Orlando Muñoz

Ethylene production and peroxidase activity in aphid-infested barley.

The purpose of this work was to investigate whether ethylene is involved in the oxidative and defensive responses of barley to the aphids Schizaphis graminum (biotype C) and Rhopalophum padi. The effect of aphid infestation on ethylene production was measured in two barley cultivars (Frontera and Aramir) that differ in their susceptibility to aphids. Ethylene evolution was higher in plants infested for 16 hr than in plants infested for 4 hr in both cultivars. Under aphid infestation, the production of ethylene was higher in cv. Frontera than in Aramir, the more aphid susceptible cultivar. Ethylene production also increases with the degree of infestation. Maximum ethylene evolution was detected after 16 hr when plants were infested with 10 or more aphids. Comparing the two species of aphids, Schizaphis graminum induced more ethylene evolution than Rhopalosiphum padi. Infestation with S. graminum increased hydrogen peroxide content and total soluble peroxidase activity in cv. Frontera, with a maximum level of H2O2 observed after 20 min of infestation and the maximum in soluble peroxidase activity after 30 min of infestation. When noninfested barley seedlings from cv. Frontera were exposed to ethylene, an increase in hydrogen peroxide and in total peroxidase activity was detected at levels similar to those of infested plants from cv. Frontera. When noninfested plants were treated with 40 ppm of ethylene, the maximum levels of H2O2 and soluble peroxidase activity were at 10 and 40 min, respectively. Ethylene also increased the activity of both cell-wall-bound peroxidases types (ionically and covalently bound), comparable with infestation. These results suggest that ethylene is involved in the oxidative responses of barley plants induced by infestation.

Tropane alkaloids from Schizanthus litoralis

Abstract Six new tropane alkaloids have been isolated from the leaves of the endemic Chilian plant Schizanthus litoralis (Solanaceae). The new structures include a new tropanol dimer of itaconic acid together with 6β-senecioyloxytropan-3α-methylmesaconate, 6β-cinnamoyloxytropan-3α-methylmesaconate, 6β-senecioyloxytropan-3α-ol and cis-trans N-(4-hydroxyphenethyl) ferulamides. Other known alkaloids were also isolated. Their structures were elucidated by spectroscopic methods.

Changes in ferulic acid and lipid content in aphid-infested barley

Abstract Aphid infestation reduced the susceptibility of barley cultivars to new infestations. The intrinsic growth rate of aphids was lower in the populations reared on previously infested plants, than in populations reared on barley without previous infestation. Changes in the content of ferulic acid, and other aromatic compounds and lipids, were detected in barley seedlings infested by the aphid, Schizaphis graminum . Ferulic acid concentration increased from 4 to 14 μ mol kg − 1 fresh wt, as a function of infestation level by aphids. Survival of aphids reared with diets containing this compound was lower than the controls. Aphid survival at 24 hours was under 58% and 40% in diets with 10 and 20 μM ferulic acid, respectively. In diets without the compound, survival was 84%. Analysis of alicyclic and aliphatic compounds in extracts of infested and non-infested barley plants showed differences in the relative concentrations of compounds. Our results suggest that the increase of ferulic acid induced by initial infestation may protect the plant against new infestations. Changes in lipid concentrations could be an acclimatization response of the plant to water-stress caused by the aphids.

Absolute configuration determination and conformational analysis of (−)‐(3S,6S)‐3α,6β‐diacetoxytropane using vibrational circular dichroism and DFT techniques

The absolute configuration of semisynthetic (-)-3alpha,6beta-acetoxytropane 1, prepared from (-)-6beta-hydroxyhyoscyamine 2, has been determined using vibrational circular dichroism (VCD) spectroscopy. The vibrational spectra (IR and VCD) were calculated using DFT at the B3LYP/DGDZVP level of theory for the eight more stable conformers which account for 99.97% of the total relative abundance in the first 10 kcal/mol range. The calculated VCD spectra of all considered conformations showed two distinctive spectral ranges, one between 1300 and 1200 cm(-1), and the other one in the 1150-950 cm(-1) region. When compared with the experimental VCD spectrum, the first spectral region confirmed the calculated conformational preferences, whereas the second region showed little change with conformation, thus allowing the determination of the absolute configuration of 1 as (3S,6S)-3alpha,6beta-diacetoxytropane. Also, the bands in the second region showed similarities between 1 and 2 in both the experimental and calculated VCD spectra, suggesting that these bands are mainly related to the absolute configuration of the rigid tropane ring system, since they show conformational independency, no variations with the nature of the substituent, and are composed by closely related vibrational modes.

The isolation and structure determination of chilenone A, a putative dimer of 2-methyl-3(2H)-furanone from the marine alga

Abstract The isolation of chilenone A from Laurencia chilensis and the determination of its structure by spectral and x-ray crystallographic techniques is described.

Contenido de flavonoides y compuestos fenólicos de mieles chilenas e índice antioxidante

A comparison of the phenolic content of several Chilean honeys showed great variations in flavonoid concentration among the samples analysed. Higher amounts of phenolics are found in honey from dry climates. The antioxidant effect of extracts, using ORAC analysis, did not correlate with the flavonoid content or with the total phenolic concentration.

Tropane alkaloids from Schizanthus grahamii

Abstract Three new tropanol dimers of mesaconic and itaconic acids and 3α-senecioyloxytropane, together with other known alkaloids, were isolated from Schizanthus grahamii . The structures of the new compounds were established by spectroscopic and chemical transformations including 2-D long-range 13 C- 1 H correlations.

Chemical study and anti-inflammatory, analgesic and antioxidant activities of the leaves of Aristotelia chilensis (Mol.) Stuntz, Elaeocarpaceae

Objectives  Aristotelia chilensis leaves (Elaeocarpaceae) are used in Chilean folk medicine to treat pain and inflammation. A bioguided study was carried out on serial extracts (hexane, dichloromethane, methanol, aqueous extract (INFU) and a crude mixture of alkaloids (ALK‐MIX). All extracts were evaluated for (1) topical administration against both arachidonic acid and 12‐deoxyphorbol‐13‐decanoate (TPA)‐induced inflammation in mice and (2) per‐os administration against inflammation by λ‐carrageenan‐induced paw oedema in guinea‐pigs and (3) topical analgesia in tail flick and formalin models and per‐os writhing test in mice.

Phenolic compounds of propolis from Central Chilean matorral.

Abstract Pinocembrin, acacetin, galanguin, izalpin, kaempferide, prenyletin and diarytheptane were isolated from propolis from Central Chile.

A new sesquiterpene from Maytenus boaria (Celastraceae); crystal structure and absolute configuration

Abstract Hitherto all the agarofuran sesquiterpenes substituted at C-4 isolated from the Celastraceae had a 4S configuration but now a sesquiterpene diol with a 4R configuration has been isolated and studied by x ray diffraction analysis and application of the Horeau method.