A Review of Phototoxic Plants, Their Phototoxic Metabolites, and Possible Developments as Photosensitizers.

This study provides a comprehensive overview of the current knowledge regarding phototoxic terrestrial plants and their phototoxic and photosensitizing metabolites. Within the 435,000 land plant species, only around 250 vascular plants have been documented as phototoxic or implicated in phototoxic occurrences in humans and animals. This work compiles a comprehensive catalog of these phototoxic plant species, organized alphabetically based on their taxonomic family. The dataset encompasses meticulous details including taxonomy, geographical distribution, vernacular names, and information on the nature and structure of their phototoxic and photosensitizing molecule(s). Subsequently, this study undertook an in-depth investigation into phototoxic molecules, resulting in the compilation of a comprehensive and up-to-date list of phytochemicals exhibiting phototoxic or photosensitizing activity synthesized by terrestrial plants. For each identified molecule, an extensive review was conducted, encompassing discussions on its phototoxic activity, chemical family, occurrence in plant families or species, distribution within different plant tissues and organs, as well as the biogeographical locations of the producer species worldwide. The analysis also includes a thorough discussion on the potential use of these molecules for the development of new photosensitizers that could be used in topical or injectable formulations for antimicrobial and anticancer phototherapy as well as manufacturing of photoactive devices.

Bisphosphonylallenes as Suitable Scaffolds for Unprecedented 4,5-Diphosphonyldihydropyridazines and 3,4-Diphosphonylpyrroles Displaying Antimelanoma Activity.

An efficient and simple approach has been developed for the synthesis of unprecedented 4,5-diphosphonyldihydropyridazines and 3,4-diphosphonylpyrroles, through the condensation of bisphosphonylallenes with hydrazines and primary amines, respectively. The reactions proceed under operationally simple, mild, and catalyst-free conditions, for a wide substrate scope. The synthesized compounds were screened for their antiproliferative activity against melanoma cancer cells, and they showed promising growth inhibition.

Archaea Carotenoids: Natural Pigments with Unexplored Innovative Potential.

For more than 40 years, marine microorganisms have raised great interest because of their major ecological function and their numerous applications for biotechnology and pharmacology. Particularly, Archaea represent a resource of great potential for the identification of new metabolites because of their adaptation to extreme environmental conditions and their original metabolic pathways, allowing the synthesis of unique biomolecules. Studies on archaeal carotenoids are still relatively scarce and only a few works have focused on their industrial scale production and their biotechnological and pharmacological properties, while the societal demand for these bioactive pigments is growing. This article aims to provide a comprehensive review of the current knowledge on carotenoid metabolism in Archaea and the potential applications of these pigments in biotechnology and medicine. After reviewing the ecology and classification of these microorganisms, as well as their unique cellular and biochemical characteristics, this paper highlights the most recent data concerning carotenoid metabolism in Archaea, the biological properties of these pigments, and biotechnological considerations for their production at industrial scale.

Alterins, a new family of marine antibacterial cyclolipopeptides.

Five strains of Pseudoalteromonas, isolated from oyster haemolymph, have exhibited antibacterial activity against several Gram-negative bacteria. Bioactive compounds have been identified in their cell-free supernatant and characterised as alterins, which are cyclolipopeptides comprising a heptapeptidic ring connected to a fatty acid chain. Using ultra-performance liquid chromatography-high-resolution mass spectrometry, this paper describes 37 structural analogues differing from each other by one or more amino acid residue, the length of the fatty acid chain, its hydroxylation and the presence of unsaturation.

Functionalization of 9-thioxanthone at the 1-position: From arylamino derivatives to [1]benzo(thio)pyrano[4,3,2-de]benzothieno[2,3-b]quinolines of biological interest.

Original 1-amino substituted thioxanthone derivatives were easily prepared from the bare heterocycle by a deprotometalation-iodolysis-copper-catalyzed CN bond formation sequence. This last reaction delivered mono- or/and diarylated products depending on the aniline involved. 1-Amino-9-thioxanthone was also prepared and reacted with 2-iodoheterocycles. Interestingly, while 1-(arylamino)-9-thioxanthones could be isolated, their subsequent cyclization was found to deliver original hexacyclic derivatives of helicoidal nature. Evaluation of their photophysical properties revealed high fluorescence in polar media, indicating potential applications for biological imaging. These compounds being able to inhibit PIM1 kinase, their putative binding mode was examined through molecular modeling experiments. Altogether, these results tend to suggest the discovery of a new family of fluorescent PIM inhibitors and pave the way for their future rational optimization.

Complete Genome Sequence of the Polymyxin E (Colistin)-Producing Paenibacillus sp. Strain B-LR.

Paenibacillus bacteria are recovered from varied niches, including human lung, rhizosphere, marine sediments, and hemolymph. Paenibacilli can have plant growth-promoting activities and be antibiotic producers. They can produce exopolysaccharides and enzymes of industrial interest. Illumina and PacBio reads were used to produce a complete genome sequence of the colistin producer Paenibacillus sp. strain B-LR.

From Quinoxaline, Pyrido[2,3-b]pyrazine and Pyrido[3,4-b]pyrazine to Pyrazino-Fused Carbazoles and Carbolines.

2,3-Diphenylated quinoxaline, pyrido[2,3-b]pyrazine and 8-bromopyrido[3,4-b]pyrazine were halogenated in deprotometalation-trapping reactions using mixed 2,2,6,6-tetramethyl piperidino-based lithium-zinc combinations in tetrahydrofuran. The 2,3-diphenylated 5-iodo- quinoxaline, 8-iodopyrido[2,3-b]pyrazine and 8-bromo-7-iodopyrido[3,4-b]pyrazine thus obtained were subjected to palladium-catalyzed couplings with arylboronic acids or anilines, and possible subsequent cyclizations to afford the corresponding pyrazino[2,3-a]carbazole, pyrazino[2',3':5,6] pyrido[4,3-b]indole and pyrazino[2',3':4,5]pyrido[2,3-d]indole, respectively. 8-Iodopyrido[2,3-b] pyrazine was subjected either to a copper-catalyzed C-N bond formation with azoles, or to direct substitution to introduce alkylamino, benzylamino, hydrazine and aryloxy groups at the 8 position. The 8-hydrazino product was converted into aryl hydrazones. Most of the compounds were evaluated for their biological properties (antiproliferative activity in A2058 melanoma cells and disease-relevant kinase inhibition).

Zeaxanthin from Porphyridium purpureum induces apoptosis in human melanoma cells expressing the oncogenic BRAF V600E mutation and sensitizes them to the BRAF inhibitor vemurafenib

Abstract Zeaxanthin, an abundant carotenoid present in fruits, vegetables and algae was reported to exert antiproliferative activity and induce apoptosis in human uveal melanoma cells. It also inhibited uveal melanoma tumor growth and cell migration in nude mice xenograft models. Here we report that zeaxanthin purified from the rhodophyte Porphyridium purpureum (Bory) K.M.Drew & R.Ross, Porphyridiaceae, promotes apoptosis in the A2058 human melanoma cell line expressing the oncogenic BRAF V600E mutation. Zeaxanthin 40 µM (IC50) induced chromatin condensation, nuclear blebbing, hypodiploidy, accumulation of cells in sub-G1 phase, DNA internucleosomal fragmentation and activation of caspase-3. Western blot analysis revealed that zeaxanthin induced up-regulation of the pro-apoptotic factors Bim and Bid and inhibition of NF-κB transactivation. Additionally, zeaxanthin sensitized A2058 melanoma cells in vitro to the cytotoxic activity of vemurafenib, a BRAF inhibitor widely used for the clinical management of melanoma, suggesting its potential interest as dietary adjuvant increasing melanoma cells sensitivity to chemotherapy.

Synthesis of 2-Mercapto-(2-Oxoindolin-3-Ylidene)Acetonitriles from 3-(4-Chloro-5H-1,2,3-Dithiazol-5-Ylidene)Indolin-2-ones.

Alkylidene oxindoles are important functional moieties and building blocks in pharmaceutical and synthetic chemistry. Our interest in biologically active compounds focused our studies on the synthesis of novel oxindoles, bearing on the exocyclic double bond at the C8, CN, and S groups. Extending the potential applications of Appel's salt, we developed a new synthetic approach by investigating the reactions of C5-substituted 2-oxindoles with 4,5-dichloro-1,2,3-dithiazolium chloride (Appel's salt) to give original (Z)-3-(4-chloro-5H-1,2,3-dithiazol-5-ylidene)indolin-2-one derivatives, and new 2-mercapto-(2-oxoindolin-3-ylidene)acetonitriles via a dithiazole ring-opening reaction. The work described in this article represents further applications of Appel's salt in the conception of novel heterocyclic rings, in an effort to access original bioactive compounds. Fifteen new compounds were prepared and fully characterized.

Sensitization of tumor cells to chemotherapy by natural products: A systematic review of preclinical data and molecular mechanisms.

PURPOSE: Tumor cells are spontaneously or adaptively resistant to chemotherapeutic drugs, eventually leading to the selection of multiresistant cells responsible for tumor growth and metastasis. Chemosensitization of tumor cells to conventional drugs using non-toxic natural products is a recent and innovative strategy aiming to increase the cytotoxic efficiency of anticancer drugs, limit their toxic side effects and delay the appearance of acquired chemoresistance. This systematic review summarizes data obtained from preclinical studies reporting the use of natural products to sensitize tumor cells to chemotherapeutic agents. It also details the cellular and molecular mechanisms involved in chemosensitization. DESIGN: Search terms were combined and used to retrieve English language reports in PubMed, Science Direct and Scopus databases, published until October 2017. All articles were carefully analyzed and data extraction was conducted through standardized forms. Methodological quality assessment of in vivo studies was also performed. RESULTS: From a total of 669 articles surveyed, 104 met the inclusion criteria established. The main studied compounds as chemosensitizers were phenolic derivatives (26.9%) and flavonoids (17.3%). Most reports were authored by researchers from China (33.7%) and USA (26.9%). A large number of articles were published from 2011 to 2015 (50.0%), suggesting that the use of natural products as chemosensitizers is a recent issue. In vivo studies were conducted mainly using xenograft models, which were considered of moderate methodological quality. CONCLUSION: Several natural products, belonging to diverse chemical families, are potent chemosentisizers in tumor cells enhancing the cytotoxicity of conventional drugs. These molecules usually have a pleiotropic effect on different molecular targets, acting on several cellular and molecular processes with low selectivity. All studied molecules were obtained from terrestrial plants and major developments should arise from future studies, considering the chemodiversity of molecules purified from other terrestrial taxa and marine organisms.

Improved racemate resolution of pentan-2-ol and trans-(Z)-cyclooct-5-ene-1,2-diol by lipase catalysis.

Lipases are important catalysts in chiral synthesis due to their wide substrate recognition combined with a high stereoselectivity. We demonstrate here that the state, free or immobilized, of Candida antarctica lipase B (CaLB) affects enantioselectivity and also alters the temperature dependancy of the enzyme. This indicates that CaLB undergoes various conformations induced by its interaction with the different immobilization supports studied. Molecular imprinting experiments, using immobilized enzyme co-dried with mimic substrate molecules, enhanced the enantiomeric ratio two-fold or three-fold, depending on the immobilization support. The structure of the acyl donor has a pronounced effect on CaLB catalyzed resolution, due to the proximity of the acyl and alcohol moieties during catalysis. When the acylation of pentan-2-ol was examined, we found that the 3C methyl propanoate donor afforded the highest resolution. Trans-(Z)-cyclooct-5-en-1,2-diol was used as a model racemic substrate to study the ability of lipase to catalyze the resolution of difunctionalized compounds. There was a clear enhancement in the enantiomer selectivity of the biotransformation of the diol when vinyl butanoate is used as the acyl donor. The conversion and enantiomeric excess of (1R,2R)-monoacetates were enhanced, using immobilized CaLB, when the chain length of the donors increased from C2 to C4.

Deproto-metallation of N-arylated pyrroles and indoles using a mixed lithium-zinc base and regioselectivity-computed CH acidity relationship.

The synthesis of N-arylated pyrroles and indoles is documented, as well as their functionalization by deprotonative metallation using the base in situ prepared from LiTMP and ZnCl2·TMEDA (1/3 equiv). With N-phenylpyrrole and -indole, the reactions were carried out in hexane containing TMEDA which regioselectively afforded the 2-iodo derivatives after subsequent iodolysis. With pyrroles and indoles bearing N-substituents such as 2-thienyl, 3-pyridyl, 4-methoxyphenyl and 4-bromophenyl, the reactions all took place on the substituent, at the position either adjacent to the heteroatom (S, N) or ortho to the heteroatom-containing substituent (OMe, Br). The CH acidities of the substrates were determined in THF solution using the DFT B3LYP method in order to rationalize the experimental results.

UPLC-MSE profiling of Phytoplankton metabolites: application to the identification of pigments and structural analysis of metabolites in Porphyridium purpureum.

A fast and high-resolution UPLC-MSE analysis was used to identify phytoplankton pigments in an ethanol extract of Porphyridium purpureum (Pp) devoid of phycobiliproteins. In a first step, 22 standard pigments were analyzed by UPLC-MSE to build a database including retention time and accurate masses of parent and fragment ions. Using this database, seven pigments or derivatives previously reported in Pp were unequivocally identified: ß,ß-carotene, chlorophyll a, zeaxanthin, chlorophyllide a, pheophorbide a, pheophytin a, and cryptoxanthin. Minor amounts of Divinyl chlorophyll a, a chemotaxonomic pigment marker for prochlorophytes, were also unequivocally identified using the database. Additional analysis of ionization and fragmentation patterns indicated the presence of ions that could correspond to hydroxylated derivatives of chlorophyll a and pheophytin a, produced during the ethanolic extraction, as well as previously described galactosyldiacylglycerols, the thylakoid coenzyme plastoquinone, and gracilamide B, a molecule previously reported in the red seaweed Gracillaria asiatica. These data point to UPLC-MSE as an efficient technique to identify phytoplankton pigments for which standards are available, and demonstrate its major interest as a complementary method for the structural elucidation of ionizable marine molecules.

Characterization of the colistin (polymyxin E1 and E2) biosynthetic gene cluster.

Colistin is a mixture of polymyxin E1 and E2, bactericidal pentacationic lipopeptides used to treat infections caused by Gram-negative pathogens such as Pseudomonas aeruginosa and Klebsiella pneumoniae. Industrial production of colistin is obtained by a fermentation process of the natural producer Paenibacillus polymyxa var colistinus. NonRibosomal peptide synthetases (NRPS) coding the biosynthesis of polymyxins A, B and P have been recently described, rendering thereof the improvement of their production possible. However, the colistin biosynthesis pathway was not published so far. In this study, a Paenibacillus alvei has been identified by biochemical (Api 50 CH system) and molecular (16S rDNA sequencing) methods. Its culture supernatant displayed inhibitory activity against Gram-negative bacteria (P. aeruginosa, K. pneumoniae, Salmonella spp.). Two polymyxins, E1 and E2, were recovered from the supernatant and were characterized by high resolution LC-MS. A genomic library (960 clones) was constructed to identify the gene cluster responsible for biosynthesis of polymyxins. Selection of the clones harbouring the sequences of interest was obtained by a simple PCR-based screening. We used primers targeting NRPS sequences leading to the incorporation of amino acids present in polymyxins E. The sequences from three clones of interest were assembled on 50.4 kb. Thus, five open reading frames corresponding to a new NRPS gene cluster of 41 kb were identified. In silico, analyses revealed the presence of three NRPS implicated in the biosynthesis of polymyxins E. This work provides insightful information on colistin biosynthesis and might contribute to future drug developments in this group of antibiotics.

Microwave-assisted extraction of phycobiliproteins from Porphyridium purpureum.

In the present study, microwave-assisted extraction was first employed to extract the phycobiliproteins of Porphyridium purpureum (Pp). Freeze-dried Pp cells were subjected to microwave-assisted extraction (MAE) to extract phycoerythin (PE), phycocyanin (PC), and allophycocyanin (APC). MAE combined reproducibility and high extraction yields and allowed a 180- to 1,080-fold reduction of the extraction time compared to a conventional soaking process. The maximal PE extraction yield was obtained after 10-s MAE at 40 °C, and PE was thermally damaged at temperatures higher than 40 °C. In contrast, a flash irradiation for 10 s at 100 °C was the best process to efficiently extract PC and APC, as it combined a high temperature necessary to extract them from the thylakoid membrane to a short exposure to thermal denaturation. The extraction order of the three phycobiliproteins was coherent with the structure of Pp phycobilisomes. Moreover, the absorption and fluorescence properties of MAE extracted phycobiliproteins were stable for several months after the microwave treatment. Scanning electron microscopy indicated that MAE at 100 °C induced major changes in the Pp cell morphology, including fusion of the exopolysaccharidic cell walls and cytoplasmic membranes of adjacent cells. As a conclusion, MAE is a fast and high yield process efficient to extract and pre-purify phycobiliproteins, even from microalgae containing a thick exopolysaccharidic cell wall.

Novel nonribosomal peptide synthetase (NRPS) genes sequenced from intertidal mudflat bacteria.

Nonribosomal peptide synthetases (NRPS) are actively sought out, due to pharmacologically important activities of their metabolites. In marine environment, the most prevalent nonribosomal peptide antibiotic producers are sponges inhabiting microorganisms. Conversely, strains from marine sediments and more especially from intertidal mudflats have not been extensively screened for the presence of new NRPS. In this study, for the first time, a collection of one hundred intertidal mudflat bacterial isolates (Marennes-Oléron Bay, France) was assessed for (1) the presence of NRPS genes by degenerated PCR targeting conserved adenylation domains and (2) for their production of antimicrobial molecules. (1) Bacteria with adenylation domains (14 strains) were identified by 16S rRNA gene sequence analysis and grouped into Firmicutes (one strain) and Proteobacteria (13 strains). In silico analysis of the NRPS amino acid sequences (n = 7) showed 41-58% ID with sequences found in the NCBI database. Three new putative adenylation domain signatures were found. (2) The culture supernatant of one of these strains, identified as a Bacillus, was shown to strongly inhibit the growth of Staphylococcus aureus, S. epidermidis, and Enterococcus faecalis. This study portends that the intertidal mudflat niche could be of interest for the discovery of new NRPS genes and antimicrobial producing strains.

Microwave-assisted kinetic resolution of homochiral (Z)-cyclooct-5-ene-1,2-diol and (Z)-2-acetoxycyclooct-4-enyl acetate using lipases.

Over the last decade, the use of biocatalysts has become an attractive alternative to conventional chemical methods, especially for organic synthesis, due to their unusual properties. Among these enzymes, lipases are the most widely used, because they are cheap, easily available, cofactor-free, and have broad substrate specificity. Combined to microwave heating in non-aqueous medium, recent results suggest that irradiation may influence the enzyme activity. This Communication reports the benefits of lipases and the microwave irradiation on the kinetic resolution of racemic homochiral (Z)-cyclooct-5-ene-1,2-diol and (Z)-2-acetoxycyclooct-4-enyl acetate. In order to best achieve the kinetic resolution, different parameters were studied including the type of lipase, the temperature, the impact of microwave power compared to conventional heating. Optimization of the reaction parameters lead to the obtainment of highly enriched or enantiopure diols and diesters in a clean, efficient and safe way.

Synthesis of C,N'-linked bis-heterocycles using a deprotometalation-iodination-N-arylation sequence and evaluation of their antiproliferative activity in melanoma cells.

Benzothiophene, benzofuran, benzothiazole and benzoxazole were deprotometalated using the lithium-zinc combination prepared from ZnCl2·TMEDA (TMEDA=N,N,N',N'-tetramethylethylenediamine, 1equiv) and lithium 2,2,6,6-tetramethylpiperidide (LiTMP, 3equiv). Subsequent interception of the 2-metalated derivatives using iodine as electrophile led to the iodides in 81%, 82%, 67% and 42% yields, respectively. These yields are higher (10% more) than those obtained using ZnCl2·TMEDA (0.5equiv) and LiTMP (1.5equiv), except in the case of benzoxazole (10% less). The crude iodides were involved in the N-arylation of pyrrole, indole, carbazole, pyrazole, indazole, imidazole and benzimidazole in the presence of Cu (0.2equiv) and Cs2CO3 (2equiv), and using acetonitrile as solvent (no other ligand) to provide after 24h reflux the expected N-arylated azoles in yields ranging from 33% to 81%. Using benzotriazole also led to N-arylation products, but in lower 34%, 39%, 36% and 6% yields, respectively. A further study with this azole evidenced the impact of 2,2,6,6-tetramethylpiperidine on the N-arylation yields. Most of the C,N'-linked bis-heterocycles thus synthesized (in particular those containing benzimidazole) induced a high growth inhibition of A2058 melanoma cells after a 72h treatment at 10(-5)M.

Antiproliferative activity of Cyanophora paradoxa pigments in melanoma, breast and lung cancer cells.

The glaucophyte Cyanophora paradoxa (Cp) was chemically investigated to identify pigments efficiently inhibiting malignant melanoma, mammary carcinoma and lung adenocarcinoma cells growth. Cp water and ethanol extracts significantly inhibited the growth of the three cancer cell lines in vitro, at 100 µg · mL(-1). Flash chromatography of the Cp ethanol extract, devoid of c-phycocyanin and allophycocyanin, enabled the collection of eight fractions, four of which strongly inhibited cancer cells growth at 100 µg · mL(-1). Particularly, two fractions inhibited more than 90% of the melanoma cells growth, one inducing apoptosis in the three cancer cells lines. The detailed analysis of Cp pigment composition resulted in the discrimination of 17 molecules, ten of which were unequivocally identified by high resolution mass spectrometry. Pheophorbide a, ß-cryptoxanthin and zeaxanthin were the three main pigments or derivatives responsible for the strong cytotoxicity of Cp fractions in cancer cells. These data point to Cyanophora paradoxa as a new microalgal source to purify potent anticancer pigments, and demonstrate for the first time the strong antiproliferative activity of zeaxanthin and ß-cryptoxanthin in melanoma cells.

Measuring angiotensin-I converting enzyme inhibitory activity by micro plate assays: comparison using marine cryptides and tentative threshold determinations with captopril and losartan.

To determine the angiotensin-I converting enzyme (ACE) inhibitory activity of marine cryptides, different methods were tested. ACE inhibition was measured using two synthetic substrates, (N-[3-(2-furyl) acryloyl]-Phe-Gly-Gly (FAPGG) and N-hippuryl-His-Leu hydrate salt (HHL)), and a natural one, angiotensin-I. The IC50 value (defined as the concentration of inhibitory molecule needed to inhibit 50% of the ACE activity) of the reference synthetic inhibitor captopril was in the nanomolar range (1.79-15.1 nM) when synthetic substrates were used, whereas it exhibited IC50 of micromolar range (16.71 µM) with angiotensin-I. We chose losartan, an antagonist of angiotensin-II receptor as negative control for the ACE inhibition. Losartan was also able to inhibit ACE whatever the substrate tested, with IC50 of micromolar range (17.13-146 µM). We defined this value as a limit above which molecules are not showing in vitro ACE inhibitory activity. Val-Trp (VW), Val-Tyr (VY), Lys-Tyr (KY), Lys-Trp (KW), Ile-Tyr (IY), Ala-Pro (AP), Val-Ile-Tyr (VIY), Leu-Lys-Pro (LKP), Gly-Pro-Leu (GPL), Ala-Lys-Lys (AKK), and Val-Ala-Pro (VAP) were tested as inhibitors of ACE with synthetic and natural substrates. IC50 displayed were substrate-dependent. With FAPGG as substrate, IW, VAP, KY, IY, AP, AKK, and VIY show IC50 values over the IC50 value of losartan and should not be considered as inhibitors of ACE. VY, VW, KW, and LKP exhibited IC50 value lower than the IC50 value of losartan for all substrates tested and were thus considered as good candidates for effectively decreasing hypertension. It appears that the comparison of IC50 is not consistent when IC50 values are obtained with different substrates and different methods. In vitro ACE inhibitory activity assays should always include various ACE substrates and references such as captopril and a negative control to obtain data reliable to discriminate ACE inhibitory peptides.