José L. López-Pérez

Synthesis and Antimitotic and Tubulin Interaction Profiles of Novel Pinacol Derivatives of Podophyllotoxins

Several pinacol derivatives of podophyllotoxins bearing different side chains and functions at C-7 were synthesized through reductive cross-coupling of podophyllotoxone and several aldehydes and ketones. While possessing a hydroxylated chain at C-7, the compounds retained their respective hydroxyl group with either the 7α (podo) or 7β (epipodo) configuration. Along with pinacols, some C-7 alkylidene and C-7 alkyl derivatives were also prepared. Cytotoxicities against neoplastic cells followed by cell cycle arrest and cellular microtubule disruption were evaluated and mechanistically characterized through tubulin polymerization inhibition and assays of binding to the colchicine site. Compounds of the epipodopinacol (7β-OH) series behaved similarly to podophyllotoxin in all the assays and proved to be the most potent inhibitors. Significantly, 7α-isopropyl-7-deoxypodophyllotoxin (20), without any hydroxyl function, appeared as a promising lead compound for a novel type of tubulin polymerization inhibitors. Experimental results were in overall agreement with modeling and docking studies performed on representative compounds of each series.

NAPROC-13

MOTIVATION Although natural products represent a reservoir of molecular diversity, the process of isolating and identifying active compounds is a bottleneck in drug discovery programs. The rapid isolation and identification of the bioactive component(s) of natural product mixtures during the bioassay-guided fractionation have become crucial factors in the competition with chemical compound libraries and combinatorial synthetic efforts. In this respect, the use of spectral databases in identification processes is indispensable. RESULTS We have developed a database containing (13)C spectral information of over 6000 natural compounds, which allows for fast identifications of known compounds present in the crude extracts and provides insight into the structural elucidation of unknown compounds. AVAILABILITY http://c13.usal.es

3-Phenylcoumarins as Inhibitors of HIV-1 Replication

We have synthesized fourteen 3-phenylcoumarin derivatives and evaluated their anti-HIV activity. Antiviral activity was assessed on MT-2 cells infected with viral clones carrying the luciferase gene as reporter. Inhibition of HIV transcription and Tat function were tested on cells stably transfected with the HIV-LTR and Tat protein. Six compounds displayed NF-κB inhibition, four resulted Tat antagonists and three of them showed both activities. Three compounds inhibited HIV replication with IC50 values < 25 µM. The antiviral effect of the 4-hydroxycoumarin derivative 19 correlates with its specific inhibition of Tat functions, while compound 8, 3-(2-chlorophenyl)coumarin, seems to act through a mechanism unrelated to the molecular targets considered in this research.

Anti-Trypanosoma activity of some natural stilbenoids and synthetic related heterocyclic compounds

We report the anti-Chagasic activity of the natural dihydrostilbenoid isonotholaenic acid and several simple derivatives, as well as that of some representative compounds of related synthetic series, with basic structures of benzalphthalides, dihydrostilbamides, isoindoles, phthalazin-1-ones, imidazo[2,1-a]isoindoles and pyrimido[2,1-a]isoindoles. The evaluation was performed in vitro on cultures of epimastigote and trypomastigote forms of Trypanosoma cruzi. Some of the tested compounds resulted to be as potent as benznidazole (epimastigotes), and others were shown to be more active than gentian violet (trypomastigotes), used as reference drugs.

Leishmanicidal activity of some stilbenoids and related heterocyclic compounds.

We have evaluated the leishmanicidal activity of some natural and semisynthetic dihydrostilbenoids and several compounds of other series of dihydrostilbamides, isoindoles, phthalazinones, imidazoisoindoles and pyrimidoisoindoles. The evaluation was performed in vitro, on cultures of cutaneous, mucocutaneous and visceral strains of Leishmania spp. The most potent and selective compounds of these series were the dihydrostilbene piperidides.

A New Cytotoxic Friedelane Acid - Pluricostatic Acid - and Other Compounds from the Leaves of Marila pluricostata

Bioassay-guided fractionation of the dichloromethane extract of the leaves of Marila pluricostata led to the isolation of 2α,3β-dihydroxy-D:A-friedoolean-28-oic acid (pluricostatic acid), a new friedelane triterpenoid, (1), ten known triterpenoids and three sterols. Their chemical structures were elucidated through spectroscopic analysis. The less polar fractions, on GC/MS analysis and comparison with a MS library, resulted in the identification of twenty four sesquiterpenoids. The new triterpenoid acid 1 showed cytotoxicity against the MCF-7, H-460, and SF-268 human cancer cell lines with GI50 values from 1.2 to 3.3 μg/mL.

Antimalarial activity of imidazo(2,1-a)isoindol-5-ol derivatives and related compounds

The synthesis of several series of imidazo[2,1-a]isoindol-5-ol derivatives and the results of their evaluation against Plasmodium falciparum are presented and discussed. The effects of electron-withdrawing or-donating substituents on different parts of the molecule, as well as those produced by the incorporation of an additional fused ring, were analyzed. Several compounds showed significant antimalarial activity in vitro with IC(50) values as low as 60 nM and a certain efficacy in vivo by reducing parasitemia in Plasmodium berghei mouse models.

Simple dihydrosphyngosine analogues with potent activity against MDR-Mycobacterium tuberculosis

Fifteen dihydrosphingosine analogues have been synthesized and tested in vitro against Mycobacterium tuberculosis (MTB). Two ether (3 and 4b) and one diamine (8b) derivatives have displayed high mycobactericidal potency, with similar MIC values of 1.25 microg/mL, against the virulent strain H37Rv, as well as against a clinical isolate resistant to the five first-line anti-TB drugs. The three compounds, tested on other eleven cultured MTB strains with different multi-drug-resistance (MDR) patterns, retained their MIC values for most strains, or even lowered it, as in the case of compound 4b, which, assayed on strain No. 332, also resistant to all first-line anti-TB drugs, attained the MIC value of 0.78 microg/mL.

Synthesis, Bioevaluation and Structural Study of Substituted Phthalazin-1(2H)-ones Acting as Antifungal Agents

Twenty-five polysubstituted phthalazinone derivatives were synthesized and tested for their antifungal activity against a panel of pathogenic and clinically important yeasts and filamentous fungi. Among them, the compound 4-(4-chlorobenzyl)-2-methylphthalazin-1(2H)-one (5) exhibited a remarkable antifungal activity against standardised strains of dermatophytes and Cryptococcus neoformans, as well as against some clinical isolates. A physicochemical study performed on compound 5 revealed its conformational and electronic characteristics, providing us with useful data for the future design of novel related antifungal analogues.

Vasoactive effects of different fractions from two Panamanians plants used in Amerindian traditional medicine

ETHNOPHARMACOLOGICAL RELEVANCE Cecropia obtusifolia (Cecropiaceae) and Psychotria poeppigiana (Synonym: Cephaelis elata, Rubiaceae) are two Latin American plants broadly used in traditional Amerindian medicine. The former, together with many other species of the genus Cecropia, share the folk reputation of curing heart failure, cough, asthma and bronchitis. The latter is used in Panama by Kuna and Ngäbe Buglé (Guaymies) native Indians for the treatment of dyspnea. AIM OF THE STUDY Based on screening of selected medicinal Panamanian plants by radioligand-binding techniques by Caballero-George et al. (2001), the present study was carried out in order to investigate the vasoactive effects of different fractions from both P. poeppigiana and C. obtusifolia on rat thoracic aorta and identify active fractions and their chemical constituents. MATERIALS AND METHODS Both acid and neutral methanol fractions (P-AMeOH and P-NMeOH) and acid and neutral dichlorometane fractions (P-ADCM and P-NDCM) were obtained from P. poeppigiana crude methanolic and dichlorometane extracts, respectively. Identical fractionation was carried out for C. obtusifolia (C-AMeOH, C-NMeOH, C-ADCM and C-NDCM. Vasorelaxant effect of all fractions, and their inhibition of contractile responses to angiotensin II were evaluated in isolated aortic rings. RESULTS P-AMeOH, P-NMeOH and P-ADCM fractions induced a concentration-dependent relaxation (43.9+/-1.8%, 35.3+/-4.7% and 52.9+/-3.5%, respectively) in the endothelium-intact aorta precontracted by phenylephrine (PE, 10(-6)M). The relaxation produced by C-AMeOH and C-NMeOH (57.3+/-2.5% and 53.3+/-3.3%, respectively) was greater than the effect produced by C-ADCM and C-NDCM (42.2+/-3.4% and 21.8+/-0.8%, respectively). Only the incubation of the aortic rings with P-AMeOH reduced the maximum contraction induced by angiotensin II at 20.08+/-0.55%. CONCLUSIONS The direct vasorelaxation effect observed could explain in part the ethnomedical use of these plants in Amerindian traditional medicine. The most active fractions contain phenolic and aromatic acid compounds. Furthermore, P-AMeOH, the only fraction that showed both vasorelaxant effect and inhibition of contractile responses to angiotensin II, is the most rich in aromatic acids compounds and the only one that contains scopoletin.