Robert H. Cichewicz

Find an error

Name: Cichewicz, Robert H.

Organization: University of Oklahoma , USA

Department: Department of Chemistry and Biochemistry

Title: (PhD)

TOPICS

Organic Chemistry

Chemicals
References

Chlorinated Polyketide Obtained from a Daldinia sp. Treated with the Epigenetic Modifier Suberoylanilide Hydroxamic Acid

Co-reporter:Lin Du, Jarrod B. King, and Robert H. Cichewicz

Journal of Natural Products November 26, 2014 Volume 77(Issue 11) pp:2454-2458

Publication Date(Web):October 22, 2014

DOI:10.1021/np500522z

A new chlorinated pentacyclic polyketide, daldinone E (1), was purified from a Daldinia sp. fungal isolate treated with the epigenetic modifier suberoylanilide hydroxamic acid (SAHA). A biosynthetically related epoxide-containing daldinone analogue, 2, was also purified from the same fungus. The structures of both compounds were established by spectroscopic methods, and the absolute configurations were assigned by analysis of their NMR data (coupling constants and ROESY correlations) and DFT calculations of specific rotations and ECD spectra. During the course of these studies it was determined that metabolite 2 and the previously reported daldinone B shared the same spectroscopic data, leading to a revision of the reported structure. Both compounds 1 and 2 also exhibited DPPH radical scavenging activities with potency comparable to the positive control ascorbic acid.

Opportunistic Sampling of Roadkill as an Entry Point to Accessing Natural Products Assembled by Bacteria Associated with Non-anthropoidal Mammalian Microbiomes

Co-reporter:Jeremy L. Motley, Blake W. Stamps, Carter A. Mitchell, Alec T. Thompson, Jayson Cross, Jianlan You, Douglas R. Powell, Bradley S. Stevenson, and Robert H. Cichewicz

Journal of Natural Products March 24, 2017 Volume 80(Issue 3) pp:598-598

Publication Date(Web):November 21, 2016

DOI:10.1021/acs.jnatprod.6b00772

Few secondary metabolites have been reported from mammalian microbiome bacteria despite the large numbers of diverse taxa that inhabit warm-blooded higher vertebrates. As a means to investigate natural products from these microorganisms, an opportunistic sampling protocol was developed, which focused on exploring bacteria isolated from roadkill mammals. This initiative was made possible through the establishment of a newly created discovery pipeline, which couples laser ablation electrospray ionization mass spectrometry (LAESIMS) with bioassay testing, to target biologically active metabolites from microbiome-associated bacteria. To illustrate this process, this report focuses on samples obtained from the ear of a roadkill opossum (Dideiphis virginiana) as the source of two bacterial isolates (Pseudomonas sp. and Serratia sp.) that produced several new and known cyclic lipodepsipeptides (viscosin and serrawettins, respectively). These natural products inhibited biofilm formation by the human pathogenic yeast Candida albicans at concentrations well below those required to inhibit yeast viability. Phylogenetic analysis of 16S rRNA gene sequence libraries revealed the presence of diverse microbial communities associated with different sites throughout the opossum carcass. A putative biosynthetic pathway responsible for the production of the new serrawettin analogues was identified by sequencing the genome of the Serratia sp. isolate. This study provides a functional roadmap to carrying out the systematic investigation of the genomic, microbiological, and chemical parameters related to the production of natural products made by bacteria associated with non-anthropoidal mammalian microbiomes. Discoveries emerging from these studies are anticipated to provide a working framework for efforts aimed at augmenting microbiomes to deliver beneficial natural products to a host.

Maximiscin Induces DNA Damage, Activates DNA Damage Response Pathways, and Has Selective Cytotoxic Activity against a Subtype of Triple-Negative Breast Cancer

Co-reporter:Andrew J. Robles; Lin Du; Robert H. Cichewicz;Susan L. Mooberry

Journal of Natural Products 2016 Volume 79(Issue 7) pp:1822-1827

Publication Date(Web):June 16, 2016

DOI:10.1021/acs.jnatprod.6b00290

Triple-negative breast cancers are highly aggressive, and patients with these types of tumors have poor long-term survival. These breast cancers do not express estrogen or progesterone receptors and do not have gene amplification of human epidermal growth factor receptor 2; therefore, they do not respond to available targeted therapies. The lack of targeted therapies for triple-negative breast cancers stems from their heterogeneous nature and lack of a clear definition of driver defects. Studies have recently identified triple-negative breast cancer molecular subtypes based on gene expression profiling and representative cell lines, allowing for the identification of subtype-specific drug leads and molecular targets. We previously reported the identification of a new fungal metabolite named maximiscin (1) identified through a crowdsourcing program. New results show that 1 has selective cytotoxic efficacy against basal-like 1 MDA-MB-468 cells compared to cell lines modeling other triple-negative breast cancer molecular subtypes. This compound also exhibited antitumor efficacy in a xenograft mouse model. The mechanisms of action of 1 in MDA-MB-468 cells were investigated to identify potential molecular targets and affected pathways. Compound 1 caused accumulation of cells in the G1 phase of the cell cycle, suggesting induction of DNA damage. Indeed, treatment with 1 caused DNA double-strand breaks with concomitant activation of the DNA damage response pathways, indicated by phosphorylation of p53, Chk1, and Chk2. Collectively, these results suggest basal-like triple-negative breast cancer may be inherently sensitive to DNA-damaging agents relative to other triple-negative breast cancer subtypes. These results also demonstrate the potential of our citizen crowdsourcing program to identify new lead molecules for treating the subtypes of triple-negative breast cancer.

Texas Native Plants Yield Compounds with Cytotoxic Activities against Prostate Cancer Cells

Co-reporter:Corena V. Shaffer; Shengxin Cai; Jiangnan Peng; Andrew J. Robles; Rachel M. Hartley; Douglas R. Powell; Lin Du; Robert H. Cichewicz;Susan L. Mooberry

Journal of Natural Products 2016 Volume 79(Issue 3) pp:531-540

Publication Date(Web):January 19, 2016

DOI:10.1021/acs.jnatprod.5b00908

There remains a critical need for more effective therapies for the treatment of late-stage and metastatic prostate cancers. Three Texas native plants yielded three new and three known compounds with antiproliferative and cytotoxic activities against prostate cancer cells with IC50 values in the range of 1.7–35.0 μM. A new sesquiterpene named espadalide (1), isolated from Gochnatia hypoleuca, had low micromolar potency and was highly effective in clonogenic assays. Two known bioactive germacranolides (2 and 3) were additionally isolated from G. hypoleuca. Dalea frutescens yielded two new isoprenylated chalcones, named sanjuanolide (4) and sanjoseolide (5), and the known sesquiterpenediol verbesindiol (6) was isolated from Verbesina virginica. Mechanistic studies showed that 1–4 caused G2/M accumulation and the formation of abnormal mitotic spindles. Tubulin polymerization assays revealed that 4 increased the initial rate of tubulin polymerization, but did not change total tubulin polymer levels, and 1–3 had no effects on tubulin polymerization. Despite its cytotoxic activity, compound 6 did not initiate changes in cell cycle distribution and has a mechanism of action different from the other compounds. This study demonstrates that new compounds with significant biological activities germane to unmet oncological needs can be isolated from Texas native plants.

Identification of Compounds with Efficacy against Malaria Parasites from Common North American Plants

Co-reporter:Shengxin Cai; April L. Risinger; Shalini Nair; Jiangnan Peng; Timothy J. C. Anderson; Lin Du; Douglas R. Powell; Susan L. Mooberry

Journal of Natural Products 2016 Volume 79(Issue 3) pp:490-498

Publication Date(Web):December 21, 2015

DOI:10.1021/acs.jnatprod.5b00874

Some of the most valuable antimalarial compounds, including quinine and artemisinin, originated from plants. While these drugs have served important roles over many years for the treatment of malaria, drug resistance has become a widespread problem. Therefore, a critical need exists to identify new compounds that have efficacy against drug-resistant malaria strains. In the current study, extracts prepared from plants readily obtained from local sources were screened for activity against Plasmodium falciparum. Bioassay-guided fractionation was used to identify 18 compounds from five plant species. These compounds included eight lupane triterpenes (1–8), four kaempferol 3-O-rhamnosides (10–13), four kaempferol 3-O-glucosides (14–17), and the known compounds amentoflavone and knipholone. These compounds were tested for their efficacy against multi-drug-resistant malaria parasites and counterscreened against HeLa cells to measure their antimalarial selectivity. Most notably, one of the new lupane triterpenes (3) isolated from the supercritical extract of Buxus sempervirens, the common boxwood, showed activity against both drug-sensitive and -resistant malaria strains at a concentration that was 75-fold more selective for the drug-resistant malaria parasites as compared to HeLa cells. This study demonstrates that new antimalarial compounds with efficacy against drug-resistant strains can be identified from native and introduced plant species in the United States, which traditionally have received scant investigation compared to more heavily explored tropical and semitropical botanical resources from around the world.

Chemoreactive Natural Products that Afford Resistance Against Disparate Antibiotics and Toxins

Co-reporter:Dr. Lin Du;Dr. Jianlan You;Dr. Kenneth M. Nicholas ;Dr. Robert H. Cichewicz

Angewandte Chemie 2016 Volume 128( Issue 13) pp:4292-4297

Publication Date(Web):

DOI:10.1002/ange.201511348

Abstract

Microorganisms use chemical inactivation strategies to circumvent toxicity caused by many types of antibiotics. Yet in all reported cases, this approach is limited to enzymatically facilitated mechanisms that each target narrow ranges of chemically related scaffolds. The fungus-derived shikimate analogues, pericoxide and pericosine A, were identified as chemoreactive natural products that attenuate the antagonistic effects of several synthetic and naturally derived antifungal agents. Experimental and computational studies suggest that pericoxide and pericosine A readily react via S_N2′ mechanisms against a variety of nucleophilic substances under both in vitro aqueous and in situ co-culture conditions. Many of the substitution products from this reaction were highly stable and exhibited diminished toxicities against environmental fungal isolates, including the Tolypocladium sp. strain that produced pericoxide and pericosine A.

Chemoreactive Natural Products that Afford Resistance Against Disparate Antibiotics and Toxins

Co-reporter:Dr. Lin Du;Dr. Jianlan You;Dr. Kenneth M. Nicholas ;Dr. Robert H. Cichewicz

Angewandte Chemie International Edition 2016 Volume 55( Issue 13) pp:4220-4225

Publication Date(Web):

DOI:10.1002/anie.201511348

Abstract

Selective activity of deguelin identifies therapeutic targets for androgen receptor-positive breast cancer

Co-reporter:Andrew J. Robles;Shengxin Cai;Robert H. Cichewicz;Susan L. Mooberry

Breast Cancer Research and Treatment 2016 Volume 157( Issue 3) pp:475-488

Publication Date(Web):2016/06/01

DOI:10.1007/s10549-016-3841-9

Triple-negative breast cancers (TNBC) are aggressive malignancies with no effective targeted therapies. Recent gene expression profiling of these heterogeneous cancers and the classification of cell line models now allows for the identification of compounds with selective activities against molecular subtypes of TNBC. The natural product deguelin was found to have selective activity against MDA-MB-453 and SUM-185PE cell lines, which both model the luminal androgen receptor (LAR) subtype of TNBC. Deguelin potently inhibited proliferation of these cells with GI50 values of 30 and 61 nM, in MDA-MB-453 and SUM-185PE cells, respectively. Deguelin had exceptionally high selectivity, 197 to 566-fold, for these cell lines compared to cell lines representing other TNBC subtypes. Deguelin’s mechanisms of action were investigated to determine how it produced these potent and selective effects. Our results show that deguelin has dual activities, inhibiting PI3K/Akt/mTOR signaling, and decreasing androgen receptor levels and nuclear localization. Based on these data, we hypothesized that the combination of the mTOR inhibitor rapamycin and the antiandrogen enzalutamide would have efficacy in LAR models. Rapamycin and enzalutamide showed additive effects in MDA-MB-453 cells, and both drugs had potent antitumor efficacy in a LAR xenograft model. These results suggest that the combination of antiandrogens and mTOR inhibitors might be an effective strategy for the treatment of androgen receptor-expressing TNBC.

Transferring Fungi to a Deuterium-Enriched Medium Results in Assorted, Conditional Changes in Secondary Metabolite Production

Co-reporter:Bin Wang; Elizabeth M. Park; Jarrod B. King; Allison O. Mattes; Susan L. Nimmo; Chaevien Clendinen; Arthur S. Edison; Clemens Anklin

Journal of Natural Products 2015 Volume 78(Issue 6) pp:1415-1421

Publication Date(Web):June 10, 2015

DOI:10.1021/acs.jnatprod.5b00337

Deuterium is one of the few stable isotopes that have the capacity to significantly alter a compound’s chemical and biological properties. The addition of a single neutron to a protium atom results in the near doubling of its mass, which gives rise to deuterium’s characteristic isotope effects. Since the incorporation of deuterium into organic substrates is known to alter enzyme/protein–substrate interactions, we tested the extent to which deuterium enrichment would modify fungal secondary metabolite production. Several fungal cultures were tested, and in all cases their secondary metabolomes were marked by changes in natural product production. Workup of one Aspergillus sp. grown under deuterium-enrichment conditions resulted in the production of several secondary metabolites not previously detected from the fungus. Bioassay testing revealed that in comparison to the inactive crude fungal extract derived from growing the fungus under non-deuterium-enriched conditions, an extract derived from the same isolate cultured in a deuterium-enriched medium inhibited methicillin-resistant Staphylococcus aureus. Using an assortment of NMR and mass spectrometry experiments, we were able to identify the bacterial inhibitor as an isotope-labeled version of pigmentosin A (6). Five additional isotopically labeled metabolites were also obtained from the fungus including brevianamide F (1), stephacidin A (2), notoamide D (3), notoamide L (4), and notoamide C (5). Given the assorted changes observed in the secondary metabolite profiles of this and other fungi grown in deuterium-enriched environments, as well as the fact that 1 and 3–6 had not been previously observed from the Aspergillus sp. isolate used in this study, we propose that deuterium enrichment might offer an effective method for further expanding a fungus’s chemical diversity potential.

A Potent HDAC Inhibitor, 1-Alaninechlamydocin, from a Tolypocladium sp. Induces G2/M Cell Cycle Arrest and Apoptosis in MIA PaCa-2 Cells

Co-reporter:Lin Du ; April L. Risinger ; Jarrod B. King ; Douglas R. Powell

Journal of Natural Products 2014 Volume 77(Issue 7) pp:1753-1757

Publication Date(Web):July 7, 2014

DOI:10.1021/np500387h

The cyclic tetrapeptide 1-alaninechlamydocin was purified from a Great Lakes-derived fungal isolate identified as a Tolypocladium sp. Although the planar structure was previously described, a detailed analysis of its spectroscopic data and biological activity are reported here for the first time. Its absolute configuration was determined using a combination of spectroscopic (1H–1H ROESY, ECD, and X-ray diffraction) and chemical (Marfey’s analysis) methods. 1-Alaninechlamydocin showed potent antiproliferative/cytotoxic activities in a human pancreatic cancer cell line (MIA PaCa-2) at low-nanomolar concentrations (GI50 5.3 nM, TGI 8.8 nM, LC50 22 nM). Further analysis revealed that 1-alaninechlamydocin induced G2/M cell cycle arrest and apoptosis. Similar to other cyclic epoxytetrapeptides, the inhibitory effects of 1-alaninechlamydocin are proposed to be produced primarily via inhibition of histone deacetylase (HDAC) activity.

Bioactive Sulfur-Containing Sulochrin Dimers and Other Metabolites from an Alternaria sp. Isolate from a Hawaiian Soil Sample

Co-reporter:Shengxin Cai ; Jarrod B. King ; Lin Du ; Douglas R. Powell

Journal of Natural Products 2014 Volume 77(Issue 10) pp:2280-2287

Publication Date(Web):September 29, 2014

DOI:10.1021/np5005449

Polluxochrin (1) and dioschrin (2), two new dimers of sulochrin linked by thioether bonds, were purified from an Alternaria sp. isolate obtained from a Hawaiian soil sample. The structures of the two metabolites were established by NMR, mass spectrometry data, and X-ray analysis. Metabolite 1 was determined to be susceptible to intramolecular cyclization under aqueous conditions, resulting in the generation of 2 as well as another dimeric compound, castochrin (3). An additional nine new metabolites were also obtained, including four new pyrenochaetic acid derivatives (8–11), one new asterric acid analogue (13), and four new secalonic acid analogues (14–17). Bioassay analysis of these compounds revealed 1–3 displayed antimicrobial and weak cytotoxic activities.

Polyketide Glycosides from Bionectria ochroleuca Inhibit Candida albicans Biofilm Formation

Co-reporter:Bin Wang ; Jianlan You ; Jarrod B. King ; Shengxin Cai ; Elizabeth Park ; Douglas R. Powell

Journal of Natural Products 2014 Volume 77(Issue 10) pp:2273-2279

Publication Date(Web):October 10, 2014

DOI:10.1021/np500531j

One of the challenges presented by Candida infections is that many of the isolates encountered in the clinic produce biofilms, which can decrease these pathogens’ susceptibilities to standard-of-care antibiotic therapies. Inhibitors of fungal biofilm formation offer a potential solution to counteracting some of the problems associated with Candida infections. A screening campaign utilizing samples from our fungal extract library revealed that a Bionectria ochroleuca isolate cultured on Cheerios breakfast cereal produced metabolites that blocked the in vitro formation of Candida albicans biofilms. A scale-up culture of the fungus was undertaken using mycobags (also known as mushroom bags or spawn bags), which afforded four known [TMC-151s C–F (1–4)] and three new [bionectriols B–D (5–7)] polyketide glycosides. All seven metabolites exhibited potent biofilm inhibition against C. albicans SC5314, as well as exerted synergistic antifungal activities in combination with amphotericin B. In this report, we describe the structure determination of the new metabolites, as well as compare the secondary metabolome profiles of fungi grown in flasks and mycobags. These studies demonstrate that mycobags offer a useful alternative to flask-based cultures for the preparative production of fungal secondary metabolites.

Cytotoxic Dimeric Epipolythiodiketopiperazines from the Ascomycetous Fungus Preussia typharum

Co-reporter:Lin Du ; Andrew J. Robles ; Jarrod B. King ; Susan L. Mooberry

Journal of Natural Products 2014 Volume 77(Issue 6) pp:1459-1466

Publication Date(Web):June 3, 2014

DOI:10.1021/np5002253

Two new dimeric epipolythiodiketopiperazines, preussiadins A (1) and B (2), together with two known diastereomers, leptosins C (6) and A (7), were obtained from the mycelia of a Preussia typharum isolate. The structures of the new compounds were established by spectroscopic methods, and the absolute configurations of 1 and 2 were assigned by chemical transformations and comparisons of quantum chemical ECD and VCD calculations to experimental data. Compound 1 exhibited potent cytotoxic activity in the NCI-60 cell line panel with an average LC50 value of 251 nM. Further studies demonstrated that 1 circumvents P-glycoprotein-mediated drug resistance, yet had no significant antitumor activity in a xenograft UACC-62 melanoma model.

Crowdsourcing Natural Products Discovery to Access Uncharted Dimensions of Fungal Metabolite Diversity

Co-reporter:Dr. Lin Du;Andrew J. Robles;Jarrod B. King;Dr. Douglas R. Powell;Dr. Andrew N. Miller;Dr. Susan L. Mooberry;Dr. Robert H. Cichewicz

Angewandte Chemie International Edition 2014 Volume 53( Issue 3) pp:804-809

Publication Date(Web):

DOI:10.1002/anie.201306549

Abstract

A fundamental component for success in drug discovery is the ability to assemble and screen compounds that encompass a broad swath of biologically relevant chemical-diversity space. Achieving this goal in a natural-products-based setting requires access to a wide range of biologically diverse specimens. For this reason, we introduced a crowdsourcing program in which citizen scientists furnish soil samples from which new microbial isolates are procured. Illustrating the strength of this approach, we obtained a unique fungal metabolite, maximiscin, from a crowdsourced Alaskan soil sample. Maximiscin, which exhibits a putative combination of polyketide synthase (PKS), non-ribosomal peptide synthetase (NRPS), and shikimate pathway components, was identified as an inhibitor of UACC-62 melanoma cells (LC50=0.93 μM). The metabolite also exhibited efficacy in a xenograft mouse model. These results underscore the value of building cooperative relationships between research teams and citizen scientists to enrich drug discovery efforts.

Spiro Fused Diterpene–Indole Alkaloids from a Creek-Bottom-Derived Aspergillus terreus

Co-reporter:Shengxin Cai, Lin Du, Alexandra L. Gerea, Jarrod B. King, Jianlan You, and Robert H. Cichewicz

Organic Letters 2013 Volume 15(Issue 16) pp:4186-4189

Publication Date(Web):August 7, 2013

DOI:10.1021/ol401891z

Four metabolites, teraspiridoles A–D (2–5), formed from the merger of a diterpene and modified indole scaffold were obtained from an Aspergillus terreus isolate. The structures and absolute configurations of these natural products were established using NMR, mass spectrometry, Marfey’s method, VCD, and ECD data. Teraspiridole B (3) exhibited weak inhibition of planaria regeneration/survival.

Small-Molecule Suppressors of Candida albicans Biofilm Formation Synergistically Enhance the Antifungal Activity of Amphotericin B against Clinical Candida Isolates

Co-reporter:Jianlan You, Lin Du, Jarrod B. King, Brian E. Hall, and Robert H. Cichewicz

ACS Chemical Biology 2013 Volume 8(Issue 4) pp:840

Publication Date(Web):February 6, 2013

DOI:10.1021/cb400009f

A new class of fungal biofilm inhibitors represented by shearinines D (3) and E (4) were obtained from a Penicillium sp. isolate. The inhibitory activities of 3 and 4 were characterized using a new imaging flow-cytometer technique, which enabled the rapid phenotypic analysis of Candida albicans cell types (budding yeast cells, germ tube cells, pseudohyphae, and hyphae) in biofilm populations. The results were confirmed by experimental data obtained from three-dimensional confocal laser scanning microscopy and 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) assays. These data indicate that 3 and 4 inhibited C. albicans biofilm formation by blocking the outgrowth of hyphae at a relatively late stage of biofilm development (IC50 = 8.5 and 7.6 μM, respectively). However, 3 and 4 demonstrated comparatively weak activity at disrupting existing biofilms. Compounds 3 and 4 also exhibited synergistic activities with amphotericin B against C. albicans and other clinical Candida isolates by enhancing the potency of amphotericin B up to 8-fold against cells in both developing and established biofilms. These data suggest that the Candida biofilm disruption and amphotericin B potentiating effects of 3 and 4 could be mediated through multiple biological targets. The shearinines are good tools for testing the potential advantages of using adjunctive therapies in combination with antifungals.

Fungal biofilm inhibitors from a human oral microbiome-derived bacterium

Co-reporter:Xiaoru Wang, Lin Du, Jianlan You, Jarrod B. King and Robert H. Cichewicz

Organic & Biomolecular Chemistry 2012 vol. 10(Issue 10) pp:2044-2050

Publication Date(Web):22 Dec 2011

DOI:10.1039/C2OB06856G

The human mouth is home to a rich assortment of native and transient microorganisms. One of the commonly encountered bacterial species, Streptococcus mutans, was shown to generate the novel hybrid polyketide-nonribosomal peptide metabolite mutanobactin A (1). We have characterized three new analogues, mutanobactins B-D (2–4), and subjected these compounds to further biomedical evaluation. Metabolites 1, 2, and 4 were found to inhibit biofilm formation by the fungal oral-pathogen Candida albicans. Compound 4 was the most potent metabolite with an IC50 value of 5.3 ± 0.9 μM. Using a combination of Marfey's analysis, proton spin–spin coupling, and 1H-1H NOESY data, we proposed absolute configuration assignments in toto for 1–3 and a partial assignment for 4. In addition, feeding studies with isotopically labeled precursor metabolites (acetate and amino acids) have helped to determine the biosynthetic origins of this unique natural product family.

Waikialoid A Suppresses Hyphal Morphogenesis and Inhibits Biofilm Development in Pathogenic Candida albicans

Co-reporter:Xiaoru Wang, Jianlan You, Jarrod B. King, Douglas R. Powell, and Robert H. Cichewicz

Journal of Natural Products 2012 Volume 75(Issue 4) pp:707-715

Publication Date(Web):March 8, 2012

DOI:10.1021/np2009994

A chemically prolific strain of Aspergillus was isolated from a soil sample collected near Waikiki Beach, Honolulu, Hawaii. The fungus produced several secondary metabolites, which were purified and placed in our natural products library and were later screened for substances capable of inhibiting biofilm formation by Candida albicans. It was determined that one of the secondary metabolites from the Hawaiian fungal isolate, a new complex prenylated indole alkaloid named waikialoid A (1), inhibited biofilm formation with an IC50 value of 1.4 μM. Another structurally unrelated, presumably polyketide metabolite, waikialide A (15), also inhibited C. albicans biofilm formation, but was much less potent (IC50 value of 32.4 μM). Microscopy studies revealed that compound 1 also inhibited C. albicans hyphal morphogenesis. While metabolite 1 appears ineffective at disrupting preformed biofilms, the accumulated data indicate that the new compound may exert its activity against C. albicans during the early stages of surface colonization involving cell adherence, hyphal development, and/or biofilm assembly. Unlike some other stephacidin/notoamide compounds, metabolite 1 was not cytotoxic to fungi or human cells (up to 200 μM), which makes this an intriguing model compound for studying the adjunctive use of biofilm inhibitors in combination with standard antifungal antibiotics.

Diarylcyclopentendione Metabolite Obtained from a Preussia typharum Isolate Procured Using an Unconventional Cultivation Approach

Co-reporter:Lin Du ; Jarrod B. King ; Brian H. Morrow ; Jana K. Shen ; Andrew N. Miller

Journal of Natural Products 2012 Volume 75(Issue 10) pp:1819-1823

Publication Date(Web):October 9, 2012

DOI:10.1021/np300473h

An uncommon 2,5-diarylcyclopentenone compound, preussidone (1), and a new biphenyl compound, 1′,5-dimethoxy-3,5′-dimethyl-2,3′-oxybiphenyl-1,2′-diol (4), together with two known biphenyl compounds, 5-methoxy-3,5′-dimethyl-2,3′-oxybiphenyl-1,1′,2′-triol (2) and cyperin (3), were obtained from a Preussia typharum isolate that was procured using a panel of unconventional media formulations. The structures of the new compounds were established by NMR and mass spectrometry, while the absolute configuration of 1 was assigned by quantum chemical ECD and VCD calculations. The antimicrobial and DPPH radical scavenging activities of 1–4 were tested. Compounds 2 and 4 exhibited DPPH radical scavenging activities that were comparable to the positive control ascorbic acid.

Production of Cytotoxic Glidobactins/Luminmycins by Photorhabdus asymbiotica in Liquid Media and Live Crickets

Co-reporter:Christine M. Theodore, Jarrod B. King, Jianlan You, and Robert H. Cichewicz

Journal of Natural Products 2012 Volume 75(Issue 11) pp:2007-2011

Publication Date(Web):October 24, 2012

DOI:10.1021/np300623x

Photorhabdus asymbiotica engages in a two-part life cycle that requires adaptation to both symbiotic and pathogenic phases. The genome of P. asymbiotica contains several gene clusters, which are predicted to be involved in the biosynthesis of unique secondary metabolites that are hypothesized to enhance the bacterium’s pathogenic capabilities. However, recent reports on Photorhabdus secondary metabolite production have indicated that many of its genes are silent under laboratory culture conditions. Using a circumscribed panel of media and alternative fermentation conditions, we have successfully achieved the production of a series of new and known glidobactin/luminmycin derivatives from P. asymbiotica including glidobactin A (1), luminmycin A (2), and luminmycin D (3). These compounds were also obtained upon infection of live crickets with the bacterium. Luminmycin D showed cytotoxicity against human pancreatic cells (IC50 of 0.11 μM), as well as proteasome inhibition (IC50 of 0.38 μM).

Secondary metabolites produced by fungi derived from a microbial mat encountered in an iron-rich natural spring

Co-reporter:Alexandra L. Gerea, Katie M. Branscum, Jarrod B. King, Jianlan You, Douglas R. Powell, Andrew N. Miller, John R. Spear, Robert H. Cichewicz

Tetrahedron Letters 2012 Volume 53(Issue 32) pp:4202-4205

Publication Date(Web):8 August 2012

DOI:10.1016/j.tetlet.2012.05.156

A collection of fungal isolates was obtained from a complex microbial mat, which occupied an iron-rich freshwater spring that feeds into Clear Creek, Golden, Colorado, USA. Two of the fungal isolates, a Glomeromycete (possibly Entrophospora sp.) and a Dothideomycete (possibly Phaeosphaeria sp.), were investigated for bioactive secondary metabolites. In total, six new compounds consisting of clearanols A–E (5, 6, 10–12) and disulochrin (7) were purified and their structures were determined. Disulochrin exhibited modest antibacterial activity against methicillin-resistant Staphylococcus aureus, whereas clearanol C showed weak inhibitory activity against Candida albicans biofilm formation.

Bringing natural products into the fold – exploring the therapeutic lead potential of secondary metabolites for the treatment of protein-misfolding-related neurodegenerative diseases

Co-reporter:P. Matthew Joyner and Robert H. Cichewicz

Natural Product Reports 2011 vol. 28(Issue 1) pp:26-47

Publication Date(Web):07 Oct 2010

DOI:10.1039/C0NP00017E

Covering: up to June 2010

Briarane Diterpenes Diminish COX-2 Expression in Human Colon Adenocarcinoma Cells

Co-reporter:P. Matthew Joyner, Amanda L. Waters, Russell B. Williams, Douglas R. Powell, Naveena B. Janakiram, Chinthalapally V. Rao, and Robert H. Cichewicz

Journal of Natural Products 2011 Volume 74(Issue 4) pp:857-861

Publication Date(Web):March 25, 2011

DOI:10.1021/np100775a

Exploration of a soft coral (Briareum sp.) from Vanuatu led to the isolation of three new briaranes, designated brialalepolides A (1), B (2), and C (3). Compounds 2 and 3 reduced the expression of COX-2 in human colon adenocarcinoma cells, as well as in murine macrophage cells. This is significant because the metabolic products of COX-2 have been implicated in the pathogenesis of colon cancer and other diseases.

Reappraising the Structures and Distribution of Metabolites from Black Aspergilli Containing Uncommon 2-Benzyl-4H-pyran-4-one and 2-Benzylpyridin-4(1H)-one Systems

Co-reporter:Jon C. Henrikson, Trevor K. Ellis, Jarrod B. King, and Robert H. Cichewicz

Journal of Natural Products 2011 Volume 74(Issue 9) pp:1959-1964

Publication Date(Web):August 19, 2011

DOI:10.1021/np200454z

To date, natural products containing 2-benzyl-4H-pyran-4-one and 2-benzylpyridin-4(1H)-one substructures have been encountered in relatively few fungi outside of the black aspergilli clade. While exploring the occurrence of these compounds among Aspergillus spp., it was determined that the structures of the unusual furopyrrols tensidols A and B (5 and 6) and JBIR-86 and JBIR-87 (9 and 10) were incorrect and should be reassigned as 2-benzyl-4H-pyran-4-ones (7, 8, 11e, and 12, respectively). The origin of the unique N-phenyl groups in the 2-benzylpyridin-4(1H)-ones nygerones A and B (1 and 2) were also examined, and it was established that N-phenylamides added to the culture medium were suitable substrates for generating these metabolites; however, this phenomenon remained limited to a single fungus in our collection (Aspergillus niger ATCC 1015). A variety of 2-benzyl-4H-pyran-4-ones and 2-benzylpyridin-4(1H)-ones were detected among the black aspergilli, but only pestalamide B (13) was found in all 11 of the tested strains. These metabolites, as well as a group of synthetic analogues, demonstrated weak antifungal activity against several Candida strains, Aspergillus flavus, and Aspergillus fumigatus.

Epigenome manipulation as a pathway to new natural product scaffolds and their congeners

Co-reporter:Robert H. Cichewicz

Natural Product Reports 2010 vol. 27(Issue 1) pp:11-22

Publication Date(Web):27 Oct 2009

DOI:10.1039/B920860G

Covering: up to the end of September 2009

Chemical Epigenetics Alters the Secondary Metabolite Composition of Guttate Excreted by an Atlantic-Forest-Soil-Derived Penicillium citreonigrum

Co-reporter:Xiaoru Wang, José G. Sena Filho, Ashley R. Hoover, Jarrod B. King, Trevor K. Ellis, Douglas R. Powell and Robert H. Cichewicz

Journal of Natural Products 2010 Volume 73(Issue 5) pp:942-948

Publication Date(Web):May 7, 2010

DOI:10.1021/np100142h

Chemical epigenetic manipulation of Penicillium citreonigrum led to profound changes in the secondary metabolite profile of its guttate. While guttate from control cultures exhibited a relatively simple assemblage of secondary metabolites, the guttate collected from cultures treated with 50 μM 5-azacytidine (a DNA methyltransferase inhibitor) was highly enriched in compounds representing at least three distinct biosynthetic families. The metabolites obtained from the fungus included six azaphilones (sclerotiorin (1), sclerotioramine (6), ochrephilone (2), dechloroisochromophilone III (3), dechloroisochromophilone IV (4), and 6-((3E,5E)-5,7-dimethyl-2-methylenenona-3,5-dienyl)-2,4-dihydroxy-3-methylbenzaldehyde (5)), pencolide (7), and two new meroterpenes (atlantinones A and B (9 and 10, respectively)). While pencolide was detected in the exudates of both control and 5-azacytidine-treated cultures, all of the other natural products were found exclusively in the guttates of the epigenetically modified fungus. All of the metabolites from the P. citreonigrum guttate were tested for antimicrobial activity in a disk diffusion assay. Both sclerotiorin and sclerotioramine caused modest inhibition of Staphylococcus epidermidis growth; however, only sclerotioramine was active against a panel of Candida strains.

Probing the Metabolic Aberrations Underlying Mutant Huntingtin Toxicity in Yeast and Assessing Their Degree of Preservation in Humans and Mice

Co-reporter:P. Matthew Joyner, Ronni M. Matheke, Lindsey M. Smith and Robert H. Cichewicz

Journal of Proteome Research 2010 Volume 9(Issue 1) pp:404-412

Publication Date(Web):2017-2-22

DOI:10.1021/pr900734g

Metabolomics is a powerful multiparameter tool for evaluating phenotypic traits associated with disease processes. We have used 1H NMR metabolome profiling to characterize metabolic aberrations in a yeast model of Huntington’s disease that are attributable to the mutant huntingtin protein’s gain-of-toxic-function effects. A group of 11 metabolites (alanine, acetate, galactose, glutamine, glycerol, histidine, proline, succinate, threonine, trehalose, and valine) exhibited significant concentration changes in yeast expressing the N-terminal fragment of a mutant human huntingtin gene. Correspondence analysis was used to compare results from our yeast model to data reported from transgenic mice expressing a mutant huntingtin gene fragment and Huntington’s disease patients. This technique enabled us to identify a variety of both model-specific (pertaining to a single species) and conserved (observed in multiple species) biomarkers related to mutant huntingtin’s toxicity. Among the 59 metabolites identified, four compounds (alanine, glutamine, glycerol, and valine) changed significantly in concentration in all three Huntington’s disease systems. We propose that alanine, glutamine, glycerol, and valine should be considered as promising biomarkers for evaluating new Huntington’s disease therapies, as well as for providing unique insight into the mechanisms associated with mutant huntingtin toxicity.

Mutanobactin A from the human oral pathogen Streptococcus mutans is a cross-kingdom regulator of the yeast-mycelium transition

Co-reporter:P. Matthew Joyner, Jinman Liu, Zhijun Zhang, Justin Merritt, Fengxia Qi and Robert H. Cichewicz

Organic & Biomolecular Chemistry 2010 vol. 8(Issue 24) pp:5486-5489

Publication Date(Web):20 Sep 2010

DOI:10.1039/C0OB00579G

The recent investigation of a gene cluster encoding for a hybrid PKS-NRPS metabolite in the oral pathogen Streptococcus mutans UA159 yielded evidence that this natural product might play an important role regulating a range of stress tolerance factors. We have now characterized the major compound generated from this gene cluster, mutanobactin A, and demonstrated that this secondary metabolite is also capable of influencing the yeast-mycelium transition of Candida albicans.

A chemical epigenetics approach for engineering the in situbiosynthesis of a cryptic natural product from Aspergillus niger

Co-reporter:Jon C. Henrikson, Ashley R. Hoover, P. Matthew Joyner and Robert H. Cichewicz

Organic & Biomolecular Chemistry 2009 vol. 7(Issue 3) pp:435-438

Publication Date(Web):2008/12/11

DOI:10.1039/B819208A

A new fungal metabolite, nygerone A (1), featuring a unique 1-phenylpyridin-4(1H)-one core that had previously not been reported from any natural source, has been obtained from Aspergillus niger using a chemical epigenetics methodology.

Phenylethanoid and Lignan Glycosides from Polar Extracts of Lantana, a Genus of Verbenaceous Plants Widely Used in Traditional Herbal Therapies

Co-reporter:José G. Sena Filho, Susan L. Nimmo, Haroudo S. Xavier, José M. Barbosa-Filho and Robert H. Cichewicz

Journal of Natural Products 2009 Volume 72(Issue 7) pp:1344-1347

Publication Date(Web):June 1, 2009

DOI:10.1021/np900086y

Many references to the use of Lantana spp. can be found in the ethnopharmacological literature from locations around the globe. This study was focused on examining constituents from the polar extracts of Lantana radula Sw. and Lantana canescens Kunth, for which no prior chemical investigations had been reported. A new phenylethanoid glycoside, raduloside, and lignan glycoside, radulignan, were identified along with the known compounds alyssonoside, arenarioside, calceolarioside E, isonuomioside, samioside, and verbascoside.

Chemical induction of silent biosynthetic pathway transcription in Aspergillus niger

Co-reporter:K. M. Fisch;A. F. Gillaspy;M. Gipson

Journal of Industrial Microbiology & Biotechnology 2009 Volume 36( Issue 9) pp:1199-1213

Publication Date(Web):2009 September

DOI:10.1007/s10295-009-0601-4

Manipulation of the fungal epigenome is hypothesized to be an effective method for accessing natural products from silent biosynthetic pathways. A library of epigenetic modifiers was tested using the fungus Aspergillus niger to determine the impact of small-molecule inhibitors on reversing the transcriptional suppression of biosynthetic genes involved in polyketide (PKS), non-ribosomal peptide (NRPS), and hybrid PKS-NRPS (HPN) production. Examination of expressed sequence tag libraries from A. niger demonstrated that >70% of its PKS-, NRPS-, and HPN-encoding gene clusters were transcriptionally suppressed under standard laboratory culture conditions. Using a chemical epigenetic methodology, we showed that treatment of A. niger with suberoylanilide hydroxamic acid and 5-azacytidine led to the transcriptional upregulation of many secondary-metabolite-encoding biosynthetic gene clusters. Chemical epigenetic modifiers exhibited positional biases for upregulating chromosomally distal gene clusters. In addition, a phylogenetic-based preference was noted in the upregulation of reducing clade I PKS gene clusters, while reducing clade IV PKS gene clusters were largely unaffected. Manipulating epigenetic features in fungi is a powerful method for accessing the products of silent biosynthetic pathways. Moreover, this approach can be readily incorporated into modern microbial screening operations.

Epigenetic remodeling of the fungal secondary metabolome

Co-reporter:Russell B. Williams, Jon C. Henrikson, Ashley R. Hoover, Andrlynn E. Lee and Robert H. Cichewicz

Organic & Biomolecular Chemistry 2008 vol. 6(Issue 11) pp:1895-1897

Publication Date(Web):14 Apr 2008

DOI:10.1039/B804701D

Fungi treated with DNA methyltransferase and histone deacetylase inhibitors exhibited natural product profiles with enhanced chemical diversity demonstrating that small-molecule epigenetic modifiers are effective tools for rationally controlling the native expression of fungal biosynthetic pathways and generating new biomolecules.

Bioactivity Profiling with Parallel Mass Spectrometry Reveals an Assemblage of Green Tea Metabolites Affording Protection against Human Huntingtin and α-Synuclein Toxicity

Co-reporter:Russell B. Williams, Will R. Gutekunst, P. Matthew Joyner, Wenzhen Duan, Qing Li, Christopher A. Ross, Todd D. Williams and Robert H. Cichewicz

Journal of Agricultural and Food Chemistry 2007 Volume 55(Issue 23) pp:9450-9456

Publication Date(Web):October 19, 2007

DOI:10.1021/jf072241x

Aberrant protein aggregation and misfolding are key pathological features of many neurodegenerative disorders, including Huntington’s and Parkinson’s diseases. Compounds that offer protection from toxicity associated with aggregation-prone neurodegenerative proteins may have applications for the treatment of a multitude of disorders. A high-throughput bioassay system with parallel electrospray ionization mass spectrometry screening has been designed for critical evaluation of milligram quantities of natural product extracts, including dietary substances, for compounds of pharmacological relevance to the treatment of human neurodegenerative diseases. Using Saccharomyces cerevisiae strains engineered to express mutant human huntingtin and α-synuclein, we are able to identify extracts and compounds that protect cells from toxicity associated with these proteins. Applying this screening paradigm, we determined that a bioactive green tea extract contains an assemblage of catechins that were individually characterized for their respective protective effects against huntingtin and α-synuclein toxicity.

Reassessing the ichthyotoxin profile of cultured Prymnesium parvum (golden algae) and comparing it to samples collected from recent freshwater bloom and fish kill events in North America

Co-reporter:Jon C. Henrikson, Majed S. Gharfeh, Anne C. Easton, James D. Easton, Karen L. Glenn, Miriam Shadfan, Susan L. Mooberry, K. David Hambright, Robert H. Cichewicz

Toxicon (15 June 2010) Volume 55(Issue 7) pp:1396-1404

Publication Date(Web):15 June 2010

DOI:10.1016/j.toxicon.2010.02.017

Within the last two decades, Prymnesium parvum (golden algae) has rapidly spread into inland waterways across the southern portion of North America and this organism has now appeared in more northerly distributed watersheds. In its wake, golden algae blooms have left an alarming trail of ecological devastation, namely massive fish kills, which are threatening the economic and recreational value of freshwater systems throughout the United States. To further understand the nature of this emerging crisis, our group investigated the chemical nature of the toxin(s) produced by P. parvum. We approached the problem using a two-pronged strategy that included analyzing both laboratory-grown golden algae and field-collected samples of P. parvum. Our results demonstrate that there is a striking difference in the toxin profiles for these two systems. An assemblage of potently ichthyotoxic fatty acids consisting primarily of stearidonic acid was identified in P. parvum cultures. While the concentration of the fatty acids alone was sufficient to account for the rapid-onset ichthyotoxic properties of cultured P. parvum, we also detected a second type of highly labile ichthyotoxic substance(s) in laboratory-grown golden algae that remains uncharacterized. In contrast, the amounts of stearidonic acid and its related congeners present in samples from recent bloom and fish kill sites fell well below the limits necessary to induce acute toxicity in fish. However, a highly labile ichthyotoxic substance, which is similar to the one found in laboratory-grown P. parvum cultures, was also detected. We propose that the uncharacterized labile metabolite produced by P. parvum is responsible for golden algae's devastating fish killing effects. Moreover, we have determined that the biologically-relevant ichthyotoxins produced by P. parvum are not the prymnesins as is widely believed. Our results suggest that further intensive efforts will be required to chemically define P. parvum's ichthyotoxins under natural bloom conditions.

Chlorinated Polyketide Obtained from a Daldinia sp. Treated with the Epigenetic Modifier Suberoylanilide Hydroxamic Acid

Co-reporter:Lin Du ; Jarrod B. King

Journal of Natural Products () pp:

Publication Date(Web):October 22, 2014

DOI:10.1021/np500522z

Mutanobactin A from the human oral pathogen Streptococcus mutans is a cross-kingdom regulator of the yeast-mycelium transition

Co-reporter:P. Matthew Joyner, Jinman Liu, Zhijun Zhang, Justin Merritt, Fengxia Qi and Robert H. Cichewicz

Organic & Biomolecular Chemistry 2010 - vol. 8(Issue 24) pp:NaN5489-5489

Publication Date(Web):2010/09/20

DOI:10.1039/C0OB00579G

A chemical epigenetics approach for engineering the in situbiosynthesis of a cryptic natural product from Aspergillus niger

Co-reporter:Jon C. Henrikson, Ashley R. Hoover, P. Matthew Joyner and Robert H. Cichewicz