alkyl-3,5-diethyl-2-propylpyridinium and -alkyl-3,5-diethyl-4-propylpyridinium, respectively.

View Article and Find Full Text PDF

Two new bromotyrosine alkaloids, ceratinadins E () and F (), were isolated from an Okinawan marine sponge sp. as well as a known bromotyrosine alkaloid, psammaplysin F (). The gross structures of and were elucidated on the basis of spectroscopic data.

View Article and Find Full Text PDF

The investigation of the Vietnamese marine sponge Spongia sp. led to the isolation of three new sesquiterpene phenols, langconols A-C (1-3), and one new sesquiterpene hydroxyquinone, langcoquinone C (4), together with two known meroterpenoids (5 and 6). Their structures were determined on the basis of spectroscopic analyses and comparisons with published data.

View Article and Find Full Text PDF

A new manzamine alkaloid, zamamidine D (1), was isolated from an Okinawan Amphimedon sp. marine sponge. The structure of zamamidine D (1) including the relative configuration was elucidated on the basis of spectroscopic data.

View Article and Find Full Text PDF

The biogenetic origins of amphidinin A (1) and amphidinolide P (2) were investigated by feeding experiments with (13)C-labeled acetates. (13)C-NMR data of (13)C-enriched samples revealed that the all carbons of 1 and 2 were derived from acetates. The polyketide chain of 1 was formed from one triketide chain, two diketide chains, and three unusual isolated C1 units derived from C-2 of cleaved acetates, while the polyketide chain of 2 was formed from one pentaketide chain, two acetate units, and three unusual isolated C1 units derived from C-2 of cleaved acetates.

View Article and Find Full Text PDF

New bisindole alkaloids, hyrtinadines C (1) and D (2), have been isolated from an Okinawan marine sponge Hyrtios sp. The structures of hyrtinadines C (1) and D (2) were elucidated based on analyses of the spectral data. Hyrtinadines C (1) and D (2) were the relatively rare alkaloids possessing a 3,4-fused azepinoindole skeleton.

View Article and Find Full Text PDF

Microorganisms that utilize various D-amino acids (DAAs) were successfully isolated from deep-sea sediments. The isolates were phylogenetically assigned to Alphaproteobacteria, Gammmaproteobacteria, and Bacilli. Some of the isolates exhibited high enantioselective degradation activities to various DAAs.

View Article and Find Full Text PDF

The total synthesis of 7,10-epimer of the proposed structure of amphidinolide N was accomplished. The requisite chiral C17-C29 subunit was assembled stereoselectively via Keck allylation, Shi epoxidation, diastereoselective 1,3-reduction, and a later oxidative synthesis of the THF framework. The C1-C13 and C17-C29 subunits were successfully coupled using a Enders RAMP "linchpin" as the C14-C16 three carbon unit, thereby controlling the chirality at C14 and C16.

View Article and Find Full Text PDF

Amphidinolide N, the structure of which has been recently revised, is a 26-membered macrolide featuring allyl epoxide and tetrahydropyran moieties with 13 chiral centers. Due to its challenging structure and extraordinary potent cytotoxicity, amphidinolide N is a highly attractive target of total synthesis. During our total synthesis studies of the 7,10-epimer of the proposed structure of amphidinolide N, we have synthesized the C1-C13 subunit enantio- and diastereoselectively.

View Article and Find Full Text PDF

A novel, anaerobic bacterium, strain MO-SEDI, was isolated from a methanogenic microbial community, which was originally obtained from marine subsurface sediments collected from off the Shimokita Peninsula of Japan. Cells were Gram-stain-negative, non-motile, non-spore-forming rods, 0.4-1.

View Article and Find Full Text PDF

Two distinct bacterial and eukaryotic serine racemases (SRs) have been identified based on phylogenetic and biochemical characteristics. Although some reports have suggested that marine heterotrophic bacteria have the potential to produce d-serine, the gene encoding bacterial SRs is not found in those bacterial genomes. In this study, using in-depth genomic analysis, we found that eukaryotic SR homologues were distributed widely in various bacterial genomes.

View Article and Find Full Text PDF

Two new bromotyrosine alkaloids, tyrokeradines G (1) and H (2), have been isolated from an Okinawan marine sponge of the order Verongida. The structures of 1 and 2 were elucidated on the basis of spectroscopic data. Tyrokeradine G (1) is the first bromotyrosine alkaloid possessing a β-alanine unit, while tyrokeradine H (2) is a rare bromotyrosine alkaloid possessing a N-substituted pyridinium ring.

View Article and Find Full Text PDF

A β-1,3-glucanase (LpGluA) of deep subseafloor Laceyella putida JAM FM3001 was purified to homogeneity from culture broth. The molecular mass of the enzyme was around 36 kDa as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). LpGluA hydrolyzed curdlan optimally at pH 4.

View Article and Find Full Text PDF

Speradine A is a derivative of cyclopiazonic acid (CPA) found in culture of an Aspergillus tamarii isolate. Heterologous expression of a predicted methyltransferase gene, cpaM, in the cpa biosynthesis gene cluster of A. tamarii resulted in the speradine A production in a 2-oxoCPA producing A.

View Article and Find Full Text PDF

Iejimalides (IEJLs) A-D are 24-membered macrolides isolated from a tunicate Eudistoma cf. rigida, and exhibit potent cytotoxicity in vitro and antitumor activity in vivo. We previously reported that the molecular target of IEJL-A and -B was the vacuolar-type H(+)-ATPases (V-ATPases).

View Article and Find Full Text PDF

Four new polyketides, amphidinins C-F (1-4), have been isolated from the culture broth of symbiotic dinoflagellate Amphidinium sp. The analysis of their spectral data revealed that amphidinins C-F (1-4) were 4,5-seco-analogues of amphidinolide Q (5). The absolute configurations of the new compounds were elucidated by the combination of J-based configuration analysis, modified Mosher's method, and chemical derivatization.

View Article and Find Full Text PDF