Winston Quiñones

Passifloricins, polyketides α-pyrones from Passiflora foetida resin.

Abstract Three polyketides α-pyrones, named passifloricins, were isolated from Passiflora foetida resin; their structures and relative configurations were assigned through 2D NMR spectroscopic analyses. These types of compounds were not detected in other passion flowers.

Phytoalexin Accumulation in Colombian Bean Varieties and Aminosugars as Elicitors

The accumulation of isoflavonoid phytoalexins was studied in several Colombian bean cultivars resistant and susceptible to Colletotrichum lindemuthianum fungus, the causal agent of anthrachnose disease. A time-course accumulation analysis on seedlings treated with CuCl2 showed that phaseollin production was higher in resistant cultivars than in susceptible ones. Also, a defensive role of phytoalexins was demostrated when extracts containing this pterocarpan exhibited antifungal activity against C. lindemuthianum. In addition, the elicitor activity of some aminosugars was also established.

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.

ERMANIN : AN INSECT DETERRENT FLAVONOID FROM PASSIFLORA FOETIDA RESIN

Abstract Ten flavonoids were isolated from Passiflora foetida L. resin. One of them, ermanin, has a high deterrent activity at 40 ppm against Dione juno larvae.

Synthesis and Antifungal Activity of Musa Phytoalexins and Structural Analogs

Winston Quinones, Gustavo Escobar, Fernando Echeverri *, Fernando Torres, Yoni Rosero,Vi ctor Arango, Gloria Cardona and Adriana GallegoDepartment of Chemistry, Universidad de Antioquia, P. O. Box 1226, Medellin, ColombiaTel.: (57+4)2105658, Fax: (57+4)2330120, E-mail: echeveri@catios.udea.edu.coReceived : 18 January 2000 ; revised form 14 July 2000 / Accepted : 14 July 2000 / Published : 26 July 2000Abstract: Several perinaphthenone/phenylphenalenone compounds were synthesized to es-tablish a relationship between structure and antifungal activity against Mycosphaerella fijie n-sis. Substitutions on the unsaturated carbonyl system or addition of a phenyl group reducedantibiotic activity.Keywords: phenylphenalenones, synthesis, antifungal activity, Mycosphaerella fijiensis .IntroductionPhytoalexins are natural antibiotic compounds proposed as fungicides or templates for production ofnew pesticides [1]. Recently, the search for novel antifungal compounds has received special attentionas a result of an enhanced microbial resistance to current pesticides.Banana plants are affected by the pathogenic fungi Fusarium oxysporum var. cubensis type 4 andMycosphaerella fijiensis , causal agents of the diseases named Black Sigatoka and Panama Disease, r e-spectively. These diseases can drastically reduce banana production by as much as ca. 20% [2]. Undercolonization by these microorganisms or treatment of the leaves with kanamycin, banana plants producetwo types of phytoalexins, 9-phenylphenalenones (also known as musanolones [3]) and 4-phenylphenalenones [4], The main aim of the present work was to synthesize several structurally-relatedcompounds and to determine the relationship between phytoalexin structure and their antifungal effectsagainst M. fijiensis .Results and DiscussionThe planned synthetic approach involved a 1,4-addition of a Grignard reagent to a perinaphthenone,followed by reduction with DDQ, epoxidation with

Effects of diterpenes from latex of Euphorbia lactea and Euphorbia laurifolia on human immunodeficiency virus type 1 reactivation

The persistence of latent HIV-infected cellular reservoirs represents the major hurdle to virus eradication in patients treated with highly active antiretroviral therapy, referred to as HAART. HIV-1 reservoirs are long-lived resting CD4+ memory cells containing the virus latently integrated. Since the HIV-1 reservoirs are not targeted by HAART, reactivation therapy has been suggested to purge viral latency. Bioassay-guided study of an ethyl acetate extract of Euphorbia laurifolia afforded two isomeric diterpenes that showed differential activity over HIV-1 reactivation. A previously reported compound was isolated too from Euphorbia lactea. This compound showed a potent HIV-1 reactivating effect. Bioassays results showed that HIV-1 reactivation activity is influenced by distinct structural characteristics.

Leishmanicidal activity of aliphatic and aromatic lactones: correlation structure-activity.

Several aliphatic and aromatic lactones and two dimers were synthesized using the sequence: allylation - esterification - metathesis. These compounds were active in vitro against intracellular amastigotes of Leishmania panamensis. The structure-activity relationship showed the importance of the aliphatic side chain to enhance the biological activity and to obtain lower cytotoxicity. It was also observed that a decrease in the size of the lactone ring increases the selectivity index.

Isomeric oxabenzochrysenones from Musa acuminata and Wachendorfia thyrsiflora

Two new oxabenzochrysenones (naphthoxanthenones), representing phenylphenalenone-related natural products, were isolated from Musa acuminata and Wachendorfia thyrsiflora .

In vivo Antimalarial Activity of α-Mangostin and the New Xanthone δ-Mangostin

Based on the previously reported in vitro antiplasmodial activity of several xanthones from Garcinia mangostana, two xanthones, α‐mangostin and a new compound, δ‐mangostin, were isolated from mangosteen husk, and the in vitro antiplasmodial and cytotoxic effects were determined. α‐Mangostin was more active against the resistant Plasmodium falciparum chloroquine‐resistant (FCR3) strain (IC50 = 0.2 ± 0.01 μM) than δ‐mangostin (IC50 = 121.2 ± 1.0 μM). Furthermore, the therapeutic response according to the administration route was evaluated in a Plasmodium berghei malarial murine model. The greatest therapeutic response was obtained with intraperitoneal administration; these xanthones reduced parasitemia by approximately 80% with a daily dose of 100 mg/kg administered twice a day for 7 days of treatment. Neither compound was effective by oral administration. Noticeable toxicological effects were not observed. In addition to the antimalarial effect of these xanthones isolated from G. mangostana husk, the availability of larger amounts of husk raw material to purify the bioactive xanthones is advantageous, permitting additional preclinical assays or chemical transformations to enhance the biological activity of these substances. Copyright

Effect of Salicylic Acid and Structurally Related Compounds in the Accumulation of Phytoalexins in Cotyledons of Common Bean (Phaseolus vulgaris L.) Cultivars

In the present work, isoflavonoid phytoalexin production in response to the application of salicylic acid in cotyledons of four common bean (Phaseolus vulgaris) cultivars (SA) was evaluated. The time-course and dose-response profiles of the induction process were established by quantifying the isoflavonoids by HPLC. Cotyledons of anthracnose-resistant cultivars induced by SA produced substantially higher phytoalexin contents as compared to the susceptible ones. In addition, maximum levels of phytoalexins (50–100 fold increases) were reached between 96 and 144 h, and when a concentration of SA from 3.62 to 14.50 mM was used. The observations also indicate that there was a relatively good correlation between the phytoalexin contents and the inhibitory effect against C. lindemuthianum; the higher antifungal activity was observed during the first 48 hours for extracts from cotyledons treated with SA at 1.45 and 3.62 mM, and between 96 and 144 h after induction. Finally, compounds structurally related to SA (dihydro-quinazolinones and some imines) showed a strong elicitor effect. Moreover, induced extracts from cotyledons treated with these potential elicitors, besides the properly elicitors, displayed a weak to moderated antifungal activity. These compounds may be considered good candidates for developing of new phytoprotectants. Furthermore, phytoalexin-eliciting substances may contribute for selecting disease resistant cultivars.