Prodigiosin Analogues Research Articles

Substrate Flexibility of the Flavin-Dependent Dihydropyrrole Oxidases PigB and HapB Involved in Antibiotic Prodigiosin Biosynthesis.

In the biosynthesis of the tripyrrolic pigment prodigiosin, PigB is a predicted flavin‐dependent oxidase responsible for the formation of 2‐methyl‐3‐amylpyrrole (MAP) from a dihydropyrrole. To prove which dihydropyrrole is the true intermediate, both possibilities, 5‐methyl‐4‐pentyl‐3,4‐dihydro‐2H‐pyrrole (5 a, resulting from transamination of the aldehyde of 3‐acetyloctanal) and 2‐methyl‐3‐pentyl‐3,4‐dihydro‐2H‐pyrrole (6, resulting from transamination of the ketone), were synthesised. Only 5 a restored pigment production in a strain of Serratia sp. ATCC 39006 blocked earlier in MAP biosynthesis. PigB is membrane‐associated and inactive when its transmembrane domain was deleted, but HapB, its homologue in Hahella chejuensis, lacks the transmembrane domain and is active in solution. Two colourimetric assays for PigB and HapB were developed, and the HapB‐catalysed reaction was kinetically characterised. Ten analogues of 5 a were synthesised, varying in the C2 and C3 side chains, and tested as substrates of HapB in vitro and for restoration of pigment production in Serratia ΔpigD in vivo. All lengths of side chain tested at C3 were accepted, but only short side chains at C2 were accepted. The knowledge that 5 a is an intermediate in prodigiosin biosynthesis and the ease of synthesis of analogues of 5 a makes a range of prodigiosin analogues readily available by mutasynthesis.

Characterization of a prodigiosin synthetase PigC from Serratia marcescens jx-1 and its application in prodigiosin analogue synthesis

Due to their diverse bioactive effects, prodigiosin and its analogues (prodiginines) have attracted a great deal of attention. In this study, a prodigiosin synthetase PigC catalyzing a condensation reaction to produce prodigiosin was cloned from Serratia marcescens jx-1 and overexpressed in Escherichia coli with a putative polypeptide of 888 amino acids. Its biochemical properties and applications in prodiginines synthesis were investigated. The purified enzyme had a specific activity of 6.96 U/mg and exhibited optimal activity at 10 °C and pH 7.5. The recombinant PigC performed good stability below 30 °C and at pH ranging from 6.0 to 8.5. This enzyme was activated by Ca2+, while inhibited by Cu2+. The kinetic analysis with 4-methoxy-2,2′-bipyrrole-5-carboxyaldehyde (MBC) and 2,4-dimethyl-3-ethylpyrrole (DMEP) as substrates yielded apparent Km of 23.4 and 4.2 μmol/L, respectively. The enzymatic catalysis using whole cells of recombinant E. coli harboring the PigC as catalyst in an aqueous organic solvent system resulted in 59.4% yield of prodigiosin analogues, which exhibited excellent antimicrobial properties against Staphylococcus aureus, Bacillus subtilis and E. coli. The results obtain here demonstrated the great potential of PigC for the biosynthesis of prodigiosin and its analogues.

Abstract 3830: Synthesis and anticancer activity of novel prodigiosin analogs

Abstract We recently reported that Prodigiosin is a potent p53 pathway restoring small molecule that acts through p73 and by interfering with p73:mutant p53 protein interaction (Hong et al., Cancer Research, 2014). Prodigiosin is the parent member of the tripyrrole alkaloid family of natural products that shows potent anti-cancer activity against tumors with mutated p53. To improve pharmacological and medicinal properties of Prodigiosin including p73 induction and restoration of the p53 pathway in tumors with mutated p53, two new series of analogs were synthesized. We introduced carboxylic group substituents either directly on the C-ring or on the side-chain of the C-ring. Carboxylic group allowed for further derivatization of Prodigiosin. A number of new analogs have been prepared and tested for their anticancer activity. Preliminary biological activity assay showed that new compounds inhibited cancer cell proliferation from 0.1 μM to 10 μM both in p53 mutated SW480 and wild-type HCT116 colorectal cancer cell lines. Some of the newly synthesized compounds can induce p53 transcriptional reporter activity in p53 mutated SW480 colorectal cancer cells. Our ongoing experiments are focused on the signaling mechanism of apoptosis induced by the new analogs, identification of molecular targets of the compounds, and in vivo studies of Prodigiosin analogues as single agents or in combination with chemotherapy or targeted therapy. Citation Format: Xiaobing Tian, Shengliang Zhang, Wafik S. El-Deiry. Synthesis and anticancer activity of novel prodigiosin analogs. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3830.

Zooshikella marina sp. nov. a cycloprodigiosin- and prodigiosin-producing marine bacterium isolated from beach sand.

A red-pigmented bacterium producing a metallic green sheen, designated strain JC333T, was isolated from a sand sample collected from Shivrajpur-Kachigad beach, Gujarat, India. Phylogenetic analyses based on the 16S rRNA gene sequence of strain JC333T showed highest sequence similarity to Zooshikella ganghwensis JC2044T (99.24 %) and less than 91.94 % similarity with other members of the class Gammaproteobacteria. DNA-DNA hybridizations between JC333T and Z. ganghwensis JC2044T showed low relatedness values of 19 ± 1.3 % (reciprocal 21 ± 2.2 %). The major respiratory quinone was ubiquinone-9 (Q9) and the polar lipid profile was composed of the major components diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, an unidentified aminophospholipid and an unidentified lipid. The presence of C16 : 1ω7c/C16 : 1ω6c, C16 : 0, C18 : 1ω7c and C12 : 0 as major fatty acids supported the affiliation of strain JC333T to the genus Zooshikella. Prodigiosin, cycloprodigiosin and eight other prodigiosin analogues were the pigments of JC333T. Characterization based on 16S rRNA gene sequence analysis, physiological parameters, pigment analysis, ubiquinone, and polar lipid and fatty acid compositions revealed that JC333T represents a novel species of the genus Zooshikella, for which the name Zooshikella marina sp. nov. is proposed. The type strain is JC333T ( = KCTC 42659T = LMG 28823T).

Characterisation of PigC and HapC, the prodigiosin synthetases from Serratia sp. and Hahella chejuensis with potential for biocatalytic production of anticancer agents

PigC and HapC catalyse the condensation of 4-methoxy-2,2′-bipyrrole-5-carbaldehyde (MBC) with 2-methyl-3-amylpyrrole (MAP) to give the bright red tripyrrolic prodigiosin, which has potent anticancer activity. We have cloned and over-expressed both enzymes and characterised their enzymic activity in vitro using both the natural substrates, MBC and MAP, and analogues of these substrates. Thus a range of prodigiosin analogues have been produced. Both PigC and HapC are membrane-associated enzymes and attempts to fully solubilise them using detergents led to inactivation. The enzymes are ATP-dependent but, unlike the enzymes to which they show the greatest similarity, the by-product is ADP not AMP. Two different slowly interconverting rotamers of prodigiosin exist and the spectral changes with time are consistent with isomerisation of the E,Z (or α) rotamer to the Z,Z (or β) rotameric form.

Exceptional Production of both Prodigiosin and Cycloprodigiosin as Major Metabolic Constituents by a Novel Marine Bacterium, Zooshikella rubidus S1-1

A Gram-negative, red-pigment-producing marine bacterial strain, designated S1-1, was isolated from the tidal flat sediment of the Yellow Sea, Korea. On the basis of phenotypic, phylogenetic, and genetic data, strain S1-1 (KCTC 11448BP) represented a new species of the genus Zooshikella. Thus, we propose the name Zooshikella rubidus sp. nov. Liquid chromatography and mass spectrometry of the red pigments produced by strain S1-1 revealed that the major metabolic compounds were prodigiosin and cycloprodigiosin. In addition, this organism produced six minor prodigiosin analogues, including two new structures that were previously unknown. To our knowledge, this is the first description of a microorganism that simultaneously produces prodigiosin and cycloprodigiosin as two major metabolites. Both prodigiosin and cycloprodigiosin showed antimicrobial activity against several microbial species. These bacteria were approximately 1.5-fold more sensitive to cycloprodigiosin than to prodigiosin. The metabolites also showed anticancer activity against human melanoma cells, which showed significantly more sensitivity to prodigiosin than to cycloprodigiosin. The secondary metabolite profiles of strain S1-1 and two reference bacterial strains were compared by liquid chromatography-mass spectrometry. Multivariate statistical analyses based on secondary metabolite profiles by liquid chromatography-mass spectrometry indicated that the metabolite profile of strain S1-1 could clearly be distinguished from those of two phylogenetically related, prodigiosin-producing bacterial strains.

Apoptosis of human lung adenocarcinoma A549 cells induced by prodigiosin analogue obtained from an entomopathogenic bacterium Serratia marcescens

An entomopathogenic bacterial strain SCQ1 was isolated from silkworm (Bombyx mori) and identified as Serratia marcescens via 16S rRNA gene analysis. This strain produces a red pigment that causes acute septicemia of silkworm. The red pigment of strain SCQ1 was identified as prodigiosin analogue (PGA) with various reported biological activities. In this study, we found that low concentration of PGA showed significant anticancer activity in human lung adenocarcinoma A549 cells, but has little effect in human bone marrow stem cells, in vitro. By exposure to different concentrations of PGA for 24 h, morphological changes and the MTT assay showed that A549 cell line was very sensitive to PGA, with IC(50) value about 2.2 mg/L. Early stage of apoptosis was detected by flow cytometry while A549 cells were treated with PGA for 4 and 12 h, respectively. The proportion of dead cells was increased with treatment time or the concentrations of PGA, but it was inversely proportional to that of apoptotic cells. These results indicate that PGA obtained from strain SCQ1 induces apoptosis in A549 cells, but the molecular mechanisms of cell death are complicated, and the S. marcescens strain SCQ1 may serve as a source of the anticancer compound, PGA.

Studies on culture condition of new marine bacterium Zooshikella sp. SY01

New marine bacterium Zooshikella sp. SY01, producer of prodigiosin, was isolated from the seawaters of Sanya Bay. The culture conditions of this bacterium were investigated. Zooshikella sp. SY01 was cultured in 2216E media which contained tryptophan, histidine, lactonic acid, camphor, limonene, casein, diphenyl guanidine, coumarin and 1,3-dinitrobenzene, respectively. After 5 days cultivation, the extracts of different culture broths were detected by direct infusion mass spectroscopy using positive ESI mode. As the results, tryptophan, histidine and casein didn’t show any observable influences on the biosynthesis of prodigiosin. Lactonic acid, camphor, limonene, diphenyl guanidine, coumarin could inhibit the bacterium growth and prodigiosin biosynthesis to a certain extent, slower the culture broth to turn red. However, 1,3-dinitrobenzene inhibited the bacteria to produce prodigiosin completely. MS data suggested that various metabolites with chemodiversity were produced in different culture media. In particular, a series of high-molecular-weight compounds with high relative abundances were observed in the medium containing limonene. To further optimize the culture condition, more new prodigiosin analogues and lead compounds can be obtained and the goal of “one strain-many compounds” can be achieved.

Effects of antifungal agents on red tide phytoplankton: possibility of a novel preventive tool

Harmful algal blooms (HABs) are having signi¢cant impacts on coastal and estuarine areas, aiecting the health of aquatic organisms and population growth, ecology and even humans (Anderson1997). Because the HABs often cause acute shell¢sh poisonings and mass mortalities of aquatic organisms depending on the causative species of HABs, the impacts of HABs on aquatic industries and economies are serious problems (Landsberg 2002). Aquaculture is an important industry as a source of seafood. Aquaculture operations are carried out around coastal areas, and also red tides occurring near the shore frequently cause mass mortality of cultured ¢sh. Chattonella marina (Raphidophyceae) and Heterocapsa circularisquama (Dino£agellata) are known to have lethal eiects on ¢sh and shell¢sh, respectively (Matsuyama 1999; Landsberg 2002). There is no eiective prevention against causative red tide phytoplankton. In our previous study, a useful marine bacterium was isolated during screening for antifungal compounds (Nakashima, Kurachi, Kato,Yamaguchi & Oda 2005; Nakashima, Kato,Yamaguchi & Oda 2005). This marine bacterium produced a prodigiosin analogue that had antifungal activity against dermatophytes (Nakashima, Kato et al. 2005). In addition, the prodigiosin analogue also showed potent algicidal activity against red tide phytoplankton (Nakashima, Miyazaki, Matsuyama, Muraoka, Yamaguchi & Oda 2006). The phytoplankton may have common target sites that antifungal agents act on dermatophytes. It is possible that antifungal agents are novel preventive materials against red tide phytoplankton. Therefore, to con¢rm the hypothesis, we investigated the eiects of commercial antifungal agents (Fig. 1) on red tide phytoplankton. Bifonazole (BFZ), terbina¢ne hydrochloride (TBF), cholesterol and ergosterol (Fig. 1) were purchased fromWako Pure Chemical Industries (Tokyo, Japan). Stock solutions of antifungal agents were prepared with dimethyl sulfoxide to a concentration of 10mgmL . Axenic cultures of C. marina and H. circularisquamawere maintained at 26 1C in Erd-Schreiber modi¢ed (ESM) medium (pH 8.2) under illumination from a £uorescent lamp (30 mmol photonsm 2 S ) with a cycle of 12 h light and 12 h dark as described previously (Nakashima et al. 2006). To determine the algicidal activities of antifungal agents against C. marina and H. circularisquama, the stock solution of each antifungal agent (10mgmL ) was diluted 500-fold in ESMmedium, and serial twofold dilutions in ESM medium were prepared. Red tide phytoplankton in the logarithmic growth phase were diluted with ESM medium to a density of 2 10 cells mL . ESM media (500 mL) with various concentrations of antifungal agent were added to each algal cell suspension (500 mL) in the wells of a 24-well plate.The ¢nal concentrations of antifungal agents ranged from 10 to 0.01 mgmL . After incubating at 26 1C for 24 h, the number of viable algal Aquaculture Research, 2008, 39, 1346^1350 doi:10.1111/j.1365-2109.2008.01998.x

Chemoenzymatic synthesis of prodigiosin analogues—exploring the substrate specificity of PigC

Analogues of prodigiosin, a tripyrrolic pigment produced by Serratia species with potent immunosuppressive and anticancer activities, have been produced by feeding synthetic analogues of the normal precursor MBC to mutants of Serratia sp. ATCC 39006 or to engineered strains of Escherichia coli; in this way it has been shown that the prodigiosin synthesising enzyme, PigC, has a relaxed substrate-specificity.

A Prodigiosin Analogue Inactivates NADPH Oxidase in Macrophage Cells by Inhibiting Assembly of p47phox and Rac

Prodigiosins are natural red pigments that have multi-biological activities. Recently, we discovered a marine bacterial strain, which produces a red pigment. Extensive two-dimensional nuclear magnetic resonance and mass spectrometry analysis showed that the pigment is a prodigiosin analogue (PG-L-1). Here, we investigated the effect of PG-L-1 on NADPH oxidase activity in macrophage cells. PG-L-1 significantly inhibited superoxide anion (O(2)(-)) production by phorbol 12-myristate 13-acetate (PMA)-stimulated RAW 264.7 cells, a mouse macrophage cell line. The ED(50) value was estimated to be approximately 0.3 microM. PG-L-1 had no direct scavenging effect on O(2)(-) generated by hypoxanthine/xanthine oxidase system in electron spin resonance-spin trapping determinations, suggesting that this compound directly acts on the O(2)(-) production system, NADPH oxidase, in macrophage cells. We further investigated the effect of PG-L-1 on the behaviour of the cytosolic components of the NADPH oxidase, p67(phox), p47(phox), p40(phox), Rac and protein kinase C (PKC), in PMA-stimulated RAW 264.7 cells. Although PG-L-1 showed no effect on the activation of PKC, the immunoblotting analysis using specific antibodies showed that PG-L-1 strongly inhibits the association of p47(phox) and Rac in the plasma membrane of PMA-stimulated RAW 264.7 cells. These results suggest that PG-L-1 inactivates NADPH oxidase through the inhibition of the binding of p47(phox) and Rac to the membrane components of NADPH oxidase.

Role of interleukin-2 regulated proteins in immunosuppression by the N-alkylated prodigiosin analogue

Prodigiosins have emerged as a novel family of tripyrrole compounds with significant T cell specific immunosuppressive potential. We had previously reported the immunosuppressive activity of a novel N-alkylated prodigiosin analogue, 2,2′-[3-methoxy-1′amyl-5′-methyl-4-(1″-pyrryl)] dipyrryl-methene (MAMPDM) in mitogen stimulated spleen cells. There was an increase in the accumulation of IL-2 and induction of apoptotic cell death. Since IL-2 regulates both cellular proliferation and activation induced cell death (AICD), we have investigated the effect of MAMPDM on the expression of IL-2 regulated genes that are involved in these two opposite processes. The mitogen stimulated mouse spleen cells did not undergo a single division in presence of proliferation inhibitory concentrations of MAMPDM. An increase in the percentage of apoptotic cells was observed in the undivided cell population. The cells were arrested in G1 phase independent of the p53 expression. Expression of IL-2 regulated genes such as CD71, proliferating cell nuclear antigen (PCNA) and cyclin D was suppressed while that of Fas was not. Thus, in the presence of MAMPDM there was selective inhibition of only the pro-mitogenic signaling and not that of pro-apoptotic signaling by IL-2. The induction of apoptosis in presence of MAMPDM was the effect rather than cause for the anti-proliferative activity.

Tautomeric Equilibria in Phenolic A-Ring Derivatives of Prodigiosin Natural Products

The prodigiosin natural products contain a common 4-methoxy-pyrromethene chromophore that is attached to a pyrrole A-ring that has its lone-pair nitrogen electrons in conjugation with the pyrromethene entity. This feature is known to play a key role in the biological activities (anticancer, antimicrobial, and immunosuppressive) of the prodigiosins. In an attempt to alter or improve upon the therapeutic potential of the prodigiosins, we have synthesized two new isomeric analogues that contain phenolic A-ring systems (a para (p)-phenol; an ortho (o)-phenol with respect to the pyrromethene) with lone-pair oxygen electrons in conjugation with the pyrromethene chromophore of the natural product. Herein, we report on the optical properties of the phenolic prodigiosin analogues that have been measured using absorbance and steady-state emission spectroscopy. For both analogues absorption measurements in aprotic solvents show that the neutral (L) ligands exist as the enol tautomers with lambda(max) ~ 460 nm, as noted for the parent prodigiosin natural product. However, in polar protic solvents the phenolic derivatives undergo ground-state prototropic tautomerization to generate keto tautomers with lambda(max) ~ 530 nm. This unique feature for a prodigiosin analogue involves proton transfer from the phenolic OH to the pyrromethene N1 proton acceptor atom. Tautomeric equilibrium constants (KT) of 1.4 in 1:4 MeCN/H2O (v/v) have been determined from examination of the absorption spectra. Titration of the o-phenolic derivative with Zn(II) in methanol yielded a 40-fold increase in fluorescence intensity (lambda(max) 542 nm) and generated a new 1:1 complex with Zn(II) with a log K of 5.29, suggesting the potential utility of this analogue to act as a fluorescence probe in a biological matrix to monitor Zn(II) concentrations. Our results demonstrate that phenolic A-ring derivatives of prodigiosins possess some unique properties that may act to enhance the biological properties of the prodigiosin natural products.

A novel N-alkylated prodigiosin analogue induced death in tumour cell through apoptosis or necrosis depending upon the cell type

To investigate the mechanism of cell death induced by the N-alkylated prodigiosin analogue, 2,2'-[3-methoxy-1'amyl-5'-methyl-4-(1''-pyrryl)] dipyrryl-methene (MAMPDM) in S-180 and EL-4 tumour cell lines. Effect of MAMPDM on cell viability was assessed by MTT dye conversion. Induction of apoptosis was assessed by monitoring caspase 3 activity using a fluorogenic substrate, fragmentation of DNA by gel electrophoresis and sub-diploid DNA containing cells by flowcytometry. Necrosis was estimated by flowcytometric analysis of the uptake of propidium iodide. MAMPDM inhibited the proliferation of murine fibrosarcoma, S-180 cells and induced cell death. Investigations into the mechanism of cell death by MAMPDM in S-180 cells showed absence of hallmarks of apoptotic cell death such as activation of caspase 3, DNA fragmentation and presence of cells with sub-diploid DNA content. However, there was a rapid loss of membrane integrity as assessed by uptake of propidium iodide, which is characteristic of necrosis. In contrast to induction of necrosis in S-180 cells, MAMPDM induced apoptotic cell death in EL-4 cells as evident by activation of caspase 3, fragmentation of DNA and sub-diploid DNA containing cells. MAMPDM could induce cell death by either apoptosis or necrosis depending upon the cell type. This would be of advantage in elimination of tumor cells defective in apoptotic pathway and therefore, refractory to the conventional therapies.

Identification of a red-pigmented bacterium producing a potent anti-tumor N-alkylated prodigiosin as Serratia marcescens

A bacterial strain producing a novel prodigiosin analogue 2,2′-[3-methoxy-1′amyl-5′-methyl-4-(1″-pyrryl)] dipyrrylmethene (MAMPDM) possessing potent cytotoxic activity towards cancer cells was isolated and identified. The bacterial cells were spherical and occurred singly, and some of the biochemical tests matched with Micrococcus. Therefore, the isolate was earlier tentatively reported to be Micrococcus sp. In the present studies, analytical profile index (API) suggested this organism to be Klebsiella. However, Klebsiella is not known to produce the red pigment prodigiosin, which is produced by Serratia species and some other bacteria. Based on other biochemical characteristics, particularly DNase, gelatinase, lipase, ornithine decarboxylase, presence of a cell-associated N-alkylated prodigiosin (MAMPDM) and organic solvent tolerance, the strain has now been identified as a variant of Serratia marcescens. 16S rRNA gene analysis conclusively established this organism as S. marcescens ost3. The red pigment (MAMPDM) of this organism showed selective cytotoxic activity in cancer cell lines of different origin (LS-A and U937) and reduced toxicity to non-malignant cells. The LC 50 of MAMPDM was 1.59 μM and 0.176 μM for U937 and LS-A cells, respectively, while there was no effect on the viability of L929, a non-malignant cell line, at these concentrations. Thus, S. marcescens ost3 may serve as a source of a new anti-cancer compound.

Synthesis and Anti-Cancer Activity of C-Ring-Functionalized Prodigiosin Analogues

Prodigiosin is the parent member of the 4-methoxypyrrolyldipyrromethene family of natural products and is known for its anti-cancer activity. A new series of analogues was synthesized, incorporating pendent functional esters and beta-carbonyl substituents on the C-ring. The beta-carbonyl group allowed for the facile isolation of the prodigiosenes, and the pendent esters allow for further derivatization. The novel prodigiosenes generally retain the anti-cancer activity of prodigiosin in 60 human cell lines derived from nine cancer cell types, with neither the conjugated beta-carbonyl group, as either ketone or ester, nor the pendent ester significantly reducing the anti-cancer activity of the core skeleton.

Photo-Induced Cytotoxicity of Prodigiosin Analogues

Prodigiosin (1) is the parent member of a class of polypyrrole natural products that exhibit promising anticancer activities. They can facilitate copper-promoted oxidative DNA damage by binding to copper ions, and this activity is thought to represent their mechanism of cytotoxicity in the dark. They also possess photoinduced cytotoxicity, although 1 is too toxic in the dark to be used effectively for the treatment of cancer by photodynamic therapies. To circumvent dark toxicity by prodigiosins, the semi-synthetic analogue 2, in which the N-pyrrolic atoms of 1 are methylated to block copper coordination, and the synthetic phenyl analogues 3 and 4, which lack the copper-coordinating A-pyrrole ring of 1, were tested for their ability to inhibit colony formation of HL-60 cancer cells in the absence and presence of visible light (λ > 495 nm). Our results show that 2-4 lack cytotoxicity in the dark, but are able to inhibit colony formation of HL-60 cells following irradiation for 30 min. The synthetic derivative 4 exhibits photo-induced cytotoxicity similar to that of the natural product 1, demonstrating the potential use of prodigiosin-based compounds for treatment of cancers following irradiation with visible light.

4-Alkoxy- and 4-Amino-2,2‘-bipyrrole Synthesis

[Structure: see text] 4-alkoxy-2,2'-bipyrroles and the first examples of 4-amino-2,2'-bipyrroles have been synthesized by a diversity-oriented strategy from 4-hydroxyproline. The bipyrrole products offer interesting potential as building blocks for making pyrrole products, as demonstrated by the first synthesis of an amino prodigiosin analogue.

Biosynthesis of antibiotic prodiginines in the marine bacterium Hahella chejuensis KCTC 2396

Hahella chejuensis KCTC 2396 produces red pigments, showing antibacterial and algicidal activities. The main red-coloured metabolite of the pigments was identified as antibiotic prodigiosin. With the expectation that the red pigments are a mixture of a series of close relatives, the aim of the present study is to detect new antibiotic prodigiosin analogues and to analyse the biosynthetic pattern for prodiginines in KCTC 2396. Except prodigiosin, the other constituents in the red pigments were confirmed as well-known dipyrrolyldipyrromethene prodigiosin, norprodigiosin, and undecylprodiginine. Additionally, four new prodigiosin analogues, each of which was distinguished from prodigiosin (C(5)), according to differences in alkyl chain length (C(3)-C(7)), were detected in small quantities by liquid chromatography mass spectrometry/mass spectrometry spectroscopy. Owing to the presence of a cytotoxic methoxy group, it is expected that all the new prodigiosin analogues are bioactive. Four characterized prodiginines, including prodigiosin and four new prodigiosin analogues are produced in different ratio in KCTC 2396. All of the prodiginines possess a common linear tripyrrolyl structure and a cytotoxic methoxy group. This study shows for the first time that KCTC 2396 is able to produce antibiotic prodigiosin, undecylprodiginine and new prodigiosin analogues in a mixture of pigments. It is also shown that KCTC 2396 possesses a novel system for the simultaneous production of multiple prodiginines in a single micro-organism.

Photoinduced Cytotoxicity and Thioadduct Formation by a Prodigiosin Analogue

[reaction: see text] The prodigiosin alkaloid 1 and the synthetic analogue 2 show photoinduced cytotoxicity against HL-60 cancer cells. Photoirradiation of 1 and 2 causes photofading, photooxidation, and thioadduct formation. These results provide a model for the redox properties of prodigiosins that play a role in their biological activity and provide a new way to functionalize their pyrromethene entity with water-soluble thiol groups.