NRPS substrate promiscuity leads to more potent antitubercular sansanmycin analogues.

Sansanmycins, members of the uridyl peptide antibiotics, are assembled by nonribosomal peptide synthetases (NRPSs), the substrate promiscuity of which results in the diversity of products. Further exploration of the NRPSs' substrate promiscuity by reinvestigating sansanmycin producer strain led to the isolation and structural elucidation of eight new uridyl peptides, sansanmycins H-O (1-8). Among them, sansanmycin L, containing a 6-OH-bicyclic residue and Phe3 first found at the position AA3, exhibited activity against M. tuberculosis H37Rv with an MIC value of 2 µg/mL, 8-fold more potent than that of the major compound, sansanmycin A (MIC = 16 µg/mL).

Reverse Zagreb Indices and Their Application in the Evaluation of Physiochemical Properties of Anticancer/Antibacterial Drugs.

Recent advancements in chemical graph theory have facilitated a deeper understanding of the relationship between chemical structures and their underlying graphs based upon classical graph theory principles. Quantitative structure-property relationship (QSPR) analysis stands out as a powerful tool for probing chemical graphs. Topological indices, graph invariants assigning numerical values to graphs, play a pivotal role in statistically correlating physical properties, chemical reactivity, and biological activity across diverse chemical structures. The cactus graph (CG) represents a noteworthy family of connected graphs distinguished by the absence of common vertices between cycles. In this study, we focus on establishing the expressions of Zagreb and reverse Zagreb indices in terms of known parameters for cactus graphs. Subsequently, we leverage these indices to conduct QSPR analysis, employing linear and multilinear regression models to investigate the relationship between the properties of chemical structures adorned with cactus-like graphs and the corresponding Zagreb and reverse Zagreb indices.

SsaA, a member of a novel class of transcriptional regulators, controls sansanmycin production in Streptomyces sp. strain SS through a feedback mechanism.

Sansanmycins, produced by Streptomyces sp. strain SS, are uridyl peptide antibiotics with activities against Pseudomonas aeruginosa and multidrug-resistant Mycobacterium tuberculosis. In this work, the biosynthetic gene cluster of sansanmycins, comprised of 25 open reading frames (ORFs) showing considerable amino acid sequence identity to those of the pacidamycin and napsamycin gene cluster, was identified. SsaA, the archetype of a novel class of transcriptional regulators, was characterized in the sansanmycin gene cluster, with an N-terminal fork head-associated (FHA) domain and a C-terminal LuxR-type helix-turn-helix (HTH) motif. The disruption of ssaA abolished sansanmycin production, as well as the expression of the structural genes for sansanmycin biosynthesis, indicating that SsaA is a pivotal activator for sansanmycin biosynthesis. SsaA was proved to directly bind several putative promoter regions of biosynthetic genes, and comparison of sequences of the binding sites allowed the identification of a consensus SsaA binding sequence, GTMCTGACAN2TGTCAGKAC. The DNA binding activity of SsaA was inhibited by sansanmycins A and H in a concentration-dependent manner. Furthermore, sansanmycins A and H were found to directly interact with SsaA. These results indicated that SsaA strictly controls the production of sansanmycins at the transcriptional level in a feedback regulatory mechanism by sensing the accumulation of the end products. As the first characterized regulator of uridyl peptide antibiotic biosynthesis, the understanding of this autoregulatory process involved in sansanmycin biosynthesis will likely provide an effective strategy for rational improvements in the yields of these uridyl peptide antibiotics.

Draft genome sequence of Streptomyces sp. strain SS, which produces a series of uridyl peptide antibiotic sansanmycins.

Streptomyces sp. SS produces a series of uridyl peptide antibiotic sansanmycins. Here, we present a draft genome sequence of Streptomyces sp. SS containing the biosynthetic gene cluster for the antibiotics. The identification of the biosynthetic gene cluster of sansanmycins may provide further insight into biosynthetic mechanisms for uridyl peptide antibiotics.

A marine-derived Streptomyces sp. MS449 produces high yield of actinomycin X2 and actinomycin D with potent anti-tuberculosis activity.

In the course of our screening program for anti-Mycobacterium bovis bacillus Calmette-Guérin (BCG) and anti-Mycobacterium tuberculosis H37Rv (MTB H37Rv) agents from our marine natural product library, a newly isolated actinomycete strain, designated as MS449, was picked out for further investigation. The strain MS449, isolated from a sediment sample collected from South China Sea, produced actinomycin X(2) and actinomycin D in substantial quantities, which showed strong inhibition of BCG and MTB H37Rv. The structures of actinomycins were elucidated by nuclear magnetic resonance and mass spectrometric analysis. The strain MS449 was taxonomically characterized on the basis of morphological and phenotypic characteristics, genotypic data, and phylogenetic analysis. The 16S rRNA gene sequence of the strain was determined and a database search indicated that the strain was closely associated with the type strain of Streptomyces avermitilis (99.7 % 16S rRNA gene similarity). S. avermitilis has not been previously reported to produce actinomycins. The marine-derived strain of Streptomyces sp. MS449 produced notably higher quantities of actinomycin X(2) (1.92 mg/ml) and actinomycin D (1.77 mg/ml) than previously reported actinomycins producing strains. Thus, MS449 was considered of great potential as a new industrial producing strain of actinomycin X(2) and actinomycin D.

[In vivo distribution of FITC-labeled boanmycin hydrochloride in situ gel].

This study is to evaluate the sustained-release effect of the thermosensitive in situ gel for injection of boanmycin hydrochloride (BAM) by bioluminescence imaging in nude mice. BAM was labeled with fluorescein isothiocyanate (FITC). The FITC-labeled BAM (FITC-BAM) was purified by dialysis and Sephadex G25 gel column, and then was identified by matrix-assisted laser desorption ionization/time of flight (MALDI-TOF). The model of experimental hepatoma HepG-2 nude mice was established, and the optical imaging system was applied to evaluate the distribution of FITC-BAM in vivo. Results of MALDI-TOF proved that the major molecular ratio of BAM : FITC was 1 : 1 or 1 : 2. Bioluminescence imaging showed that the diffusion of FITC-BAM in situ gel group was significantly delayed compared with the negative control group. This study demonstrated that the thermosensitive in situ gel can effectively delay the release of boanmycin hydrochloride, and extend the retention time in vivo.

Potent antitumor actions of the new antibiotic boningmycin through induction of apoptosis and cellular senescence.

Boningmycin, a new antibiotic of the bleomycin family, is isolated from the fermentation broth of Streptomyces verticillus var. pingyangensis n.sp. This study aimed to evaluate its antitumor actions and mechanism. The results showed that boningmycin exhibited potent inhibitory effects on several human solid tumor cells and that it was stronger than bleomycin. The administration of boningmycin inhibited the growth of human hepatoma HepG2 xenografts in nude mice, with more efficacy than that of bleomycin. Boningmycin led to an increase of the reactive oxygen species involving iron and caused G2/M phase accumulation in the HepG2 and human breast cancer MCF-7 cells. Two types of cell death, apoptosis and senescence, were detected after exposure to boningmycin. The accumulation of sub-G1 phase cells, an index of apoptosis, and the activation of caspase apoptotic pathways were detected after treatment with higher concentrations of boningmycin. Low concentrations of boningmycin led to a senescent phenotype with an increase in senescence-associated ß-galactosidase activity and the time-dependent increase of p21, p27, and p53 expressions from 48 to120 h. Taken together, the results showed that boningmycin exhibits potent antitumor actions through the induction of apoptosis and cellular senescence.

Synthesis and in vitro antitubercular evaluation of novel sansanmycin derivatives.

Tuberculosis (TB) is a major health problem worldwide. A series of novel sansanmycin derivatives were designed, semi-synthesized and evaluated for their activity against drug-susceptible Mycobacterium tuberculosis strain H(37)Rv with sansanmycin A (SSA) as the lead. Among these analogs tested, compound 1d possessing an isopropyl group at the amino terminal afforded an increased antimycobacterial activity with a MIC value of 8 µg/mL in comparison with SSA. Importantly, it was active for rifampicin- and isoniazid-resistant M. tuberculosis strain isolated from patients in China. These promising results offer an opportunity for further exploration of this novel class of analogs as antitubercular agents.

[Thermosensitive in situ gel of boanmycin hydrochloride for injection].

Poloxamer F127, poloxamer F68 and hydroxypropyl methylcellulose K4M were used to prepare the thermosensitive in situ gel of boanmycin hydrochloride for injection. Its gelation temperature, rheological behavior, texture characteristics, scanning electron microscopy, in vitro and in vivo drug release were evaluated. These results showed that the formulation was a fluid solution at room temperature, which could become semisolid at the temperature of 37 degrees C, and the thermally induced sol-gel transition allowed to be injectable and in situ setting. The formulation was constructed into a tridimensional network at gelation temperature. The drug release was controlled by the diffusion of the drug and the erosion of the gelmatrix. The pharmacokinetics indicated that the drug could be released slowly for up to 48 hours after subcutaneous administration in rats.

[Characteristics of boningmycin induced cellular senescence of human tumor cells].

Cellular senescence is one of the important steps against tumor. This study was to observe the characteristics of boningmycin induced senescence of human tumor cells. MIT method and clone formation assay were used to detect the growth-inhibitory effect. Cellular senescence was detected with senescence-associated beta-galactosidase staining. Cell cycle distribution and accumulation of intracellular reactive oxygen species (ROS) were analyzed with flow cytometry. Protein expression was detected by Western blotting. The results showed that the growth-inhibitory effect of boningmycin was obviously stronger on human oral epithelial carcinoma KB cells than that on non-small cell lung cancer A549 cells. Comparison to the similar action of doxorubicin, that boningmycin induced the features of cellular senescence in both cell lines, its due to the arrest at G2/M phase and an increase of ROS level. The molecular senescence marker P21 increased significantly after boningmycin treatment at a dosage of 0.1 micromol x L(-1), whereas a higher concentration of it induced apoptosis. The results indicated that cellular senescence induced by boningmycin was one of its mechanisms in tumor suppression.

Effects of combined treatment with sansanmycin and macrolides on Pseudomonas aeruginosa and formation of biofilm.

OBJECTIVE: To observe the effects of combined treatment with sansanmycin and macrolides on Pseudomonas aeruginosa and formation of biofilm. METHODS: Micro-dilution method was used to determine the minimal inhibitory concentrations (MICs) of sansanmycin, gentamycin, carbenicillin, polymyxin B, roxithromycin, piperacillin, and tazobactam. PA1 and PA27853 biofilms were observed under optical microscope after staining and under SEM after treatment with sansanmycin at different dosages and combined treatment with sansanmycin and roxithromycin. Viable bacteria in PA1 and PA27853 biofilms were counted after treatment with sansanmycin at different dosages or combined treatment with sansanmycin and roxithromycin. RESULTS: The MIC of sansanmycin was lower than that of gentamycin and polymyxin B, but was higher than that of carbenicillin. Roxithromycin enhanced the penetration of sansanmycin to PA1 and PA27853 strains through biofilms. PA1 and PA27853 biofilms were gradually cleared with the increased dosages of sansanmycin or with the combined sansanmycin and roxithromycin. CONCLUSION: Sub-MIC levels of roxithromycin and sansanmycin substantially inhibit the generation of biofilms and proliferation of bacteria. Therefore, combined antibiotics can be used in treatment of intractable bacterial infection.

Sansanmycins B and C, new components of sansanmycins.

Two new antibiotics, sansanmycins B and C, were isolated from Streptomyces sp. SS. Their structures were elucidated by extensive 1D and 2D NMR and MS spectral analyses. Sansanmycins B and C exhibited inhibitory activity against our test strain of Pseudomonas aeruginosa with MIC values of 8.0 and 16 microg/ml, respectively. Sansanmycin B also exhibited inhibitory activity against Mycobacterium tuberculosis H37Rv and multidrug-resistant Mycobacterium tuberculosis, with the MIC values ranging from 8.0 to 20 microg/ml.

Isolation and characterization of antibiotic NC0604, a new analogue of bleomycin.

NC0604, a new analogue of bleomycin, was isolated from fermentation broth of Streptomyces verticillus var. pingyangensis n.var. The structure of NC0604 was elucidated by spectroscopic analyses. NC0604 had the same kernel structure as bleomycin, but a different terminal amine moiety determined as amidepropyl spermidine. NC0604 exhibited antibacterial activity against a wide range of bacterial species and showed cytotoxicity in vitro against human HepG(2), KB, MCF-7, HCT116, BGC-823 and MCF-7/DOX cells with IC(50) values of 1.18, 1.21, 1.41, 1.83, 2.02, 1.45 muM, respectively. The antitumor activity of NC0604 against these cells was 3~9 times higher than that of bleomycin; and the pulmonary toxicity of NC0604 was much lower than that of bleomycin.

A new nucleosidyl-peptide antibiotic, sansanmycin.

A new nucleosidyl-peptide antibiotic, sansanmycin, was isolated from an unidentified Streptomyces sp SS. The structure of sansanmycin was elucidated by analyses of its alkaline hydrolysate and spectroscopic analyses. Sansanmycin exhibits antibacterial activity against Mycobacterium tuberculosis H(37)Ra and Pseudomonas aeruginosa with MIC values of 10 and 12.5 mug/ml, respectively.

Discovery, synthesis and biological evaluation of cycloprotoberberine derivatives as potential antitumor agents.

A series of new 1,13-cycloprotoberberine derivatives defined through variations at the 9-position were designed, synthesized and evaluated for their cytotoxicities in human HepG2 (hepatoma), HT1080 (fibrosarcoma) and HCT116 (colon cancer) cells. The preliminary structure-activity relationship (SAR) revealed that the replacement of 9-methoxyl with an ester moiety might significantly enhance the antiproliferative activity in vitro. Notably, compound 7f demonstrated equipotent cytotoxicity activity against breast cancer MCF-7 (parent) and doxorubicin (DOX)-resistant MCF-7 (MCF-7/ADrR) cells, indicating a mode of action different from that of DOX. Further mechanism study showed that 7f significantly inhibited activity of DNA topoisomerase I (Top I) and Top II. G2/M phase arrest and tumor cell growth reduction was observed thereafter. Thus, we consider cycloprotoberberine analogues to be a new family of promising antitumor agents with an advantage of inhibiting drug-resistant cancer cells.

Mechanisms of the antitumor action of the new antibiotic NC0604, a member of the bleomycin family.

NC0604, the new antibiotic of the bleomycin family, was isolated from the fermentation broth of Streptomyces verticillus var. pingyangensis n.sp. In this study, we investigated its mechanisms of antitumor action in vitro and in vivo. The results showed that the colony formation inhibition of NC0604 was 2-10 times higher than that of bleomycin to several tumor cell types. In comparison to bleomycin, a better antitumor efficacy of NC0604 was observed in the BALB/c mice loading mouse hepatoma H22 tumors. Flow cytometry assay detected an increase of intracellular reactive oxygen species and arrest at G2/M phase in human hepatoma HepG2 cells after exposure to NC0604. The comet of DNA damage was also observed in the NC0604-treated cells using single cell gel electrophoresis assay. The chromatin condensation appeared in the NC0604-induced apoptotic cells. The activation of apoptotic caspase pathway and increase of apoptosis-modulated protein expression, such as p53, Bax, were also detected by Western blot analysis. Taken together, the anti-tumor actions of NC0604 involve activation of the apoptotic pathway and it is valuable for further drug development.