Luis Cubilla-Rios

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.

Antileishmanial Constituents of the Panamanian Endophytic Fungus Edenia sp.

Bioassay-directed fractionation of extracts from the fermentation broth and mycelium of the fungus Edenia sp. led tothe isolation of five antileishmanial compounds, preussomerin EG1 (1), palmarumycin CP2 (2), palmarumycin CP17 (3), palmarumycin CP18 (4), and CJ-12,371 (5). Compounds 3 and 4 are new natural products, and this is only the second report of compound 1. The structures of compounds 1-5 were established by spectroscopic analyses (HRMS and NMR). All metabolites caused significant inhibition of the growth of Leishmania donoVani in the amastigote form, with IC50 values of 0.12, 3.93, 1.34, 0.62, and 8.40 microM, respectively. Compounds 1-5 were inactive when tested against Plasmodium falciparum or Trypanasoma cruzi at a concentration of 10 microg/mL, indicating that they have selective activity against Leishmania parasites. Compounds 1-5 showed weak cytotoxicity to Vero cells (IC50 of 9, 162, 174, 152, and 150 microM, respectively); however, the therapeutic window of these compounds is quite significant with 75, 41, 130, 245, and 18 times (respectively) more antileishmanial activity than cytotoxicity.

Mycoleptodiscins A and B, cytotoxic alkaloids from the endophytic fungus Mycoleptodiscus sp. F0194.

Two novel reddish-orange alkaloids, mycoleptodiscin A (1) and mycoleptodiscin B (2), were isolated from liquid cultures of the endophytic fungus Mycoleptodiscus sp. that had been isolated from Desmotes incomparabilis in Panama. Elucidation of their structures was accomplished using 1D and 2D NMR spectroscopy in combination with IR spectroscopic and MS data. These compounds are indole-terpenes with a new skeleton uncommon in nature. Mycoleptodiscin B (2) was active in inhibiting the growth of cancer cell lines with IC50 values in the range 0.60-0.78 μM.

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.

Domestication Syndrome in Caimito (Chrysophyllum cainito L.): Fruit and Seed Characteristics

Domestication Syndrome in Caimito (Chrysophyllum cainitoL.): Fruit and Seed Characteristics: The process of domestication is understudied and poorly known for many tropical fruit tree crops. The star apple or caimito tree (Chrysophyllum cainito L., Sapotaceae) is cultivated throughout the New World tropics for its edible fruits. We studied this species in central Panama, where it grows wild in tropical moist forests and is also commonly cultivated in backyard gardens. Using fruits collected over two harvest seasons, we tested the hypothesis that cultivated individuals of C. cainito show distinctive fruit and seed characteristics associated with domestication relative to wild types. We found that cultivated fruits were significantly and substantially larger and allocated more to pulp and less to exocarp than wild fruits. The pulp of cultivated fruits was less acidic; also, the pulp had lower concentrations of phenolics and higher concentrations of sugar. The seeds were larger and more numerous and were less defended with phenolics in cultivated than in wild fruits. Discriminant Analysis showed that, among the many significant differences, fruit size and sugar concentration drove the great majority of the variance distinguishing wild from cultivated classes. Variance of pulp phenolics among individuals was significantly higher among wild trees than among cultivated trees, while variance of fruit mass and seed number was significantly higher among cultivated trees. Most traits showed strong correlations between years. Overall, we found a clear signature of a domestication syndrome in the fruits of cultivated caimito in Panama.ResumenSíndrome de domesticación en caimito (Chrysophyllum cainito L): Características de las frutas y semillas: El proceso de domesticación de muchos árboles frutales tropicales es poco estudiado y entendido. El caimito (Chrysophyllum cainito L., Sapotaceae) es cultivado, por su fruto comestible, en todas las regiones tropicales de América. Hemos estudiado esta especie en Panamá central, donde crece en huertos caseros y en poblaciones silvestres del bosque húmedo tropical. Usando frutos colectados en dos años de cosecha, probamos la hipótesis de que las semillas y los frutos de individuos cultivados e individuos silvestres de C. cainito tienen características distintas debido a la domesticación. Encontramos que los frutos de los individuos cultivados fueron significativa y sustancialmente más grandes , con mayor cantidad de pulpa y menos exocarpo que los frutos de individuos silvestres. La pulpa de la fruta de los individuos cultivados fue menos ácida, con menor concentración de compuestos fenólicos y alta concentración de azúcares. Las semillas fueron más grandes, numerosas y con menor autodefensas (compuestos fenólicos) en los individuos cultivados que en los silvestres. El análisis discriminante mostró, entre muchas diferencias significativas, que el tamaño de la fruta y la concentración de azucares fueron los factores más importantes para discriminir entre individuos cultivados y silvestres. La varianza entre individuos fue significativamente mayor dentro de los árboles silvestres que dentro de los árboles cultivados, para los compuestos fenólicos de la pulpa. En contraste, la varianza fue significativamente mayor entre árboles cultivados para el peso de la fruta y número de semillas. La mayoría de las características demostraron una fuerte correlación entre años. En general, encontramos un patrón claro para el síndrome de la domesticación en la fruta de caimito en Panamá.

Activity against Plasmodium falciparum of Lactones Isolated from the Endophytic Fungus Xylaria sp.

Three lactones were isolated from the culture medium of the endophytic fungus Xylaria sp. Grev. (Xylariaceae). The major compound, which showed weak activity (13 μ g/mL) against a chloroquine-resistant strain of Plasmodium falciparum, was identified as (+)-phomalactone (1). The others were 6-(1-propenyl)-3,4,5,6-tetrahydro-5-hydroxy-4H-pyran-2-one (2) and 5-hydroxymellein (3). Compounds 1 and 2 are reported for the first time as constituents of Xylaria. Also, this is the first report of the activity of the compounds 1–3 against a chloroquine-resistant Plasmodium falciparum strain.

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.

Antiprotozoal Activity of Flavonoid Glycosides Isolated from Clidemia sericea. and Mosquitoxylon jamaicense.

Abstract A new O.-galloyl-C-glycosylflavone, 2″,6″-O.-digalloylvitexin (1), along with four known glycosylflavones (2–5) have been isolated from Clidemia sericea. D. Don (Melastomataceae), and four other known glycosylflavones (6–9) have been isolated from Mosquitoxylon jamaicense. Krug & Urb. (Anacardiaceae). Compound 1, 3, and 6 showed mild antimalarial activity (24 ± 1, 38 ± 2, and 44 ± 1 µM, respectively) against a chloroquine-resistant P. falciparum. strain. Additionally, tests against leishmaniasis and Trypanosoma cruzi. were made. These compounds were identified by MS, UV, IR, and 1D and 2D NMR data and by comparison with the literature data.

Screening and evaluation of antiparasitic and in vitro anticancer activities of Panamanian endophytic fungi

Many compounds produced by fungi have relevant pharmaceutical applications. The purpose of this study was to collect and isolate endophytic fungi from different regions of Panama and then to test their potential therapeutic activities against Leishmania donovani, Plasmodium falciparum, and Trypanosoma cruzi as well as their anticancer activities in MCF-7 cells. Of the 25 fungal isolates obtained, ten of them had good anti-parasitic potential, showing selective activity against L. donovani; four had significant anti-malarial activity; and three inhibited the growth of T. cruzi. Anticancer activity was demonstrated in four isolates. Of the active isolates, Edenia sp. strain F0755, Xylaria sp. strain F1220, Aspergillus sp. strain F1544, Mycoleptodiscus sp. strain F0194, Phomopsis sp. strain F1566, Pycnoporus sp. strain F0305, and Diaporthe sp. strain F1647 showed the most promise based on their selective bioactivity and lack of toxicity in the assays.