Thiciana S. Sousa

Kocurin, the True Structure of PM181104, an Anti-Methicillin-Resistant Staphylococcus aureus (MRSA) Thiazolyl Peptide from the Marine-Derived Bacterium Kocuria palustris

A new thiazolyl peptide, kocurin (1), was isolated from culture broths of a marine-derived Kocuria palustris. Its structural elucidation was accomplished using a combination of spectroscopic and chemical methods, including HRMS, extensive 1D and 2D NMR analysis, MS/MS fragmentation, and chemical degradation and Marfey’s analysis of the resulting amino acid residues. The structure herein reported corrects that previously assigned to PM181104 (3). Kocurin displayed activity against methicillin-resistant Staphylococcus aureus (MRSA), with MIC values in the submicromolar range.

Anthracyclinones from Micromonospora sp.

Four new anthracyclinones, 4,6,11-trihydroxy-9-propyltetracene-5,12-dione (1), 1-methoxy-9-propyltetracene-6,11-dione (2), 7,8,9,10-tetrahydro-9-hydroxy-1-methoxy-9-propyltetracene-6,11-dione (3), and 10β-carbomethoxy-7,8,9,10-tetrahydro-4,6,7α,9α,11-pentahydroxy-9-propyltetracene-5,12-dione (4), were isolated from a strain of Micromonospora sp. associated with the tunicate Eudistoma vannamei. All structures were established by 1D and 2D NMR (COSY, HSQC, HMBC, NOESY) and HRESIMS experiments. Compounds 1 and 4 were cytotoxic against the HCT-8 human colon adenocarcinoma cell line, with IC(50) values of 12.7 and 6.2 μM, respectively, while compounds 2 and 3 were inactive.

Pseudomonas soli sp. nov., a novel producer of xantholysin congeners

A chemoorganotrophic Gram-negative bacterium was isolated by means of a diffusion sandwich system from a soil sample from the Sierra Nevada National Park, Spain. Strain F-279,208(T) was oxidase and catalase positive, strictly aerobic, non-spore-forming and motile by single polar flagellum. Phylogenetic analysis of the 16S rRNA, gyrB, rpoB and rpoD genes revealed that strain F-279,208(T) belongs to the Pseudomonas putida group with Pseudomonas mosselii and Pseudomonas entomophila as its closest relatives. DNA-DNA hybridization assays and phenotypic traits confirmed that this strain belongs to a novel species of the genus Pseudomonas, for which the name Pseudomonas soli sp. nov. is proposed. The type strain is F-279,208(T) (=DSM 28043(T)=LMG 27941(T)), and during fermentation it produces xantholysins, a family of lipodepsipeptides. The major compound, xantholysin A, showed an interesting activity in a RCC4 kidney tumor cell line with inactivation of VHL linked with the HIF pathway, without any cytotoxic effects against other human tumor cell lines tested including, liver, pancreas and breast.

Cytotoxic Plakortides from the Brazilian Marine Sponge Plakortis angulospiculatus.

Three new plakortides, 7,8-dihydroplakortide E (1), 2, and 10, along with known natural products 3, 4, spongosoritin A (5), 6-8, and plakortide P (9), were isolated from Brazilian specimens of Plakortis angulospiculatus. Compounds 2, 3, 5, and 7-9 displayed cytotoxic activities with IC50 values ranging from 0.2 to 10 μM. Compounds that contained a dihydrofuran ring were generally less active and displayed time dependence in their activity. The activities of compounds 2 and 7-9, carboxylic acids bearing a common six-membered endoperoxide, were higher overall than for compounds 3 and 5. The modes underlying the cytotoxic actions of plakortides 2, 3, 5, 7, and 9 were further investigated using HCT-116 cells. While dihydrofurans 3 and 5 induce a G0/G1 arrest, six-membered peroxides 2, 7, and 9 delivered a G2/M arrest and an accumulation of mitotic figures, indicating a distinctly different antimitotic response. Confocal analysis indicated that microtubules were not altered after treatment with 2, 7, or 9, therein suggesting that the mitotic arrest may be unrelated to cytoskeletal targets. Overall, we find that two related classes of natural products obtained from the same extract offer cytostatic activity, yet they do so through discrete pathways.

Studies on the secondary metabolites of a Pseudoalteromonas sp. isolated from sediments collected at the northeastern coast of Brazil.

Continuing search for anticancer compounds from the marine environment, we have studied microorganisms that inhabit intertidal sediments of the northeastern Brazilian coast. Of the 32 strains isolated, 13 were selected for biological evaluation of their crude extracts. The acetate extract obtained from a Gram‐negative bacterium was strongly active against cancer cell lines with IC50 values that ranged from 0.04 (HL60 leukemia cells) to 0.26 μg/ml (MDA MB‐435 melanoma cells). The bacterium was identified as a Pseudoalteromonas sp. based on 16S rRNA gene sequencing. A bioassay‐guided fractionation of the active extract led to the isolation of prodigiosin, a well‐known tripyrrole red pigment with immunosuppressive and anticancer activities. Further experiments with ErbB‐2 overexpressing cell lines, including HB4a‐C3.6 (moderate overexpression), HB4a‐C5.2 (high overexpression), and the parental HB4a cell line, were performed. Prodigiosin was moderately active toward HB4a cells with an IC50 of 4.6 μg/ml, while it was 115 and 18 times more active toward HB4a‐C3.6 cells (IC50 of 0.04 μg/ml) and HB4a‐C5.2 (IC50 of 0.26 μg/ml) cells, respectively. These data suggest that, in spite of its previously described apoptosis‐inducing properties, prodigiosin can selectively recognize cells overexpressing ErbB‐2, which could be highly appealing in human breast cancer therapy.

Identification of the Lipodepsipeptide MDN-0066, a Novel Inhibitor of VHL/HIF Pathway Produced by a New Pseudomonas Species

Throughout recent history, metabolites of microbial origin have had an extraordinary impact on the welfare of humanity. In fact, natural products have largely been –and still are– considered an exceedingly valuable platform for the discovery of new drugs against diverse pathologies. Such value is partly due to their higher complexity and chemical diversity as compared to those of synthetic and combinatorial compounds. Mutations in the Von Hippel-Lindau (vhl) gene are responsible for VHL disease, congenital polycythemia, and are found in many sporadic tumor types. The primary cause of morbidity and mortality for these patients arises from progression of Renal Cell Carcinoma (RCC) or end-stage renal disease. Inactivation of the Von Hippel-Lindau (vhl) tumor suppressor gene arises in the majority of Renal Cell Carcinoma (RCC) as well as in other types of cancer and is associated with a high degree of vascularization and poor prognosis. Loss of pVHL function thus represents a pathognomonic molecular defect for therapeutic exploitation. In this study, renal carcinoma cell lines with naturally occurring vhl mutations (RCC4 VA) and their genetically matched wild-type vhl (RCC4 VHL) counterparts were seeded onto 96-well plates and treated with a collection of 1,040 organic extracts obtained from 130 bacterial strains belonging to at least 25 genera of the phyla Actinobacteria, Firmicutes, Proteobacteria and Bacteroidetes. This strategy allowed us to identify several extracts obtained from bacterial strain F-278,770T, the type strain of the recently proposed new species Pseudomonas granadensis, showing biological activities not associated with previously known bioactive metabolites. The fractionation and structural elucidation of one of these extracts led to the discovery of a new lipodepsipeptide (MDN-0066) with specific toxicity in pVHL deficient cells that is not detectable in cells with pVHL expression rescue. This specific toxicity is associated with apoptosis induction in VHL deficient cell line as demonstrated with PARP activation and Annexin V staining. Our study demonstrated the feasibility of selectively targeting the loss of the vhl tumor suppressor gene for potential clinical benefit. Our results may have great impact on the development of new targeted therapies from natural products for the treatment of cancer and other genetic diseases.

Chromomycin A2 Induces Autophagy in Melanoma Cells

The present study highlights the biological effects of chromomycin A2 toward metastatic melanoma cells in culture. Besides chromomycin A2, chromomycin A3 and demethylchromomycin A2 were also identified from the extract derived from Streptomyces sp., recovered from Paracuru Beach, located in the northeast region of Brazil. The cytotoxic activity of chromomycin A2 was evaluated across a panel of human tumor cell lines, which found IC50 values in the nM-range for exposures of 48 and 72 h. MALME-3M, a metastatic melanoma cell line, showed the highest sensitivity to chromomycin A2 after 48h incubation, and was chosen as a model to investigate this potent cytotoxic effect. Treatment with chromomycin A2 at 30 nM reduced cell proliferation, but had no significant effect upon cell viability. Additionally, chromomycin A2 induced accumulation of cells in G0/G1 phase of the cell cycle, with consequent reduction of S and G2/M and unbalanced expression of cyclins. Chromomycin A2 treated cells depicted several cellular fragments resembling autophagosomes and increased expression of proteins LC3-A and LC3-B. Moreover, exposure to chromomycin A2 also induced the appearance of acidic vacuolar organelles in treated cells. These features combined are suggestive of the induction of autophagy promoted by chromomycin A2, a feature not previously described for chromomycins.

Identification of pyrroloformamide as a cytokinesis modulator.

Discovered in the late 1940s, the pyrrolinonodithioles represent a family of potent disulfide‐containing natural products. Although they are understood in a synthetic and biosynthetic context, the biological role of these materials remains unresolved. To date, their activity has been suggested to arise through regulating RNA metabolism, and more recently they have been suggested to function as backup thiols for detoxification. Using materials identified through a natural products program, we now identify the biological function of one member of this family, pyrroloformamide, as an antimitotic agent acting, in part, by disrupting cytokinesis.

Terpenoides e cumarinas de Jatropha ribifolia (Pohl) Baill

Eight compounds, including terpenoids (jatrophone, hydroxyjatrophone, 6-hydroxycyperene, cabraleadiol monoacetyl, and cabraleadiol) and coumarins (fraxetin, fraxidin, and isofraxidin), were isolated from Jatropha ribifolia (Euphorbiaceae). Their structures were established by 1D and 2D NMR (COSY, HSQC, and HMBC) spectra, HRESIMS and comparison with published data.

TERPENOIDS AND COUMARINS FROMJatropha ribifolia(Pohl) Baill

Eight compounds, including terpenoids (jatrophone, hydroxyjatrophone, 6-hydroxycyperene, cabraleadiol monoacetyl, and cabraleadiol) and coumarins (fraxetin, fraxidin, and isofraxidin), were isolated from Jatropha ribifolia (Euphorbiaceae). Their structures were established by 1D and 2D NMR (COSY, HSQC, and HMBC) spectra, HRESIMS and comparison with published data.