Satoshi Miyanaga

Lupinacidin C, an Inhibitor of Tumor Cell Invasion from Micromonospora lupini

A new anthraquinone derivative, lupinacidin C (1), was isolated from the endophytic actinomycete Micromonospora lupini. The structure was elucidated on the basis of spectroscopic analyses, and the absolute configuration was determined by total synthesis. Lupinacidin C (1) exhibited the most potent inhibitory effects among the congeners on the invasion of murine colon carcinoma cells into the reconstituted basement membrane.

Abyssomicin I, a Modified Polycyclic Polyketide from Streptomyces sp. CHI39

Abyssomicin I (1), a new modified polycyclic polyketide, was isolated from the culture extract of a soil-derived Streptomyces sp. The structure of 1 was elucidated by interpretation of NMR and other spectroscopic data. The stereochemistry of the new compound was assigned by NOE analysis, chemical derivatization, and application of the modified Mosher method. While 1 was inactive against bacteria and yeasts, the oxidized derivative 7 showed weak activities against gram-positive bacteria. Compounds 1 and 7 exhibited inhibitory effects on tumor cell invasion with IC(50) values of 11 and 0.21 μM, respectively.

Brartemicin, an inhibitor of tumor cell invasion from the actinomycete Nonomuraea sp.

Brartemicin (1), a new trehalose-derived metabolite, was isolated from the culture broth of the actinomycete of the genus Nonomuraea. Its structure and absolute configuration were determined by spectroscopic analyses. The new compound inhibited the invasion of murine colon carcinoma 26-L5 cells with an IC(50) value of 0.39 microM in a concentration-dependent manner without showing cytotoxic effects.

Revision of the Structure Assigned to the Antibiotic BU-4664L from Micromonopora

The structure assigned to the antitumor antibiotic BU-4664L from Micromonospora sp. was revised to 5,10-dihydro-4,6,8-trihydroxy-10-(3,7,11-trimethyl-trans-2,trans-6,10-dodecatrienyl)-11H-dibenzo[b,e][1,4]-diazepin-11-one based on the NMR analysis.

Absolute Configuration and Antitumor Activity of Myxochelin A Produced by Nonomuraea pusilla TP-A0861 †

In the screening of antitumor compounds from microbial secondary metabolites, myxochelin A was isolated from a culture broth of Nonomuraea pusilla TP-A0861. The absolute configuration was determined to be S by synthesizing both enantiomers from an L- or D-lysine derivative and comparing their specific rotations. Both enantiomers of myxochelin A showed remarkable inhibitory effects on the invasion of murine colon 26-L5 carcinoma cells at non-cytotoxic concentrations.

Rakicidin D, an inhibitor of tumor cell invasion from marine-derived Streptomyces sp.

Tumor metastasis is the leading cause of death in cancer patients. It is the process by which a tumor cell leaves the primary tumor, disseminates to a distant site through the circulatory system and establishes a secondary tumor.1 During the metastatic cascade, tumor cells must pass through the extracellular matrix barriers to accomplish the metastasis. Although the genetic basis of tumorigenesis can vary greatly, the steps required for metastasis are similar for all tumor cells. Therefore, interruption of metastasis is a promising approach to the treatment of cancers of various genetic origins. In our continuing search for anti-invasive compounds from microbial secondary metabolites,2–5 rakicidin D (1) was isolated from the culture broth of an actinomycete strain of the genus Streptomyces. Rakicidins are the 15-membered depsipeptides consisting of three amino acids and a 3-hydroxyfatty acid (Figure 1). To date, three congeners, rakicidins A (2) and B (3) from Micromonospora and rakicidin C (4) from Streptomyces, have been reported.6,7 Rakicidins contain a rare unusual amino acid, 4-amino-2,4-pentadienoate, which has been found only in the secondary metabolites from actinomycetes. Except for rakicidins, only two classes of cyclic peptides, BE435478 and vinylamycin,9 are reported to date to contain this unusual amino acid. Herein, we describe the isolation, structure elucidation and biological properties of rakicidin D (1). The producing strain Streptomyces sp. MWW064 was isolated from a marine sediment sample collected in Samut Sakhon province, Thailand. The strain was cultured in our standard medium for actinomycetes and the whole culture broth was extracted with 1-butanol. The extract showed inhibitory activity toward tumor cell invasion into Matrigel, the reconstituted extracellular matrix proteins.10 Bioassay-guided fractionation of the extract led to the isolation of a new compound, rakicidin D (1). Compound 1 was obtained as a colorless amorphous powder. The high-resolution ESITOFMS indicated a molecular formula of C24H38N4O7, which was consistent with the 1H and 13C NMR data. The IR spectrum of 1 indicated the presence of OH or NH (3356 cm 1) and carbonyl (1688 and 1648 cm 1) functionalities. The UV spectrum and the 1H and 13C NMR spectra of 1 showed high similarity to those for rakicidins A and B.7 The 13C NMR and HMQC analysis confirmed the presence of 24 carbons attributable to six deshielded signals including carbonyl carbons, two sp2 methines, one sp2 methylene, five sp3 methines, six sp3 methylenes, four methyl carbons and five exchangeable protons. 2-Amino-2,4-pentadienoate moiety was elucidated by a COSY correlation for H-9/H-10 and a series of HMBC correlations from H-12 to C-10 and C-11, from H-10 to C-8, C-11 and C-12, and from H-9 to C-8 and C-10 (Figure 2). An NOE between H-10 and an exomethylene proton at dH 5.41 indicated that the latter proton and C-10 were located on the same side of the C-11/C-12 double bond. E configuration for the double bond between C-9 and C-10 was confirmed by a large coupling constant for H-9 and H-10 (JHH1⁄415.0 Hz). HMBC correlations from H-7 to C-6 and C-8, and from H-6 to C-5 and C-8 established the connectivity of N-methylglycine and the pentadienoate. COSY correlations for 2-NH/H-2/H-3 and HMBC correlations from H-2 to C-1, H-3 to C-4 and 4-NH2 to C-3 confirmed the presence of a b-hydroxyasparagine moiety. Connection of this amino acid to the glycine moiety was established by an HMBC correlation from 2-NH to C-5. Three additional fragments, H-23/H-14/H-15, H-24/H-16 and H-21/H-22, were recognized from the COSY spectrum. HMBC correlations from H-23 to C-13, C-14 and C-15, and from H-24 to C-15, C-16 and C-17, established the 2,4-dimethyl-3-hydroxyalkanoate substructure. Connectivity of this fragment to the peptide unit was elucidated by HMBC correlations from 11-NH to C-13 and from H-15 to C-1. Finally, the fragment C-22/C-21 containing the triplet methyl group, the methylene fragment C-20 that had an HMBC correlation from H-22 and

Complete Stereochemistry and Preliminary Structure–Activity Relationship of Rakicidin A, a Hypoxia-Selective Cytotoxin from Micromonospora sp.

The complete stereochemistry of rakicidin A, a hypoxia-selective cytotoxin produced by Micromonospora sp., was unambiguously established by extensive chemical degradation and derivatization studies. During the PGME derivatization-based configurational analysis of 3-hydroxy-2,4,16-trimethylheptadecanoic acid, an irregular Δδ distribution was observed, which necessitated further acylation of the 3-hydroxy group to resolve the inconsistency. A hydrogenated derivative of rakicidin A, its ring-opened product, and two congeners with different alkyl chain lengths were tested for hypoxia-selective cytotoxicity. The results indicated that both the conjugated diene unit and appropriate chain length are essential for the unique activity of rakicidin A.

Anti-invasive and anti-angiogenic activities of naturally occurring dibenzodiazepine BU-4664L and its derivatives

In the screening for antitumor leads from microbial secondary metabolites, BU-4664L (1), a naturally occurring dibenzodiazepine, was found to inhibit tumor invasion and angiogenesis in vitro. Compound 1 inhibited the gelatinase activities of MMP-2 and MMP-9 and the cellular motility. Four derivatives (2-5) were synthesized from 1 and their antitumor activities were evaluated. Compounds 3 and 4 exhibited potent anti-angiogenic effects on HUVEC, together with remarkable inhibition of cell migration at nanomolar concentrations, and showed much lower cytotoxicity.

Synthesis and evaluation of myxochelin analogues as antimetastatic agents

Myxochelin A (1) is an inhibitor of tumor cell invasion produced by the bacterium belonging to the genus Nonomuraea. In order to obtain more potent inhibitors, a series of myxochelin analogues [2 and (S)-3-17] were synthesized through the coupling of lysine or diaminoalkane derivatives and appropriately protected hydroxybenzoate, followed by modification of functional groups and deprotection. These compounds were evaluated for their inhibitory activity against invasion of murine colon 26-L5 carcinoma cells. Among the synthetic analogues tested, compound (S)-6 which possesses carbamoyl group at C-1 was found to be the most potent antiinvasive agent and is considered to be a promising lead molecule for the antimetastasis. Compound (S)-6 was also shown to inhibit gelatinase activities of MMP-2 and MMP-9 and in vivo lung metastasis in mice.

Two butenolides with PPARα agonistic activity from a marine-derived Streptomyces.

Peroxisome proliferator-activated receptors (PPARs) are ligandactivated transcription factors classified into three subtypes known as PPARα, PPARβ (δ) and PPARγ.1 PPARs regulate the systemic energy metabolism by modulating the expression of numerous genes involved in lipid and glucose metabolism. Therefore, these nuclear transcription factors are recognized as ideal targets for the treatment of dyslipidemia, diabetes, and the cardiovascular disorders associated with obesity and the metabolic syndrome. In particular, PPARα is considered as a therapeutic target of dyslipidemic diseases as it mediates lipid lowering by activating a transcriptional cascade that induces genes involved in the catabolism of lipids.1 Marine-derived microorganisms have attracted significant attention for their potential of producing a wide array of secondary metabolites.2–4 During the course of our screening for bioactive compounds from marine-derived bacteria, glycosylated tetronates with apoptosis-inducing activity, a cytotoxic anthracycline derivative, herbicidal isocoumarins and adipogenic polyketides were discovered.5–8 As a part of our continuing study in this field, we screened for new scaffolds for PPARα agonists using a reporter gene assay and found two butenolides (1 and 2, Figure 1) from a marine-derived Streptomyces strain. The presence of compounds 1 and 2 was indicated by the GC/MS analysis of volatile components released from Streptomyces but their complete spectroscopic characterization, including the absolute configuration, was not reported.9 In this study, we attempted the absolute configuration assignment of these butenolides. We herein report the structure determination and biological activity of 1 and 2. The producing strain TP-A0873 was isolated from a seawater sample collected in Toyama Bay, Japan. The strain was cultured in A3M liquid medium and the whole culture broth was extracted with 1-butanol. The crude extract was fractionated by silica gel and octadecylsilyl (ODS) column chromatographies, followed by reversed-phase HPLC purification to yield butenolides 1 and 2. Compound 1 was obtained as a colorless oil, which had a molecular formula of C12H20O2 (three degrees of unsaturation) by interpretation of high-resolution ESITOFMS ([M+H]+ m/z 197.1535, Δ− 0.1 mmu, calcd for C12H21O2) and NMR data (Table 1). The IR spectrum of 1 indicated the presence of carbonyl functionality (1749 cm 1). 1H and 13C NMR analysis of 1 in combination with HSQC spectrum revealed the presence of 12 carbons including a carbonyl carbon, two olefinic carbons, an oxygen-bearing methine, five methylenes, a methine and two methyls (Table 2). As one double bond and one carbonyl accounted for two of the three double-bond equivalents, 1 must be a monocyclic compound. Analysis of 1H-1H COSY spectrum provided two spin systems consisting of protons from H2 to H7 and from H8 to H11. Two doublet methyl protons (H11 and H12) showed HMBC correlations to one another, to C10, and to C9, establishing the isopropyl terminus in the latter fragment. The two fragments were connected by HMBC correlations from H6 to C8 and H9 to C7. Furthermore, two olefinic protons (H2 and H3) showed correlation to the carbonyl carbon C1 (δ 173.2). Finally, consideration of the remaining unsaturation degree and the small coupling constant between the olefinic protons (J= 5.7 Hz) provided the α,β-unsaturated γ-lactone bearing a linear chain at the γ-position. This was consistent with the observed UV (λmax 206 nm) and IR data.10 The structure of 1 was thus assigned as 4-hydroxy-10-methylundec-2-en-1,4-olide. Compound 2 was isolated as a colorless oil. Its molecular formula was deduced as C13H22O2 from high-resolution ESITOFMS ([M+H] +