Beyond traditional screening: Unveiling antibiotic potentials of actinomycetes in extreme environments.

Extreme ecosystems are a rich source of specialized metabolites that can overcome multidrug resistance. However, the low efficiency of traditional exploratory research in discovering new antibiotics remains a major limitation. We hypothesized that actinomycetes may have the ability to produce antibiotics in the extremes of a changing natural environment.

Acroamine A, a 2-Amino Adenine Alkaloid from the Marine Soft Coral and Its Semisynthetic Derivatives That Inhibit cAMP-Dependent Protein Kinase A Catalytic Subunit Alpha.

A high throughput screen performed to identify catalytic inhibitors of the oncogenic fusion form of cAMP-dependent protein kinase A catalytic subunit alpha (J-PKAcα) found an individual fraction from an organic extract of the marine soft coral as active. Bioassay-guided isolation led to the identification of a 2-amino adenine alkaloid acroamine A (), the first secondary metabolite discovered from this genus and previously reported as a synthetic product. As a naturally occurring protein kinase inhibitor, to unambiguously assign its chemical structure using modern spectroscopic and spectrometric techniques, five -methylated derivatives acroamines A-A (-) were semisynthesized.

Chemoreactive 2,5-Diketopiperazines from a sp., Structure Revision of Reported Analogues and Proposed Facile Transformation Pathways.

Merkel cell carcinoma (MCC) is a rare and aggressive cutaneous cancer. Two new prenylated indole 2,5-diketopiperazine alkaloids, brevianamides E1 () and E2 (), were isolated from a fungus. Both compounds showed moderate cytotoxic activity against select MCC cell lines (i.

Neopetrotaurines A-C, Isoquinoline Alkaloids with an Unprecedented Taurine Bridge from the Sponge sp.

Neopetrotaurines A-C (-), unusual alkaloids possessing two isoquinoline-derived moieties that are linked via a unique taurine bridge, were isolated from a sp. marine sponge. These new compounds have proton-deficient structural scaffolds that are difficult to unambiguously assign using only conventional 2- and 3-bond H-C and H-N heteronuclear correlation data.

Cytotoxicity and Antitumor Activity of Arglabin and its Derivatives.

Background: At present, more than 8000 sesquiterpene lactones have been isolated and described from natural sources, a significant part of which has cytotoxicity and antitumor activity. One of the practically available sesquiterpene lactones is arglabin, which, as a renewable material, is used for the synthesis of new compounds. The article presents data on the study of cytotoxicity and antitumor activity of the arglabin and its derivatives using molecular modeling methods and, in the experiment and .

Novel Cytotoxic Sesquiterpene Coumarin Ethers and Sulfur-Containing Compounds from the Roots of .

Six new sesquiterpene coumarin ethers, namely turcicanol A (), turcicanol A acetate (), turcicanol B (), turcica ketone (), 11'-dehydrokaratavicinol (), and galbanaldehyde (), and one new sulfur-containing compound, namely turcicasulphide (), along with thirty-two known secondary metabolites were isolated from the root of the endemic species Akalın, Miski, & Tuncay through a bioassay-guided isolation approach. The structures of the new compounds were elucidated by spectroscopic analysis and comparison with the literature. Cell growth inhibition of colon cancer cell lines (COLO205 and HCT116) and kidney cancer cell lines (UO31 and A498) was used to guide isolation.

Biochemical Discovery, Intracellular Evaluation, and Crystallographic Characterization of Synthetic and Natural Product Adenosine 3',5'-Cyclic Monophosphate-Dependent Protein Kinase A (PKA) Inhibitors.

The recent demonstration that adenosine 3',5'-cyclic monophosphate (cAMP)-dependent protein kinase A (PKA) plays an oncogenic role in a number of important cancers has led to a renaissance in drug development interest targeting this kinase. We therefore have established a suite of biochemical, cell-based, and structural biology assays for identifying and evaluating new pharmacophores for PKA inhibition. This discovery process started with a 384-well high-throughput screen of more than 200,000 substances, including fractionated natural product extracts.

Biological Effects of Modifications of the Englerin A Glycolate.

Modifications at the glycolate moiety of englerin A were made to explore variations at the most sensitive site on the molecule for activity in the NCI 60 screen, wherein englerin A is highly potent and selective for renal cancer cells. Replacement of the glycolate by other functionalities as well as esterification of the glycolate hydroxyl yielded compounds which displayed excellent selectivity and potency compared with the natural product. TRPC4/5 ion channel experiments with five compounds showed delayed or reduced agonism with TRPC5, at much higher concentrations than englerin A.

Substitution of a triazole for the central olefin in biologically active stilbenes.

The stilbene moiety is commonly found in natural products and these compounds display an extraordinary range of biological activity. Efforts to derive useful drugs from stilbenes must address the potential liabilities of this structure, including a propensity for cis/trans isomerization. To identify olefin replacements that address this limitation while preserving biological activity we have prepared analogues of two bioactive stilbenes, a pawhuskin and a schweinfurthin, where a 1,2,3-triazole ring formally replaces the stilbene double bond.

Tolypocladamides A-G: Cytotoxic Peptaibols from .

Seven new peptaibols named tolypocladamides A-G have been isolated from an extract of the fungus , which inhibits the interaction between Raf and oncogenic Ras in a cell-based high-throughput screening assay. Each peptaibol contains 11 amino acid residues, an octanoyl or decanoyl fatty acid chain at the N-terminus, and a leucinol moiety at the C-terminus. The peptaibol sequences were elucidated on the basis of 2D NMR and mass spectral fragmentation analyses.

Synthesis of a Coumarin-Based Analogue of Schweinfurthin F.

The natural schweinfurthins are stilbenes with significant antiproliferative activity and an uncertain mechanism of action. To obtain a fluorescent analogue with minimal deviation from the natural structure, a coumarin ring system was annulated to the D-ring, creating a new analogue of schweinfurthin F. This stilbene was prepared through a convergent synthesis, with a Horner-Wadsworth-Emmons condensation employed to form the central stilbene olefin.

Neopetrothiazide: An Intriguing Pentacyclic Thiazide Alkaloid from the Sponge sp.

Neopetrothiazide (), a pentacyclic isoquinoline quinone, was isolated from a sp. sponge. The structure elucidation was facilitated by utilizing long-range heteronuclear single quantum multiple bond correlation (LR-HSQMBC) and heteronuclear multiple bond correlation (HMBC) nuclear magnetic resonance (NMR) pulse sequences optimized to detect four- and five-bond H-C heteronuclear correlations.

A Molecular Networking Strategy: High-Throughput Screening and Chemical Analysis of Brazilian Cerrado Plant Extracts against Cancer Cells.

Plants have historically been a rich source of successful anticancer drugs and chemotherapeutic agents, with research indicating that this trend will continue. In this contribution, we performed high-throughput cytotoxicity screening of 702 extracts from 95 plant species, representing 40 families of the Brazilian Cerrado biome. Activity was investigated against the following cancer cell lines: colon (Colo205 and Km12), renal (A498 and U031), liver (HEP3B and SKHEP), and osteosarcoma (MG63 and MG63.

Scaffold hopping and optimisation of 3',4'-dihydroxyphenyl- containing thienopyrimidinones: synthesis of quinazolinone derivatives as novel allosteric inhibitors of HIV-1 reverse transcriptase-associated ribonuclease H.

Bioisosteric replacement and scaffold hopping are powerful strategies in drug design useful for rationally modifying a hit compound towards novel lead therapeutic agents. Recently, we reported a series of thienopyrimidinones that compromise dynamics at the p66/p51 HIV-1 reverse transcriptase (RT)-associated Ribonuclease H (RNase H) dimer interface, thereby allosterically interrupting catalysis by altering the active site geometry. Although they exhibited good submicromolar activity, the isosteric replacement of the thiophene ring, a potential toxicophore, is warranted.

Bridgehead Modifications of Englerin A Reduce TRPC4 Activity and Intravenous Toxicity but not Cell Growth Inhibition.

Modifications at the bridgehead position of englerin A were made to explore the effects of variation at this site on the molecule for biological activity, as judged by the NCI 60 screen, in which englerin A is highly potent and selective for renal cancer cells. Replacement of the isopropyl group by other, larger substituents yielded compounds which displayed excellent selectivity and potency comparable to the natural product. Selected compounds were also evaluated for their effect on the ion channel TRPC4 as well as for intravenous toxicity in mice, and these had lower potency in both assays compared to englerin A.

Identification of potential modulators of osteosarcoma metastasis by high-throughput cellular screening of natural products.

A high-throughput screening assay was developed and applied to a large library of natural product extract samples, in order to identify compounds which preferentially inhibited the in vitro 2D growth of a highly metastatic osteosarcoma cell line (MG63.3) compared to a cognate parental cell line (MG63) with low metastatic potential. Evaluation of differentially active natural product extracts with bioassay-guided fractionation led to the identification of lovastatin (IC  = 11 µm) and the limonoid toosendanin (IC  = 26 nm).

Neopapillarine, an Unusual Coumarino-Alkaloid from the Root Extract of with Cytotoxic Activity on Renal Cancer Cells.

Several simple and prenylated coumarin derivatives were isolated from the dichloromethane extract of the root of based on moderate cytotoxic activity of the extract in COLO205, KM12 and MCF7 cancer cells. While the major prenylated furanocoumarin derivatives and osthol isolated from the dichloromethane extract were responsible for the activity in the colon and breast cancer cell lines, the 4'-acylated osthol derivatives including a novel coumarino-alkaloid; neopapillarine) demonstrated selective cytotoxic activity in A498 and UO31 renal cancer cell lines.

Natural Products as a Foundation for Drug Discovery.

Many natural products have been used as drugs for the treatment of diverse indications. Although most U.S.

Madecassic Acid Derivatives as Potential Anticancer Agents: Synthesis and Cytotoxic Evaluation.

A series of novel madecassic acid () derivatives was synthesized, and their cytotoxicity was evaluated against the NCI-60 panel of cancer cell lines. Several analogues exhibited broad-spectrum cytotoxic activities over all nine tumor types represented in the panel, with more potent antiproliferative activities observed against selected cancer cell lines, including multidrug-resistant phenotypes. Among them, compound showed GI (50% growth inhibition) values ranging from 0.

Triple-negative breast cancer cell line sensitivity to englerin A identifies a new, targetable subtype.

Purpose: Triple-negative breast cancers (TNBCs) represent a heterogeneous group of tumors. The lack of targeted therapies combined with the inherently aggressive nature of TNBCs results in a higher relapse rate and poorer overall survival. We evaluated the heterogeneity of TNBC cell lines for TRPC channel expression and sensitivity to cation-disrupting drugs.

Anatolicin, a Highly Potent and Selective Cytotoxic Sesquiterpene Coumarin from the Root Extract of .

Seven known sesquiterpene coumarins and a new sesquiterpene coumarin, anatolicin (), were isolated from the dichloromethane extract of the roots of . Structures of these compounds were elucidated based on their spectral properties. While some of these sesquiterpene coumarins showed modest cytotoxic activity against COLO205, KM12, A498, UO31, and TC32 cancer cell lines, selective cytotoxicity of anatolicin () and 14'-acetoxybadrakemin () were observed at nanomolar level against the UO31 kidney cancer cell line.

Sensitivity of the C-Terminal Nuclease Domain of Kaposi's Sarcoma-Associated Herpesvirus ORF29 to Two Classes of Active-Site Ligands.

Kaposi's sarcoma-associated herpesvirus (KSHV), the etiological agent of Kaposi's sarcoma, belongs to the family, whose members employ a multicomponent terminase to resolve nonparametric viral DNA into genome-length units prior to their packaging. Homology modeling of the ORF29 C-terminal nuclease domain (pORF29C) and bacteriophage Sf6 gp2 have suggested an active site clustered with four acidic residues, D, E, D, and D, that collectively sequester the catalytic divalent metal (Mn) and also provided important insight into a potential inhibitor binding mode. Using this model, we have expressed, purified, and characterized the wild-type pORF29C and variants with substitutions at the proposed active-site residues.

Cytotoxic Triterpenes from and Metabolite Profiling of Celastraceae Species.

The new pentacyclic triterpene 11-hydroxypristimerin (), along with the known metabolites pristimerin (), 6-oxopristimerol () and vitideasin (), were isolated from a root wood extract, following a bioassay-guided fractionation approach. Both the extract and the purified triterpenes displayed pronounced cytotoxic activity against human cancer cell lines. The NCI-60 cell line screen revealed that compound was the most active, with a mean GI of 0.

Tonantzitlolone is a nanomolar potency activator of transient receptor potential canonical 1/4/5 channels.

Background And Purpose: The diterpene ester tonantzitlolone (TZL) is a natural product, which displays cytotoxicity towards certain types of cancer cell such as renal cell carcinoma cells. The effect is similar to that of (-)-englerin A, and so, although it is chemically distinct, we investigated whether TZL also targets transient receptor potential canonical (TRPC) channels of the 1, 4 and 5 type (TRPC1/4/5 channels).

Experimental Approach: The effects of TZL on renal cell carcinoma A498 cells natively expressing TRPC1 and TRPC4, modified HEK293 cells overexpressing TRPC4, TRPC5, TRPC4-TRPC1 or TRPC5-TRPC1 concatemer, TRPC3 or TRPM2, or CHO cells overexpressing TRPV4 were studied by determining changes in intracellular Ca , or whole-cell or excised membrane patch-clamp electrophysiology.

US National Cancer Institute-China Collaborative Studies on Chinese Medicine and Cancer.

Since 2007, the US National Cancer Institute (NCI) Office of Cancer Complementary and Alternative Medicine (OCCAM), together with the Cancer Institute of the China Academy of Chinese Medical Sciences (CICACMS), institutes at China Academy of Sciences and Chinese Academy of Medical Sciences, have engaged in collaborations on Chinese medicine (CM) and cancer research. Through these collaborations, CM drugs and compounds have been studied at NCI labs. This paper summarizes the discoveries and progress on these research projects, exploring the aspects of cancer prevention, botanical drug mechanisms of action and component analysis/quality control (QC), and anticancer activity screening.