Todd L. Capson

Significant Natural Product Biosynthetic Potential of Actinorhizal Symbionts of the Genus Frankia, as Revealed by Comparative Genomic and Proteomic Analyses

ABSTRACT Bacteria of the genus Frankia are mycelium-forming actinomycetes that are found as nitrogen-fixing facultative symbionts of actinorhizal plants. Although soil-dwelling actinomycetes are well-known producers of bioactive compounds, the genus Frankia has largely gone uninvestigated for this potential. Bioinformatic analysis of the genome sequences of Frankia strains ACN14a, CcI3, and EAN1pec revealed an unexpected number of secondary metabolic biosynthesis gene clusters. Our analysis led to the identification of at least 65 biosynthetic gene clusters, the vast majority of which appear to be unique and for which products have not been observed or characterized. More than 25 secondary metabolite structures or structure fragments were predicted, and these are expected to include cyclic peptides, siderophores, pigments, signaling molecules, and specialized lipids. Outside the hopanoid gene locus, no cluster could be convincingly demonstrated to be responsible for the few secondary metabolites previously isolated from other Frankia strains. Few clusters were shared among the three species, demonstrating species-specific biosynthetic diversity. Proteomic analysis of Frankia sp. strains CcI3 and EAN1pec showed that significant and diverse secondary metabolic activity was expressed in laboratory cultures. In addition, several prominent signals in the mass range of peptide natural products were observed in Frankia sp. CcI3 by intact-cell matrix-assisted laser desorption-ionization mass spectrometry (MALDI-MS). This work supports the value of bioinformatic investigation in natural products biosynthesis using genomic information and presents a clear roadmap for natural products discovery in the Frankia genus.

Using ecological criteria to design plant collection strategies for drug discovery

Tropical forests are one of the most diverse and endangered habitats on earth. They have also been portrayed as a source of future pharmaceuticals, yet finding useful compounds can be both scientifically and politically challenging. Increasingly, over the past decade, the potential value of medicinal compounds derived from plants, microorganisms, and animals has been proposed as a tangible benefit of biodiversity, and therefore a basis for promoting its preservation. Ecological theories of plant defense can increase the probability of discovering compounds with activity in bioassays against human disease targets. In addition, conducting research in tropical countries with local scientists provides immediate and lasting benefits for the sustainable use of biodiversity. This new approach to drug discovery has been effective in identifying bioactive leads. It is both an important step towards understanding the medicinal value of biodiversity, and a practical way to link drug discovery with conservation.

Differences in the topoisomerase I cleavage complexes formed by camptothecin and wakayin, a DNA-intercalating marine natural product

Wakayin is a bispyrroloiminoquinone isolated from a Clavelina sp. ascidian by cytotoxicity directed fractionation. Like camptothecin, it has been found to inhibit the topo-isomerase I catalyzed relaxation of supercoiled DNA. Wakayin enhanced cleavage complex formation at the same DNA sequences as camptothecin. Both compounds showed dose-related increases in cleavage complex formation, though wakayins effect is attenuated at high concentrations. Wakayin is a strong DNA binder. Wakayin also differed from camptothecin in that its cleavage complexes were much less stable than those of camptothecin in 0.5 M NaCI. Again in contrast to camptothecin, wakayin stabilized cleavage complexes poorly, if at all, at 0°C.

Malyngolide Dimer, a Bioactive Symmetric Cyclodepside from the Panamanian Marine Cyanobacterium Lyngbya majuscula

Fractionation of the extract of the marine cyanobacterium Lyngbya majuscula collected from Panama led to the isolation of malyngolide dimer (1). The planar structure of 1 was determined using 1D and 2D NMR spectroscopy and HRESI-TOFMS. The absolute configuration was established by chemical degradation followed by chiral GC-MS analyses and comparisons with an authentic sample of malyngolide seco-acid (4). Compound 1 showed moderate in vitro antimalarial activity against chloroquine-resistant Plasmodium falciparum (W2) (IC(50) = 19 microM) but roughly equivalent toxicity against H-460 human lung cell lines. Furthermore, because the closely related cyanobacterial natural product tanikolide dimer (5) was a potent SIRT2 inhibitor, compound 1 was evaluated in this assay but found to be essentially inactive.

Securing Economic Benefits and Promoting Conservation through Bioprospecting

ABSTRACT Bioprospecting has frequently been cited as a sustainable use of biodiversity. Nevertheless, the level of bioprospecting in biodiversity-rich tropical regions falls below its potential, with the result that bioprospecting has produced only limited economic benefits. We present a bioprospecting program that, in addition to promoting drug discovery, provides economic benefits to and promotes conservation in Panama through the sustainable use of biodiversity. The program was initiated using insights from 20 years of nonapplied ecological research to enhance the likelihood of finding treatments for human disease. Samples are not sent abroad; rather, most of the research is carried out in Panamanian laboratories. Panama has received immediate benefits for the use of its biodiversity in the form of research funding derived from sources outside Panama, training for young Panamanian scientists, and enhanced laboratory infrastructure. Over the long term, discoveries derived from bioprospecting may help to establish research-based industries in Panama.

A facile synthesis of primary amines from carboxylic acids by the curtius rearrangement

Abstract 2-Trimethylsilylethanol was used to trap isocyanates produced by the Curtius rearrangement of acyl azides and the resulting trimethylsilylethyl carbamates were readily cleaved with tetra-n-butylammonium fluoride to liberate the primary amines.

Linking bioprospecting with sustainable development and conservation: the Panama case

The limited international resources for economic aid and conservation can only mitigate poverty and losses of biodiversity. Hence, developing nations must establish the capacity to resolve their problems. Additionally, policy-makers and donors need to obtain scientific input on issues such as global change and ecosystem services. We propose that for nations rich in biodiversity, ecosystem services derived from bioprospecting, or drug discovery, could contribute to economic development. In the case where unstudied samples are shipped abroad for research, the chances of obtaining royalties are infinitesimally small. Therefore developing nations will only realize benefits from bioprospecting through in-country research on their own biodiversity. Policy-makers and donors have failed to appreciate the value of this approach. In order to provide an example of the inherent links between conservation and sustainable economic development, we initiated a drug discovery effort in Panama that emphasizes local benefit. As much of the drug discovery process as possible is conducted in Panamanian laboratories, providing jobs dependent on intact biodiversity and enhancing local research and training. In short, research, plus the spin-offs from research, provide immediate and long-lasting benefits to Panama. The connection between conservation and development has been highlighted in publicity about the project in Panama’s urban media. This provides a constructive alternative to the perception the among the urban populace that economic development inevitably competes with conservation. In summary, our program uses biodiversity to promote human health as well as to support research capacity, economic development and conservation within Panama. The program provides an example of the widely recognized but little developed concept of bioprospecting research as an ecosystem service.

Antiprotozoal Activity Against Plasmodium falciparum and Trypanosoma cruzi of Xanthones Isolated from Chrysochlamys tenuis

Abstract One new prenylated xanthone, 1,5-dihydroxy-3-methoxy-4-isoprenylxanthone (1), along with four previously known prenylated xanthones, ananixanthone (2), 1,3,7-trihydroxy-2,4-diisoprenylaxnthone (3), 8-desoxygartanin (4), and toxyloxanthone A (5), have been isolated from Chrysochlamys tenuis. (Hammel) (Clusiaceae). Compound 1 showed moderate activity (31 ± 9 µM) against a chloroquine-resistant strain of Plasmodium falciparum., and compounds 3 and 5 showed the highest antimalarial potency, IC50 = 20 ± 2 and 16 ± 4 µM, respectively. Evaluated against Trypanosoma cruzi., compound 1 presented negligible activity, but compounds 2, 3, and 4 showed mild antitrypanosomal activity with IC50 values of 23 ± 4, 21 ± 5, and 24 ± 3 µM, respectively. All structures were elucidated by NMR spectroscopy in combination with UV, IR, and MS spectral data.

Antitrypanosomal activity of a novel norlignan purified from Nectandra lineata

Bioactivity-guided fractionation of a MeOH–EtOAc extract from the young leaves of Nectandra lineata (Lauraceae), using a Trypanosoma cruzi bioassay resulted in the isolation of a novel norlignan 3′-methoxy-3,4-methylenedioxy-4′,7-epoxy-9-nor-8,5′-neolignan-9′-acetoxy (1), together with the known compound, 3′-methoxy-3,4-methylenedioxy-4′-7-epoxy-9-nor-8,5′-neolignan-7,8′-diene (2). Compounds 1 and 2 were shown to inhibit the growth of T. cruzi epimastigotes in axenic culture.

Antiprotozoal Activity Against Plasmodium falciparum and Trypanosoma cruzi of Aeroplysinin-1 Isolated from the New Sponge Aplysina chiriquensis

ABSTRACT Crude methanol extracts from the recently discovered sponge, Aplysina chiriquensis. and Aplysina gerardogreeni., collected at the southwest Pacific Coast of Panama, showed moderate antiplasmodial activity. Fractionation of the crude extracts from A.. chiriquensis. led to the isolation of the known dibromotyrosine derivatives 1–5. Compound 3, aeroplysinin-1, displayed antiprotozoal activity against chloroquine-resistant Plasmodium falciparum. and Trypanosoma cruzi.. Comparative analysis by HPLC of the five specimens collected showed the presence of the same metabolites but in different relative proportions. Compounds 1–5 are reported for the first time as constituents of A.. chiriquensis. and A.. gerardogreeni.. This is the first report of the antiprotozoal activity of aeroplysinin-1 (3).