Javier G. Luis

Fungus-Elicited Metabolites from Plants as an Enriched Source for New Leishmanicidal Agents: Antifungal Phenyl-Phenalenone Phytoalexins from the Banana Plant (Musa acuminata) Target Mitochondria of Leishmania donovani Promastigotes

ABSTRACT Two antifungal phenyl-phenalenone phytoalexins isolated from the banana plant (Musa acuminata) elicited with the fungus Fusarium oxysporum, together with a methoxy derivative of one of them and two epoxide precursors of their chemical synthesis, were tested for leishmanicidal activity on Leishmania donovani promastigotes and L. infantum amastigotes. Drugs inhibited proliferation of both forms of the parasite with a 50% lethal concentration range between 10.3 and 68.7 μg/ml. Their lethal mechanism was found linked to the respiratory chain by a systematic approach, including electron microscopy, measurement of the oxygen consumption rate on digitonin-permeabilized promastigotes, and enzymatic assays on a mitochondrial enriched fraction. Whereas the whole set of compounds inhibited the activity of fumarate reductase in the mitochondrial fraction (50% effective concentration [EC50] between 33.3 and 78.8 μg/ml) and on purified enzyme (EC50 = 53.3 to 115 μg/ml), inhibition for succinate dehydrogenase was only observed for the two phytoalexins with the highest leishmanicidal activity: anigorufone and its natural analogue 2-methoxy-9-phenyl-phenalen-1-one (EC50 = 33.5 and 59.6 μg/ml, respectively). These results provided a new structural motif, phenyl-phenalenone, as a new lead for leishmanicidal activity, and support the use of plant extracts enriched in antifungal phytoalexins, synthesized under fungal challenge, as a more rational and effective strategy to screen for new plant leishmanicidal drugs.

Diterpenes from Salvia mellifera and their biogenetic significance

Abstract The new diterpenes, 11,12-dihydroxy-20-nor-abieta-5(10),8,11,13-tetraen-1-one and isogaldosol, together with the known compounds carnosic acid, carnosol, rosmanol, rosmadial, galdosol and isorosmanol were isolated from the aerial part of Salvia mellifera . The structures of the new diterpenes were established from their spectral data and by chemical correlations. The co-occurrence of all these compounds in one species taken together with their chemical behaviour led to the postulation of a biogenetic pathway to highly oxidized abietatriene diterpenes in which enzymatic dehydrogenation processes and the participation of singlet-state oxygen appear to play an important role.

Chromenes from Ageratum conyzoides

Abstract-Analysis of the aerial part of Ayeratum conyzoides afforded 11 chromenes, sitosterol, (+)-sesamin and caryophyllene oxide. One chromene is new and eight of the others were obtained for the first time from this species. The ‘C NMR spectral data for four of the chromenes have not been published before. INTRODUCIION Over the last two or three decades, great attention has been focused on the biological activity of natural com- pounds of plant origin for their potential as natural pesticides against phytophagous insects. In Colombia, plants have been used for centuries for their insecticidal. repellent or antifeedant properties in the protection of crops from insect attack [I]. Ageratum conyzoides, a widespread weed in Colombia and elsewhere, known to contain precocene I and precocene II [2,3], has been used both in folk medicine and as an insecticide. A study of the insecticidal activity of various fractions of an n-hexane extract of

Diterpenes from the roots of Salvia canariensis

Abstract The new diterpenes, deoxocarnosol 12-methyl ether, salvicanol and 6α-hydroxydemethylcryptojaponol, and the known ones, sugiol and demethylcryptojaponol, have been isolated from the bark of the roots of Salvia canariensis .

Musanolones : four 9-phenylphenalenones from rhizomes of Musa acuminata

Abstract Four new phenalenone-type phytoalexins, named musanolones C-F, have been isolated from infected rhizomes of banana plants (Musa acuminata; AAA cultivar Grand Nain). These phytoalexins were biosynthesized de novo by the plants upon infection by Fusarium oxysporum f. sp. cubense race 4, Panamas disease causal agent. The structures of the new phytoalexins were elucidated using spectroscopic data and chemical correlations. Hydroxyanigorufone has been previously described as a constitutive natural product, from Anigozanthos rufus, but it was never described as a phytoalexin. The chemical shift for all of the hydrogen and carbon atoms in the musanolones C-F were unambiguously established by mono- and bi-dimensional, homo- and hetero-nuclear NMR experiments (1H NMR, 13C NMR, COSY, HMQC and HMBC). Preliminary in vitro assays of all the musanolones tested until now show a strong inhibitory activity on the growth of the germination tube of F. oxysporum f. sp. cubense race 4.

Phenalenone-type phytoalexins from Musa acuminata. Synthesis of 4-phenyl-phenalenones

Abstract Two new 4-phenyl-phenalenone-type phytoalexins ( 2 , 3 ) have been isolated from rhizomes of Musa acuminata infected with the fungus Fusarium oxysporum . The structures of the new phytoalexins were elucidated on the basis of spectroscopic evidence, chemical correlation and synthesis from commercial phenalen-1-one. The chemical shift for all of the hydrogen and carbon atoms in the substances were unambiguously established by mono- and bidimensional, homo- and heteronuclear NMR experiments ( 1 H NMR, 13 C NMR, COSY, HMQC and HMBC). In preliminary “in vitro” assays, the new phytoalexins have shown inhibitory activity on the growth of the germinative tube of Fusarium oxysporum f. sp. cubense race 4 .

Structure—antimicrobial activity relationships of abietane diterpenes from Salvia species

Abstract Twenty-one abietatriene diterpenes isolated from Salvia species were evaluated for antimicrobial activity against three strains of bacteria and one yeast. The results obtained show that the free catechol grouping is essential for antimicrobial activity against Gram-positive bacteria and that activity appears to be independent of the closing position of the lactone group in the class A compounds. If there was an extra hydroxyl group at C-6 or C-7, activity was reduced to less than a third, and a hydroxy-methylene group at C-16 also rendered the products ineffective. Compounds where the catechol grouping had been oxidized to a quinone exhibited enhanced activity.

Intermediates with biosynthetic implications in de novo production of phenyl-phenalenone-type phytoalexins by Musa acuminata. Revised structure of emenolone

Abstract Three new intermediates ( 1 – 3 ) in de novo biosynthetic pathway to phenyl-phenalenone-type phytoalexins have been isolated from rhizomes of Musa acuminata infected with the fungus Fusarium oxysporum . The structures of the new pre-phytoalexins were elucidated on the basis of spectroscopic evidences, chemical correlation and acid catalyzed biomimetic cyclization of 1 to emenolone ( 4 ), isolated from the same source and whose previously reported structure has been unambiguously corrected by X-ray diffraction analysis. The chemical shift for all of the hydrogen and carbon atoms in the substances were unambiguously established by mono- and bidimensional, homo- and heteronuclear NMR experiments ( 1 H NMR, 1 3C NMR, COSY, ROESY, HMQC and HMBC).

Diterpenes and diterpene quinones from the roots of Salvia apiana

Abstract The new natural diterpenes, 6,7-didehydroferruginol, 6,7-didehydrosempervirol, 16-hydroxy-6,7-didehydroferruginol, 11,12,16-trihydroxy-20(10 → 5)abeo-abieta-1(10),6,8,11,13-pentaene, the diterpene quinones, 16-hydroxyroyleanone and 6-deoxo-5,6-didehydrolanugon Q plus the known compounds ferruginol, miltiodiol, cryptotanshinone, lanugon Q and salvicanol were isolated from the roots of Salvia apiana . Their structures were established by spectrometry. The co-occurrence of so many abietane diterpenes with different degrees of oxidation and modified skeletons is in accordance with the biosynthetic route previously proposed for these compounds.

Methoxyflavones from Ageratum conyzoides

Abstract Nine methoxyflavones were obtained from aerial parts of Ageratum conyzoides , two of which are new: 5,6,8,3′,4′,5′-hexamethoxyflavone and 8-hydroxy-5,6,7,3′,4′,5′-hexamethoxyflavone.