New Haloterpenes from the Marine Red Alga Laurencia papillosa: Structure Elucidation and Biological Activity.

Analysis of the air-dried marine red alga Laurencia papillosa, collected near Ras-Bakr at the Suez gulf (Red Sea) in Egypt delivered five new halogenated terpene derivatives: aplysiolic acid (1), 7-acetyl-aplysiol (2), aplysiol-7-one (3), 11,14-dihydroaplysia-5,11,14,15-tetrol (5a), and a new maneonene derivative 6, named 5-epi-maneolactone. The chemical structures of these metabolites were characterized employing spectroscopic methods, and the relative and absolute configurations were determined by comparison of experimental and ab initio-calculated NMR, NOE, ECD, and ORD data, and by X-ray diffraction of 2 and 6. The antimicrobial activities of the crude extract and compounds 1-3, 5a and 6 were studied.

Mansouramycins E-G, Cytotoxic Isoquinolinequinones from Marine Streptomycetes.

Chemical investigation of the ethyl acetate extract from the marine-derived Streptomyces sp. isolate B1848 resulted in three new isoquinolinequinone derivatives, the mansouramycins E-G (1a-3a), in addition to the previously reported mansouramycins A (5) and D (6). Their structures were elucidated by computer-assisted interpretation of 1D and 2D NMR spectra, high-resolution mass spectrometry, and by comparison with related compounds. Cytotoxicity profiling of the mansouramycins in a panel of up to 36 tumor cell lines indicated a significant cytotoxicity and good tumor selectivity for mansouramycin F (2a), while the activity profile of E (1a) was less attractive.

Karamomycins A-C: 2-Naphthalen-2-yl-thiazoles from Nonomuraea endophytica.

Karamomycins A-C (2-4), the first natural 2-naphthalen-2-yl-thiazole derivatives, were isolated along with a plausible precursor molecule, 1-hydroxy-4-methoxy-2-naphthoic acid (1), uracil, 1-acetyl-ß-carboline, and actinomycin C2 from the culture broth of the terrestrial actinomycete strain GW58/450, identified as Nonomuraea endophytica. These compounds were characterized by analysis of their NMR and mass spectrometry (MS) data; the absolute configurations of 2 and 4 were determined by comparison of 13C NMR, NOESY, and circular dichroism (CD) spectra with density functional theory (DFT)-calculated data. In karamomycin C (4), the thiazole of 2 is connected to an unusual iminothiazolo[4,3- c][1,4]thiazepinone, for which we proposed a biosynthetic origin from two cysteine residues. It is closely related to ulbactin F; however, the heterocycle is enantiomeric to the latter and connected to phenol instead of 4-methoxy-1-naphthol. Karamomycins A (2) and C (4) were cytotoxic.

Carbazole-, Aspidofractinine-, and Aspidocarpamine-Type Alkaloids from Pleiocarpa pycnantha.

Three new alkaloids, janetinine (1a), pleiokomenine A (2), and huncaniterine B (3a), and 13 known compounds, pleiomutinine (3b), huncaniterine A (3c), 1-carbomethoxy-ß-carboline (4), evoxanthine (5), deformyltalbotine acid lactone (6), pleiocarpamine (7), N4-methyl-10-hydroxygeissoschizol (8), spegatrine (9), neosarpagine (10), aspidofractinine (11), N1-methylkopsinin (12), pleiocarpine (13), and N1-methylkopsinin- N4-oxide (14), were isolated from the stem bark of Pleiocarpa pycnantha. Janetinine (1a) is a carbazole alkaloid; in pleiokomenine A (2), two aspidofractinine-type alkaloids are bridged by a methylene unit in an unprecedented way, and huncaniterine B (3a) is a pleiocarpamine-aspidofractinine-type dimer. The structures and relative configurations of these compounds were elucidated on the basis of NMR and MS analyses. Their absolute configurations were defined by means of experimental and calculated ECD data, and additionally, the structures of 5 and 13 were determined by single crystal X-ray diffraction. Compounds 1a, 2, 3b, 4, 6, 9, and 12 displayed cancer chemopreventive properties through either quinone reductase induction ( CD = 30.7, 30.2, 29.9, 43.5, and 36.7 µM for 1a, 4, 6, 9, and 12, respectively) and/or NF-κB inhibition with IC50 values of 13.1, 8.4, 9.4, and 8.8 µM for 2, 3b, 6, and 12, respectively.

Epigenetic Modulation of Endophytic Eupenicillium sp. LG41 by a Histone Deacetylase Inhibitor for Production of Decalin-Containing Compounds.

An endophytic fungus, Eupenicillium sp. LG41, isolated from the Chinese medicinal plant Xanthium sibiricum, was subjected to epigenetic modulation using an NAD+-dependent histone deacetylase (HDAC) inhibitor, nicotinamide. Epigenetic stimulation of the endophyte led to enhanced production of two new decalin-containing compounds, eupenicinicols C and D (3 and 4), along with two biosynthetically related known compounds, eujavanicol A (1) and eupenicinicol A (2). The structures and stereochemistry of the new compounds were elucidated by extensive spectroscopic analysis using LC-HRMS, NMR, optical rotation, and ECD calculations, as well as single-crystal X-ray diffraction. Compounds 3 and 4 exist in chemical equilibrium with two and three cis/trans isomers, respectively, as revealed by LC-MS analysis. Compound 4 was active against Staphylococcus aureus with an MIC of 0.1 µg/mL and demonstrated marked cytotoxicity against the human acute monocytic leukemia cell line (THP-1). We have shown that the HDAC inhibitor, nicotinamide, enhanced the production of compounds 3 and 4 by endophytic Eupenicillium sp. LG41, facilitating their isolation, structure elucidation, and evaluation of their biological activities.

Metabolites from the Endophytic Fungus Curvularia sp. M12 Act as Motility Inhibitors against Phytophthora capsici Zoospores.

The endophytic fungus Curvularia sp., strain M12, was isolated from a leaf of the medicinal plant Murraya koenigii and cultured on rice medium followed by chemical screening of the culture extract. Chromatographic analysis led to the isolation of four new compounds, murranofuran A (1), murranolide A (2), murranopyrone (3a), and murranoic acid A (4a), along with six known metabolites, N-(2-hydroxy-6-methoxyphenyl)acetamide (5), curvularin (6), (S)-dehydrocurvularin (7), pyrenolide A (8), modiolide A (9), and 8-hydroxy-6-methoxy-3-methylisocoumarin (10). The structures of the known compounds were confirmed by comparing ESI HR mass spectra, 1H and 13C NMR, and optical rotation data with values reported in the literature. The planar structures of the new compounds were elucidated by extensive analysis of 1D and 2D NMR and mass data. The absolute configurations of the new compounds were established by coupling constant analysis, modified Mosher's method, and CD data. Compound 8 showed a strong motility impairing activity against Phytophthora capsici zoospores at a low concentration (100% at 0.5 µg/mL) in a short time (30 min). Compounds 2, 3a, 6, 7, 9, and 10 exhibited zoospore motility impairment activity at higher concentrations (IC50: 50-100 µg/mL).

Antibacterial Azaphilones from an Endophytic Fungus, Colletotrichum sp. BS4.

Three new compounds, colletotrichones A-C (1-3), and one known compound, chermesinone B (4a), were isolated from an endophytic fungus, Colletotrichum sp. BS4, harbored in the leaves of Buxus sinica, a well-known boxwood plant used in traditional Chinese medicine (TCM). Their structures were determined by extensive spectroscopic analyses including 1D and 2D NMR, HRMS, ECD spectra, UV, and IR, as well as single-crystal X-ray diffraction, and shown to be azaphilones sharing a 3,6a-dimethyl-9-(2-methylbutanoyl)-9H-furo[2,3-h]isochromene-6,8-dione scaffold. Owing to the remarkable antibacterial potency of known azaphilones coupled to the usage of the host plant in TCM, we evaluated the antibacterial efficacy of the isolated compounds against two commonly dispersed environmental strains of Escherichia coli and Bacillus subtilis, as well as against two human pathogenic clinical strains of Staphylococcus aureus and Pseudomonas aeruginosa. Compound 1 exhibited marked antibacterial potencies against the environmental strains that were comparable to the standard antibiotics. Compound 3 was also active against E. coli. Finally, compound 2a exhibited the same efficacy as streptomycin against the clinically relevant bacterium S. aureus. The in vitro cytotoxicity of these compounds on a human acute monocytic leukemia cell line (THP-1) was also assessed. Our results provide a scientific rationale for further investigations into endophyte-mediated host chemical defense against specialist and generalist pathogens.

Marine Bacteria, XLVII - Psychrotolerant Bacteria from Extreme Antarctic Habitats as Producers of Rare Bis- and Trisindole Alkaloids.

From the gastrointestinal tract of a fish dredged near the South Orkney Islands in Antarctica, we isolated the psychrotolerant bacterial strain T262, which belongs to the species Vibrio splendidus. Investigation of this strain led to the isolation of a series of 15 bis- and trisindole derivatives. Among them, six new indole alkaloids, namely, turbomycin C [4'-n-butoxyphenyl-bis(1H-indol-3-yl)methane, 1a], turbomycin D [4'-n-propoxyphenyl-bis(1H-indol-3-yl)methane, 1b], turbomycin E [4'-ethoxyphenyl-bis(1H-indol-3-yl)methane, 1c], turbomycin F [4'-methoxy-3',5'-dinitrophenyl-bis(1H-indol-3-yl)methane, 2], trisindolal (3a), and 4-(1H-indol-3-yl-sulfanyl)phenol (4). Another new bisindole derivative elucidated as 2-(indol-3-ylmethyl)-indol-3-ylethanol (7a) was obtained together with six known compounds from the psychrotolerant Arthrobacter psychrochitiniphilus strain T406, isolated from the excrement of penguins. Some of the isolated compounds showed activity against both gram-positive and gram-negative bacteria at 10 µg/paper disk. Trisindolal (3a) was active against the peronosporomycetes Botrytis cinerea and Phytophthora infestans, and some of the indole derivatives indicated promising cytotoxicity towards human tumor cell lines. By exhibiting a mean IC50 of 0.45 µg/mL (1.17 µM), trisindolal (3a) showed pronounced potency and selectivity in a panel of 11 human tumor cell lines derived from 10 different tumor histotypes.

Antibacterial secondary metabolites from an endophytic fungus, Eupenicillium sp. LG41.

Two new compounds containing the decalin moiety, eupenicinicols A and B (1 and 2), two new sirenin derivatives, eupenicisirenins A and B (3 and 4), and four known compounds, (2S)-butylitaconic acid (5), (2S)-hexylitaconic acid (6), xanthomegnin (7), and viridicatumtoxin (8), were isolated from an endophytic fungus, Eupenicillium sp. LG41, harbored in the roots of the Chinese medicinal plant Xanthium sibiricum. Their structures were confirmed through combined spectroscopic analysis (NMR and HRMS(n)), and their absolute configurations were deduced by ECD calculations or optical rotation data. Since the endophytic fungus was isolated from the roots, the antibacterial efficacies of the compounds 1-6 were investigated against Bacillus subtilis and Acinetobacter sp. BD4, which typically inhabit soil, as well as the clinically important Staphylococcus aureus and Escherichia coli. (2S)-Butylitaconic acid (5) and (2S)-hexylitaconic acid (6) exhibited pronounced efficacy against Acinetobacter sp., corroborating the notion that root-endophytes provide chemical defense to the host plants. Compound 2 was highly active against the clinically relevant S. aureus. By comparing 1 with 2, it was revealed that altering the substitution at C-11 could drastically increase the antibacterial efficacy of 1. Our study reveals plausible ecological roles of the endophyte and its potential pharmaceutical use as a source of antibacterial compounds.

Pachydictyols B and C: new diterpenes from Dictyota dichotoma Hudson.

Two new diterpenoids, pachydictyol B (1a/1b) and C (2), were isolated from the dichloromethane extract of the marine brown alga, Dictyota dichotoma, collected from the Red Sea coast of Egypt, along with the known metabolites, pachydictyol A (3a), dictyol E (4), cis-africanan-1α-ol (5a), fucosterol (6), tetrahydrothiophen-1,1-dioxide and poly-ß-hydroxybutyric acid. GC-MS analysis of the nonpolar fractions also indicated the presence of ß-bourbonene and nonanal, along with three hydrocarbons and five fatty acids or their simple derivatives, respectively. GC-MS analysis of the unsaponifiable algal petroleum ether extract revealed the presence of a further eight compounds, among them 2,2,6,7-tetramethyl-10-oxatricyclo[4.3.0.1(1,7)]decan-5-one (7), N-(4-bromo-n-butyl)-pipe ridin-2-one (8) and tert-hexadecanethiol. Structures 1-6 were assigned by 1D and 2D NMR, mass spectra (EI, CI, HREI and HRESI) and by comparison with data from related structures. The crude algal extract was potently active against the breast carcinoma tumor cell line, MCF7 (IC50 = 0.6 µg mL⁻¹); pachydictyol B (1a) and dictyol E (4) showed weak antimicrobial properties, and the other compounds were inactive. Pachydictyols B (1a) and C (2) demonstrated a weak and unselective cytotoxicity against twelve human tumor cell lines with a mean IC50 of >30.0 µM.

A new C-glucosylflavone from Sorindeia juglandifolia.

Phytochemical investigation of the leaves of Sorindeia juglandifolia A. Rich. led to the isolation and identification of a new C-glucosylflavone, 2",6"-di-O-acetyl-7-O-methyl vitexin (1), together with seven known compounds, 2"-O-acetyl-7-O-methyl vitexin (2), mearnsitrin (3), robustaflavone (4), 3-O-galloyl catechin (5), tachioside (2-methoxy-benzene-1,4-diol-1-O-beta-glucopyranoside) (6), 3beta-O-D-glucopyranosyl-beta-stigmasterol (7), and methyl gallate (8). The structures of 1 and the known compounds were established by IR, UV, MS, 1D, and 2D NMR spectra and by comparison with those of related compounds.

Sulochrins and alkaloids from a fennel endophyte Aspergillus sp. FVL2.

The fungal endophyte Aspergillus sp. strain FVL2, isolated from the traditional medicinal fennel plant, Foeniculum vulgare, was investigated for secondary metabolites. Fermentation on rice medium followed by chromatographic separation delivered three new natural products, 7-demethyl-neosulochrin (1), fumigaclavine I (3) and N-benzoyl-tryptophan (6) together with further 14 known metabolites, 1-O-methyl-sulochrin-4'-sulfate, questin, laccaic acid, isorhodoptilometrin, fumigaclavine A, fumigaclavine C, fumitremorgin C, fumigaquinazoline C, tryptoquivaline J, trypacidin, 3'-O-demethyl-sulochrin, 1-O-methyl-sulochrin, protocatechuic acid, and vermelone. The chemical structures of the new metabolites were determined by NMR spectroscopy and ESI HR mass spectrometry. For fumigaclavine I, we observed the partial deuterium transfer from the solvent to the enol form with a remarkable high stereo selectivity. The discovery of the new seco-anthraquinone 7-demethyl-neosulochrin (1) revealed a second type of ring cleavage by a questin oxygenase. The discovery of diverse secondary metabolites broadens the chemical space of Aspergillus.

Fusaroside, a unique glycolipid from Fusarium sp., an endophytic fungus isolated from Melia azedarach.

Fusaroside (1), a unique trehalose-containing glycolipid composed of the 4-hydroxyl group of a trehalose unit attached to the carboxylic carbon of a long-chain fatty acid, was isolated from the organic extract of fermentation broths of an endophytic fungus, Fusarium sp. LN-11 isolated from the leaves of Melia azedarach. Six known compounds, phalluside (2), (9R*,10R*,7E)-6, 9,10-trihydroxyoctadec-7-enoic acid (3), porrigenic acid (4), (9Z)-2,3-dihydroxypropyl octadeca-9-enoate (5), cerevisterol (6) and ergokonin B (7), were also isolated from this fungus. The glycolipid contains a rare branched long-chain fatty acid (C(20:4)) with a conjugated diene moiety and a conjugated ketone moiety. The structure of the new compound 1 was elucidated by spectroscopic methods (1D and 2D NMR experiments, MS) and chemical degradations. The metabolites 1-5 were shown to have moderate to weak active against the brine shrimp larvae. To our knowledge, this is the first report of isolation of the first representative of a new family of glycolipids from natural sources.

Persipeptides A and B, two cyclic peptides from Streptomyces sp. UTMC 1154.

Two new N-methylated cyclopeptides, persipeptide A (1) and B (2), have been isolated from Streptomyces sp. UTMC1154. Their structures were established using 1D and 2D NMR experiments. 2D TOCSY experiments were applied to identify the amino acid residues, while HMBC correlations were used to determine their sequence. According to Marfey's method, all amino acids had the l-configuration. The two cyclic peptides had the same ring size and amino acid composition, but differed in their sequence; they did not show activity against the tested bacteria, fungi and algae. Molecular identification experiments placed the strain in the genus Streptomyces closely related to Streptomyces coerulescens DSM40146(T) (99.45%) and Streptomyces varsoviensis DSM40346(T) (99.25%).

Chromophenazines from the terrestrial Streptomyces sp. Ank 315.

The new chromophenazines A-F [9-methyl-5-(3'-methylbut-2'-enyl)-5H-benzo[a]phenazin-7-one (1a), 9-methyl-5-(3'-methylbut-2'-enyl)-7-oxo-5,7-dihydrobenzo[a]phenazine-1-carboxylic acid (1b), 5-(3'-methylbut-2'-enyl)-7-oxo-5,7-dihydrophenazine-1-carboxamide (2), 3-benzoyl-5-(3'-methylbut-2'-enyl)-5,10-dihydrophenazine-1-carboxylic acid (5a), 3,7-dibenzoyl-5-(3'-methylbut-2'-enyl)-5,10-dihydrophenazine-1-carboxylic acid (5b), and 3,7-dibenzoyl-5-(3'-methylbut-2'-enyl)-5,10-dihydrophenazine-1-carboxamide (5c)], together with phenazine-1-carboxylic acid, 1-phenazinecarboxamide, 1-phenazinol, tryptophol, and anthranilic acid, were isolated from Streptomyces sp. Ank 315. The structures of the new compounds were established on the basis of spectroscopic data, 1D NOE, 2D NMR, and ESIMS measurements and comparison with literature values.

Absolute configuration of fusarone, a new azaphilone from the endophytic fungus Fusarium sp. isolated from Melia azedarach, and of related azaphilones.

A new azaphilone derivative, named fusarone (1), has been isolated from the ethyl acetate soluble extract of the fermentation broth of an endophytic fungus, Fusarium sp. LN-12, isolated from the leaves of Melia azedarach Linn. The structure of the new compound was established on the basis of extensive spectroscopic analysis, including 1D-NMR and 2D-NMR ((1) H-(1)H COSY, TOCSY, HSQC, HMBC, and NOESY) experiments. The absolute configurations of fusarone (1) and of a second related azaphilone were determined by means of electronic circular dichroism spectroscopy and optical rotation calculations.

Paeciloside A, a new antimicrobial and cytotoxic polyketide from Paecilomyces sp. strain CAFT156.

Paeciloside A (1) and eight known compounds, acremoauxin A (2), farinosones A (3) and B (4), 1,5-dideoxy-3-C-methyl-arabitol (5), ergosterol, ergosterol peroxide, cerebroside C, and adenosine, were isolated from cultures of Paecilomyces sp. CAFT156, an endophytic fungus occurring in Enantia chlorantha Oliv (Annonaceae) leaves. The structure of the new compound 1 was elucidated using MS, UV, 1D and 2D NMR experiments, while its absolute configuration was established by subsequent single-crystal X-ray diffraction analysis using copper Kα radiation and invariom nonspherical scattering factors. Paeciloside A (1) and compounds 2, 4, and 5 displayed inhibitory effects on two gram-positive bacteria, Bacillus subtilis and Staphylococcus aureus at a concentration of 40 µg per paper disk and moderate cytotoxicity towards brine shrimp larvae (Artemia salina). This study presents the first report on an endophytic fungus isolated from E. chlorantha Oliv and its natural products.

Cytotoxicity and antimicrobial activity of the methanol extract and compounds from Polygonum limbatum.

The present study was designed to investigate the antimicrobial activity and the cytotoxicity of the methanol extract (PLA) as well as fractions (PLA1-4) and compounds [cardamomin (1), (±)-polygohomoisoflavanone (2), (S)-(-)-pinostrobin (3), 2',4'-dihydroxy-3',6'-dimethoxychalcone (4), (2S)-(-)-5-hydroxy-6,7-dimethoxyflavanone (5), and (2S)-(-)-5,7-dimethoxyflavanone (6)] obtained from leaves of Polygonum limbatum. The microbroth dilution was used to determine the minimal inhibitory concentration (MIC) of the samples against 11 microbial strains including Candida albicans, C. krusei, C. tropicalis, Aspergillus fumigatus, Pseudomonas aeruginosa, Escherichia coli, vancomycin-resistant Enterococcus faecalis (VRE), Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), S.epidermidis, and Mycobacterium tuberculosis H37Rv. The sulphorhodamine B cell growth inhibition assay was used to assess the cytotoxicity of the above samples on lung A549 adenocarcinoma, breast carcinoma MCF-7, prostate carcinoma PC-3, cervical carcinoma HeLa, and the acute monocytic leukemia cell line THP-1. The results of the MIC determination indicated that, apart from fraction PLA3, all other fractions as well as PLA and compound 3 were selectively active. MIC values were noted on 100 % of the 11 tested microorganisms for fraction PLA3, 72.7 % for PLA, fraction PLA2, and compound 4, 63.6 % for PLA1, and 54.5 % for fraction PLA4. The results of the cytotoxicity assay revealed that, except for A459 cells, more than 50 % inhibition of the proliferation was obtained with each of the tested samples on at least one of the four other cell lines. IC50 values below 4 µg/mL were obtained with 1 and 4 on THP-1 cells. The overall results of the present study provided baseline information for the possible use of Polygonum limbatum as well as some of the isolated compounds for the control of cancer diseases and mostly leukemia.

Kiamycin, a unique cytotoxic angucyclinone derivative from a marine Streptomyces sp.

Kiamycin (1), a new angucyclinone derivative possessing an 1,12-epoxybenz[a]anthracene ring system, was isolated from the marine Streptomyces sp. strain M268 along with the known compounds 8-O-methyltetrangomycin (3) and 8-O-methylrabelomycin (4). Their structures were elucidated by detailed spectroscopic analysis and comparison with literature data. The new angucyclinone derivative showed inhibitory activities against the human cell lines HL-60 (leukemia), A549 (lung adenocarcinoma), and BEL-7402 (hepatoma) with inhibition rates of 68.2%, 55.9%, and 31.7%, respectively, at 100 µM. It appears to have potential as an anticancer agent with selective activity.