Jairo Saez

Antitumor and Antiviral Activity of Colombian Medicinal Plant Extracts

Extracts of nine species of plants traditionally used in Colombia for the treatment of a variety of diseases were tested in vitro for their potential antitumor (cytotoxicity) and antiherpetic activity. MTT (Tetrazolium blue) and Neutral Red colorimetric assays were used to evaluate the reduction of viability of cell cultures in presence and absence of the extracts. MTT was also used to evaluate the effects of the extracts on the lytic activity of herpes simplex virus type 2 (HSV-2). The 50% cytotoxic concentration (CC50) and the 50% inhibitory concentration of the viral effect (EC50) for each extract were calculated by linear regression analysis. Extracts from Annona muricata, A. cherimolia and Rollinia membranacea, known for their cytotoxicity were used as positive controls. Likewise, acyclovir and heparin were used as positive controls of antiherpetic activity. Methanolic extract from Annona sp. on HEp-2 cells presented a CC50 value at 72 hr of 49.6x10(3)mg/ml. Neither of the other extracts examined showed a significant cytotoxicity. The aqueous extract from Beta vulgaris, the ethanol extract from Callisia grasilis and the methanol extract Annona sp. showed some antiherpetic activity with acceptable therapeutic indexes (the ratio of CC50 to EC50). These species are good candidates for further activity-monitored fractionation to identify active principles.

Coumarins from Galipea panamensis and Their Activity against Leishmania panamensis

Two new coumarin compounds (1 and 2), phebalosin (3), its derived artifact murralongin (4), and murrangatin acetonide (5) were isolated from the leaves of Galipea panamensis. The structures of 1 and 2 were assigned as 7-{[(2R*)-3,3-dimethyloxiran-2-yl]methoxy}-8-[(2R*,3R*)-3-isopropenyloxiran-2-yl]-2H-chromen-2-one and 7-methoxy-8-(4-methyl-3-furyl)-2H-chromen-2-one, respectively, on the basis of their spectroscopic data (primarily NMR and MS). Compounds 1-3 were tested against axenic amastigote forms of Leishmania panamensis and displayed 50% effective concentrations (EC(50)) of 9.9, 10.5, and 14.1 microg/mL, respectively. These three compounds also displayed cytotoxicity (IC(50)) at concentrations of 9.7, 33.0, and 20.7 microg/mL, respectively, on human promonocytic U-937 cells.

Five new steroids from Solanum nudum

Abstract Five new steroids, the cholest-4-ene-3,22-diones: tumacone A ( 1 ), tumacone B ( 2 ), tumacoside A ( 3 ), tumacoside B ( 4 ), and a furostenone: tumaquenone ( 5 ), besides diosgenone ( 6 ), were isolated from the aerial parts of Solanum nudum . Their structures were determined by 2D NMR, MS analyses and chemical correlations. Steroid 3 and 5 displayed in vitro antimalarial activity against a Plasmodium falciparum chloroquine-resistant FCB-1 strain (IC 50 27 and 16 μM). The observed stereodependent cyclization into spiroketals of two 16-O isomers is discussed.

Structure-activity relationship in the interaction of substituted perinaphthenones with Mycosphaerella fijiensis.

The levels of native fungitoxic perinaphthenone phytoalexins in susceptible Musa varieties (banana), which are commercially grown in large plantations, are too low to provide plants with long-lasting protection against highly pathogenic fungi. Novel strategies for plant protection are necessary to reduce crop losses and to prevent the development of resistant fungal strains. The synthesis of novel fungicides based on the structures of perinaphthenone natural products is considered to be a promising strategy. Thirteen substituted perinaphthenones, among them two known natural products (1, 2) and 11 synthetics (3-13), were evaluated for their activity against Mycosphaerella fijiensis , and their half-maximal inhibitory concentrations (IC(50)) were calculated to establish structure-activity relationships (SAR). A SAR trend was hypothesized, leading to the design of a new compound, 4-methoxy-2-nitro-1H-phenalen-1-one (14); the new compound displayed significantly enhanced in vitro activity against M. fijiensis compared to other perinaphthenone derivatives. The activity of 14 was comparable to that of two commercial fungicides.

10-Oximeguanacone, the first nitrogenated acetogenin derivative found to be a potent inhibitor of mitochondrial complex I

A new 10-keto bis-tetrahydrofuran acetogenin, guanacone (1), has been isolated from a cytotoxic extract of Annona aff. spraguei seeds. The 10-oximeguanacone derivative 1f is the first bioactive nitrogenated acetogenin found to be a very potent inhibitor of complex I. In addition, a SAR study of guanacone analogues is reported based on the titration of the NADH oxidase and NADH:ubiquinone oxidoreductase activities.

Antiprotozoal 6-Substituted-5,6-Dihydro-a-Pyrones from Raimondia CF. Monoica

Dichloromethane extracts of both the roots and the leaves of Raimondia cf. monoica showed in vitro antiplasmodial and leishmanicidal activities against Plasmodium falciparum and Leishmania panamensis, respectively. Three 6-substituted 5,6-dihydro-2H-pyran-2-ones were isolated. (1) and (2) were identified as (6S)-(5′-oxohepten-1′E,3′E-dienyl)-5,6-dihydro-2H-pyran-2-one (1) and (6R)-(5′-oxohepten-1′Z,3′E-dienyl)-5,6-dihydro-2H-pyran-2-one (2), respectively. (-)-Argentilactone (3) was also isolated. The structure of the new compound (1) was determined by spectroscopic methods; additional spectroscopic data for (2) are reported for the first time.

Effect of Solanum nudum steroids on uninfected and Plasmodium falciparum-infected erythrocytes

Steroids from Solanum nudum (SNs) have demonstrated antiplasmodial activity against erythrocytic stages of the Plasmodium falciparum strain FCB-2. It is well known that steroids can alter the membrane function of erythrocytes. Thus, we assessed alterations in the membranes of uninfected red blood cells, the parasite invasiveness and the solute-induced lysis of parasitised red blood cells (pRBCs). induced by SNs. We found that most merozoites were unable to invade SN-treated erythrocytes. However, transmission electron microscopy revealed no effect on the morphology of uninfected erythrocytes treated with either SN2 or diosgenone and neither SN induced haemolysis of uninfected erythrocytes. SN2 and SN4 inhibited isosmotic sorbitol and alanine-induced haemolysis of pRBCs. In contrast, diosgenone and SN1 did not inhibit solute-induced haemolysis. The inhibition of solute-induced lysis of parasitised erythrocytes by SN2 and SN4 suggest an action of these SNs on new permeability pathways of pRBCs.

Plasmodium falciparum: Effect of Solanum nudum steroids on thiol contents and β-hematin formation in parasitized erythrocytes

We studied the effects on total thiols glutathione (GSH) and cysteine contents in Plasmodium falciparum in vitro when treated with four steroid derivatives and a sapogenin (Diosgenone) extracted from Solanum nudum. We also determined their capacity to inhibit beta-hematin formation. We showed that SN-1 (16alpha-acetoxy-26-hydroxycholest-4-ene-3,22-dione) increased total glutathione and cysteine concentrations while SN-4 (26-O-beta-d-glucopyranosyloxy-16alpha-acetoxycholest-4-ene-3,22-dione) decreased the concentration of both thiols. Acetylation in C16 was crucial for the effect of SN-1 while type furostanol and terminal glucosidation were necessary for the inhibitory properties of SN-4. The combination of steroids and buthionine sulfoximine, a specific inhibitor of a step-limiting enzyme in GSH synthesis, did not modify the glutathione contents. Finally, we found that SN-1 inhibited more than 80% of beta-hematin formation at 5.0mM, while the other steroids did not show any effect.

Tripoxyrollin, a New Epoxy Acetogenin from the Seeds of Rollinia membranacea 1

Abstract A new epoxy acetogenin, tripoxyrollin (1), has been isolated from the seeds of the Colombian Annonaceae, Rollinia membranacea. Its structure was elucidated on the basis of spectral data. Biomimetic synthesis of isodesacetyluvaricin (2) from tripoxyrollin (1) suggests its key role in the biogenesis of the adjacent bis-tetrahydrofuran acetogenins.

A CONVENIENT, RENEWABLE SOURCE OF THE ANXIOLYTIC PROAPORPHINE ALKALOID GLAZIOVINE: DUGUETIA VALLICOLA LEAVES

The leaves of Duguetia vallicola, a fairly common, large evergreen tree from the coastal regions of Panama, Colombia and Venezuela, contain (6aS)-glaziovine (1) as a major constituent. The abundance and renewable character of the plant material make it an attractive source for this rare, psychoactive alkaloid. The availability of glaziovine and its O-methyl derivative pronuciferine (2) has made complete 1H and 13C NMR assignments of proaporphines possible for the first time