Pilar Rodríguez

Molecular characterization of the safracin biosynthetic pathway from Pseudomonas fluorescens A2‐2: designing new cytotoxic compounds

Safracin is an antibiotic with anti‐tumour activity produced by Pseudomonas fluorescens A2‐2. The entire safracin synthetic gene cluster spanning 17.5u2003kb has been identified, cloned and sequenced. The safracin cluster comprises 10 open reading frames (ORFs) encoding proteins for three non‐ribosomal peptide synthetases (NRPS), three safracin precursor biosynthetic enzymes, two safracin tailoring enzymes, a safracin resistance protein and a small hypothetical protein of unknown function. These genes are organized in two divergent operons of eight and two genes respectively. This pathway exhibits unusual features when compared with other NRPS systems. We have demonstrated by heterologous expression of the cluster that it is able to direct the synthesis of safracin in other strains. Cross‐feeding experiments have confirmed that 3‐hydroxy‐5‐methyl‐O‐methyltyrosine is the precursor of two amino acids of the molecule. Genetic analyses have allowed us to demonstrate that the bicistronic operon encodes the hydroxylation and N‐methylation activities of the pathway. The cloning and expression of the safracin cluster has settled the basis for the in vivo and in vitro production of a wide variety of compounds, such as the promising ecteinascidins anti‐cancer compounds.

Tartrolon D, a Cytotoxic Macrodiolide from the Marine-Derived Actinomycete Streptomyces sp. MDG-04-17-069

Exploration of marine-derived actinomycetes as a source of antitumor compounds has led to the isolation of a new member of the tartrolon series, tartrolon D (4). This new compound was obtained from Streptomyces sp. MDG-04-17-069 fermentation broths and displayed strong cytotoxic activity against three human tumor cell lines. Additionally, the known compound ikarugamycin (5) was also found in the culture broths of the same microorganism. The structure of this new tartrolon was established by a combination of spectroscopic techniques (1D and 2D NMR, HRMS, and UV) as well as by comparison with published data for similar compounds.

Antitumor actinopyranones produced by Streptomyces albus POR-04-15-053 isolated from a marine sediment.

Four new antitumor pyranones, PM050511 (1), PM050463 (2), PM060054 (3), and PM060431 (4), were isolated from the cell extract of the marine-derived Streptomyces albus POR-04-15-053. Their structures were elucidated by a combination of spectroscopic methods, mainly 1D and 2D NMR and HRESIMS. They consist of an α-methoxy-γ-pyrone ring containing a highly substituted tetraene side chain glycosylated at C-10 in the case of 1 and 4. Compounds 1 and 4 displayed strong cytotoxicity against three human tumor cell lines with GI₅₀ values in the submicromolar range, whereas 2 showed subnanomolar activity as an inhibitor of EGFR-MAPK-AP1-mediated mitogenic signaling, causing inhibition of EGF-mediated AP1 trans-activation and EGF-mediated ERK activation and slight inhibition of EGF-mediated JNK activation. Taken together, these results suggest that members of the pyranone family of compounds could be developed as potential antitumor agents.

PM070747, a new cytotoxic angucyclinone from the marine-derived Saccharopolyspora taberi PEM-06-F23-019B.

PM070747, a new cytotoxic angucyclinone from the marine-derived Saccharopolyspora taberi PEM-06-F23-019B

PM100117 and PM100118, new antitumor macrolides produced by a marine Streptomyces caniferus GUA-06-05-006A.

Two new bioactive polyhydroxyl macrolide lactones PM100117 (1) and PM100118 (2) were isolated from the culture broth of the marine-derived Streptomyces caniferus GUA-06-05-006A. Their structures were elucidated by a combination of spectroscopic methods, mainly one-dimensional and 2D NMR and HRESI-MS. They consist of 36-membered macrolides with a side chain containing three deoxy sugars and a 1,4-naphthoquinone chromophore. Compounds 1 and 2 displayed potent cytotoxicity against three human tumor cell lines with GI50 values in the micromolar range, as well as slight antifungal activity against Candida albicans ATCC10231. In addition, both compounds alter the plasma membrane of tumor cells, inducing loss of membrane integrity and subsequent cell permeabilization leading to a fast and dramatic necrotic cell death.

Bacterial Production of a Pederin Analogue by a Free-Living Marine Alphaproteobacterium

The polyketide pederin family are cytotoxic compounds isolated from insects, lichen, and marine sponges. During the past decade, different uncultivable bacteria symbionts have been proposed as the real producers of these compounds, such as those found in insects, lichen, and marine sponges, and their trans-AT polyketide synthase gene clusters have been identified. Herein we report the isolation and biological activities of a new analogue of the pederin family, compound 1, from the culture of a marine heterotrophic alphaproteobacterium, Labrenzia sp. PHM005. This is the first report of the production of a pederin-type compound by a free-living marine bacteria that could be cultured in the laboratory.

Streptenols F–I Isolated from the Marine-Derived Streptomyces misionensis BAT-10-03-023

A marine-derived bacterium, Streptomyces misionensis BAT-10-03-123, has produced four new streptenol derivatives, F, G, H, and I (1-4), as well as the known streptenols A and C (5 and 6). Their planar structures were elucidated by detailed analysis of spectroscopic data. The absolute configurations of the new streptenol compounds were determined by chemical and spectroscopic methods, including Moshers ester method. All of the compounds were tested for cytotoxicity against four selected cancer cell lines.