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Abstract: Azaspiracid-2 was isolated from a marine sponge Echinoclathria sp. collected off Amami-Oshima as the predominant cytotoxic constituent. A combination of HPLC using ODS, GS320, and Phenylhexyl stationary phases permitted the purification without using acid or inorganic additives in the mobile phase. Azaspiracid-2 exhibited potent cytotoxicity against P388 cells with an IC50 value of 0.72ng/mL and caused S phase arrest on the cell cycle. [Copyright &y& Elsevier]

New 34-membered polyol macrolides JBIR-129 (1) and JBIR-139 (2) were isolated from the culture of the terrestrial Streptomyces RK74. The planar structures of 1 and 2 were established on the basis of 1D and 2D NMR, ESI-TOF-MS, IR, and UV spectra. The relative configurations of the sugar units were determined by analyzing vicinal ¹H-¹H coupling constants and steric information. Both 1 and 2 showed cytotoxic activity against human ovarian adenocarcinoma SKOV-3 cells with IC₅₀ values of 0.3 and 0.4 μM, respectively.

Three new trichostatin analogues, JBIR-109 (1), JBIR-110 (2), and JBIR-111 (3), were isolated from the culture of the marine sponge-derived Streptomyces sp. strain RM72, together with trichostatin A (4) and trichostatic acid (5). The planar structures of 1-3 were determined on the basis of extensive NMR and MS analyses. In addition, the absolute configurations of the amino acid residues were determined by Marfey's method. The histone deacetylase inhibitory activities of 1-5 were examined, and their structure-activity relationships are discussed.

The search for metabolites of Kibdelosporangium sp. AK-AA56 resulted in the discovery of novel N-phenylacetylated peptides, JBIR-78 (1) and JBIR-95 (2). Compounds 1 and 2 were established to be N-phenylacetylated heptapeptides by extensive NMR and HRESIMS analyses. The absolute configuration of the standard amino acids including a cysteic acid moiety was determined using Marfey's method on the acid hydrolysates of 1 and 2. The relative and absolute configurations of a nonstandard amino acid, β-hydroxyleucine, were elucidated using the J-based and modified Mosher's methods, respectively. In an antimicrobial test, 1 showed antibacterial activity against Micrococcus luteus.

Searching for metabolites from Streptomyces sp. RI051-SDHV6 resulted in the discovery of a novel peptide, JBIR-96 (1). The structure of 1 was established as an N-phenylacetylated pentapeptide involving a cysteic acid and a peptide lactone structure by extensive NMR and MS analyses. In addition, the absolute configuration of 1 was established by Marfey's and modified Mosher's methods.

During the course of our screening program to isolate isoprenoids from marine Actinobacteria, 523 actinobacterial strains were isolated from 18 marine sponges, a tunicate, and two marine sediments. These strains belonged to 21 different genera, but most were members of Streptomyces, Nocardia, Rhodococcus, and Micromonospora. Some Actinobacteria have been reported to use the mevalonate pathway for the production of isoprenoids as secondary metabolites. Therefore, we investigated whether these strains possessed the 3-hydroxyl-3-methylglutaryl coenzyme A reductase (hmgr) gene, which indicates the presence of the mevalonate pathway. As a result, six strains belonging to the genera Streptomyces (SpC080624SC-11, SpA080624GE-02, and Sp080513GE-23), Nocardia (Sp080513SC-18), and Micromonospora (Se080624GE-07 and SpC080624GE-05) were found to possess the hmgr gene, and these genes were highly similar to hmgr genes in isoprenoid biosynthetic gene clusters. Among the six strains, the two strains SpC080624SC-11 and SpA080624GE-02 produced the novel isoprenoids, JBIR-46, -47, and -48, which consisted of phenazine chromophores, and Sp080513GE-23 produced a known isoprenoid, fumaquinone. Furthermore, these compounds showed cytotoxic activity against human acute myelogenous leukemia HL-60 cells.

Two new aminocaprophenone alkaloids, ficuseptamines A (1) and B (2), and a new pyrrolidine alkaloid, ficuseptamine C (3), together with 12 known alkaloids and a known acetophenone derivative were isolated from a methanolic extract of the leaves of Ficus septica. The structures of 1-3 were determined on the basis of their spectroscopic data. The compounds obtained were evaluated for cytotoxicity against two cancer cell lines.

A Gram-positive-staining, facultatively anaerobic bacterial strain, CTT-37T, was isolated from a marine sediment sample collected from Tottori city, located on the shore of the Sea of Japan. A 16S rRNA gene sequence comparison indicated that the isolate represents a novel clade that clusters with members of the families Cellulomonadaceae and Sanguibacteraceae. Strain CTT-37T shared maximum 16S rRNA gene sequence similarity of 96.4% with Oerskovia paurometabola DSM 14281T and 96.2% with Oerskovia enterophila DSM 43852T. The DNA-DNA hybridization value between strain CTT-37T and O. enterophila JCM 7350T was 10-12%. The following chemotaxonomic characteristics of strain CTT-37T were markedly different from those of strains in the genus Oerskovia. The cell wall contained L-serine in the peptidoglycan interpeptide bridge. The predominant menaquinone was MK-9 (H4); other quinones detected were MK-9 and MK-9(H2). The only polar lipid was phosphatidylglycerol and the G+C content of the DNA was 70 mol%. Differences in phenotypic characteristics and large phylogenetic distances between strain CTT-37T and all members of the genus Oerskovia supported the classification of CTT-37T within a new genus and species, for which the name Paraoerskovia marina gen. nov., sp. nov. is proposed. The type strain of Paraoerskovia marina is CTT-37T (=NBRC 104352T=DSM 21750T).