Pablo N. Solis

Screening of plant extracts for antiprotozoal and cytotoxic activities.

Methanolic and aqueous extracts derived from 43 plant species, selected either from ethnobotanical or chemotaxonomical data, were screened for their antiprotozoal activity against Leishmania donovani and Trypanosoma brucei brucei. The cytotoxic activity against KB cells was also determined. Eight extracts had IC50 values of less than 10 microg/ml against Leishmania donovani. The most active was Triclisia patens with an IC50 value of 1.5 microg/ml against Leishmania donovani. Annona purpurea and Alstonia macrophylla had IC50 values below 10 microg/ml against Trypanosoma brucei brucei. Annona purpurea was the most cytotoxic against KB cells.

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.

Medicinal plant inventory of Kuna Indians: Part 1

Results of an ethnopharmacognostic survey of 90 plants used by the Kuna Indians of San Blas Islands, who live in Ailigandí, are listed. Results of a literature search are also reported, including medical uses, known constituents and pharmacological effects.

Flavonol glycosides fromMonnina sylvatica

Abstract A new kaempferol triglycoside and three known kaempferol glycosides, among them two apiosides, have been isolated from the aerial parts ofMonnina sylvatica. The structures were established on the basis of acid and enzymatic hydrolysis and spectral data (UV,1H and13C NMR, NOE difference measurements, D/CI and FAB-MS) of the isolates and of some derivatives. The triglycoside kaempferol 3-O-β- d -glucosyl-(1→2)-O-[α- l -rhamnosyl(1→6)]-β- d galactoside is a new natural product. The configuration of the apiosyl moiety in kaempferol 3-O-β- d -apiosyl(1→2)β- d -galactoside kaempferol 3-O-β- d -apiosyl(1→2)-O-[α- l -rhamnosyl(1→6)]-β- d -galactoside was established through NOE difference measurements on the peracetate.

Screening of Latin American Plants for Cytotoxic Activity

Abstract The SRB cytotoxicity assay was used to screen plant extracts, in a collaborative multinational OAS project involving Argentina, Bolivia, Colombia, Costa Rica, Guatemala, Nicaragua and Panama, against breast (MCF-7), lung (H-460), and central nervous system (SF-268) human cancer cell lines. Out of 310 species tested, 23 (7.4%) plants showed cytotoxic activity at GI50 values ≤10 µg/ml. The most active plants were Thevetia ahouai., Physalis viscosa., Piper jacquemontianum., Piper barbatum., Senna occidentalis., Tovomita longifolia., and Lippia cardiostegia.. Blepharocalyx salicifolius. and Senna occidentalis. were selectively active against one cell line, SF-268 or MCF-7, respectively. Within the framework of this project, 14 compounds have been isolated, 5 new (4 benzophenones, coumarin) and 9 known to the literature. But only the bioassay-guided fractionation of the active extract of Piper barbatum. leaves, which led to the isolation of three known compounds: (2′E., 6′E.)-2-farnesyl-1,4-benzoquinone (1), (2′E., 6′E.)-2-farnesylhydroquinone (2), and dictyochromenol (3), is reported here. The chemical structures of 1 and 2 were determined by spectral means (1D, 2D NMR, MS) and chemical data. Among these three, (2′E., 6′E.)-2-farnesyl-1,4-benzoquinone was the most active (MCF-7 GI50 = 1.8 µg/ml; H-460 GI50 = 4.8 µg/ml; SF-268 GI50 = 3.5 µg/ml).

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.

Quinoline alkaloids from Psychotria glomerulata

Abstract Three new quinoline alkaloids have been isolated from the aerial parts of Psychotria glomerulata from Panama. The major alkaloid, glomerulatine A, was identified as 8-8a,8′-8′ a tetradehydro(−)-calycanthine on the basis of spectral data including 1 H, 13 C, COSY-45, HMBC, HMQC and ROESY techniques. Computerized 1 H NMR analysis was used to establish that glomerulatine A possessed the calycanthine- and not the iso-calycanthine-type structure. Two minor alkaloids, glomerulatines B and C, were also isolated and on the basis of spectroscopic evidence it is proposed that they are 8-8a,8′-8′a-tetrahydro-N′-demethyl(−)-calycanthine and 8-8a-didehydro-(−)-calycanthine, respectively.

Alkaloids from Cephaelis dichroa

Abstract A new indole alkaloid, vallesiachotamine lactone, and four known compounds strictosidine, strictosamide, vallesiachotamine and angustine were isolated from the aerial parts of Cephaelis dichroa. Structures were established by spectroscopic methods (UV, IR, mass spectrometry, 1H and 13C NMR, including COSY 45 and 1H13C heterocorrelation). Isovallesiachotamine was detected as a degradation product of vallesiachotamine.

Screening of Latin American plants for antiparasitic activities against malaria, Chagas disease, and leishmaniasis.

In order to explore rationally the medical potential of the plant biodiversity of the Central and South American region as a source of novel antiparasitic molecules, a multinational Organization of American States (OAS) project, which included the participation of multidisciplinary research centers from Argentina, Bolivia, Colombia, Costa Rica, Guatemala, Nicaragua and Panama, was carried out during the period 2001-2004. This project aimed at screening organic plant extracts for antitrypanosomal, antileishmanial and antimalarial activities and subsequently isolating and characterizing bioactive molecules. Plants for antiparasitic screening were selected from a database of ethnomedical uses of Latin American plants (PlanMedia) based on the amount of biological and chemical information available in the literature. We report here the evaluation of 452 extracts from 311 plant species in vitro screens against Plasmodium falciparum, Leishmania mexicana, and Trypanosoma cruzi. Out of 311 species tested, 17 plants (5.4%) showed antiparasitic activities at IC50 values ≤ 10 µg/mL. The most active plants were Acnistus arborescens (L.) Schltdl. (Solanaceae) (leaf, EtOH, IC50: 4 µg/mL) Monochaetum myrtoideum Naudin (Melastomataceae) (leaf, MeOH, IC50: 5 µg/mL) and Bourreria huanita (Lex.) Hemsl. (Boraginaceae) (branch, EtOH, IC50: 6 µg/mL). These were selectively active against P. falciparum, L. mexicana and T. cruzi, respectively.

A New Larvicidal Lignan from Piper fimbriulatum

Abstract A new lignan, 3,4,5′-trimethoxy-3′,4′-methylenedioxy-7,9′:7′,9 diepoxylignan (1) (6-[4-(3,4-dimethoxy-phenyl)-tetrahydro-furo[3,4-c.]furan-1-yl]-4-methoxy-benzo[] dioxole) together with two known lignans, 7′-epi.-sesartemin (2) and diayangambin (3), and a known flavonoid, 5-hydroxy-7,4′-dimethoxyflavone (4), were isolated from the leaves of Piper fimbriulatum. C. DC. Their structures were assigned by a combination of one- and two-dimensional NMR techniques. 7′-epi.-Sesartemin (2) showed the highest larvicidal activity against Aedes aegypti. (LC100 17.6 µg/ml) and weak antiplasmodial (IC50 7.0 µg/ml) and antitrypanosomal (IC50 39.0 µg/ml) activities. None of the compounds was active against Leishmania mexicana..