Teresa A. Grillo

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

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 .

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.

Light- and singlet oxygen-mediated antifungal activity of phenylphenalenone phytoalexins.

The light-induced singlet oxygen production and antifungal activity of phenylphenalenone phytoalexins isolated from infected banana plants (Musa acuminata) are reported. Upon absorption of light energy all studied phenylphenalenones sensitise the production of singlet oxygen in polar and non-polar media. Antifungal activity of these compounds towards Fusarium oxysporum is enhanced in the presence of light. These results, together with the correlation of IC50 values under illumination with the quantum yield of singlet oxygen production and the enhancing effect of D2O on the antifungal activity, suggest the intermediacy of singlet oxygen produced by electronic excitation of the phenylphenalenone phytoalexins.

Phototoxic Phytoalexins. Processes that Compete with the Photosensitized Production of Singlet Oxygen by 9-Phenylphenalenones †

Abstract Experiments were performed to elucidate the excited-state behavior of 9-phenylphenalenones, which are phototoxic plant secondary metabolites involved in mechanisms of light-mediated plant defense. Using a combination of time-resolved and steady-state UV/visible spectroscopies, time-resolved IR absorption spectroscopy, time-resolved singlet oxygen phosphorescence measurements and cyclic voltammetry, we provide evidence of an intramolecular charge-transfer process in the excited singlet and the triplet states of 9-phenylphenalenones that modulates the photosensitized production of singlet oxygen.

Diterpenes from the aerial part of Salvia columbariae

The new diterpenes 11,12-di-O-methylrosmanol and 11,12-di-O-methylcarnosol, together with the known compounds carnosic acid, carnosol, rosmanol, epirosmanol, isorosmanol, salvicanol and rosmadial were isolated from the aerial part of Salvia columbariae. The structures of the new diterpenes were established from their spectral data and by chemical correlations. The co-occurence of all these compounds in a single species provides further support of our previously postulated biogenetic pathway to highly oxidized abietatriene compounds involving enzymatic dehydrogenation processes and the participation of singlet oxygen.

Sesquiterpene lactones from Salvia palaefolia

Abstract The aerial part of Salvia palaefolia yielded (−)-glechomafuran, 1β,10α;4α,5β-diepoxy-8β-hydroxyglechoman-8α,12-olide and the new eudesmanolides: 1α-acetoxy-8α-hydroxy-2-oxo-eudesman-3,7(11)-dien-8,12-olide and 1α,8α-dihydroxy-2-oxo-eudesman-3,7(11)-dien-8,12-olide. The structure of the former new compound was determined from its spectral data and chemical behaviour and its absolute configuration by CD experiments. The absolute configuration of 1β,10α;4α,5β-diepoxy-8β-hydroxyglechoman-8α,12-olide was established by X-ray diffraction analysis.