Raffaele Tabacchi

Resistance factors to grey mould in grape berries: identification of some phenolics inhibitors of Botrytis cinerea stilbene oxidase

Abstract Grey mould caused by Botrytis cinerea is one of the most important diseases of grapes. Between bloom and veraison, grape berries are resistant to B. cinerea, although they can harbour the pathogen without any visible signs of disease development. After veraison, B. cinerea can produce disease in susceptible grape varieties (e.g. Gamay), but remains quiescent in resistant varieties (e.g. Gamaret). Pathogen resistance in the quiescent stage is not yet fully understood, but is thought to involve multiple parameters including chemical and mechanical factors. The pathogenesis of B. cinerea is essentially linked to excretion of lytic enzymes such as polyphenoloxidases or laccases. One lytic enzyme, stilbene oxidase, can detoxify grape stilbenic phytoalexins, destroying the grapes’ defence mechanisms and allowing the fungus to grow. Some constitutive grape berry phenolic compounds, however, strongly inhibit stilbene oxidase activity. Constitutive berry phenolic compounds were isolated from Gamay and Gamaret varieties and their biological activities, concentrations and chemical structures were comparatively analysed. Catechin, epicatechin-3-O-gallate, trans-caftaric, trans- and cis-coutaric and trans-coumaric acids, taxifoline-3-O-rhamnoside and quercetine-3-O-glucuronide were identified as potent stilbene oxidase inhibitors. High concentrations of some of those compounds could be closely involved in the persistence of the quiescent stage of B. cinerea, between bloom and veraison in all grape varieties and after veraison in resistant varieties.

Eutypine, a phytotoxin produced by Eutypa lata the causal agent of dying-arm disease of grapevine

Abstract A phytotoxic metabolite has been isolated from liquid cultures of Eutypa lata and structurally characterized as 4-hydroxy-3-(3-methylbut-3-en-1-ynyl)benzaldehyde, named eutypine. It was detected by GC-MS and MS-MS analyses in the crude sap and the inflorescences of diseased plants and was not present in healthy material.

The Synthesis of Natural Acetylenic Compounds from Stereum hirsutum

The regioselective synthesis of two new acetylenic compounds, sterehirsutinal (1) and sterehirsutinol (2), isolated recently from culture medium of the fungus Stereum hirsutum, is reported.

Acetylenic aromatic compounds from Stereum hirsutum

Stereum hirsutum is a one of several fungi involved in a grapevine disease called esca. From the culture medium of this fungus, four new acetylenic compounds 1-3 and 6 have been isolated and identified. Structural elucidation and biological activity are reported.

Two volatile β-chromenes fromWisteria sinensis flowers

Abstract Among the character-donating components of the fragrance of Wisteria sinensis flowers, two new β-chromenes were detected by GC-MS and GC-FTIR of

Gas Chromatographic Enantiomer Separation of Atropisomeric PCBs Using Modified Cyclodextrins as Chiral Phases

Gas chromatography (GC) has been utilized for the study of enantiomer resolution of the atropisomers of PCBs, o,p´-DDD and o,p´-DDT. Different substituents and concentrations of cyclodextrin, capillary dimensions and type of stationary phase films have been investigated to achieve the resolution of as many of the atropisomers on one column as possible. The results indicated that the butyl substitution of 6-hydroxyl and the methyl substitution of 2- and 3-hydroxyl were the most promising for the enantiomeric separation. Using Capillary Electrophoresis (CE), the trimers and monomers of PM-β-CDs were compared for enantiomeric resolution, as well as comparing the cationic PMMA-β-CD with the anionic HS-β-CD. In these studies the trimer did not show an improved resolution for mepivacaine, when compared to the equimolar concentration of the monomer. The cationic CD gave increased resolution values for ibuprofen when compared to the anionic CD. A scheme for reversing enantiomeric elution order of both the basic propranolol and acidic ibuprofen is also presented, with the aim of facilitating the detection of impurities in a high sample loading. The detection of 1% of each enantiomer of propranolol, and 1% of R(-)-ibuprofen, was demonstrated, with elution prior to the tailing peak of the corresponding enantiomer. Dimethylacrylamide-coated capillaries were used in this work, and the stability of this coating was demonstrated, giving a highly reduced electroosmotic flow for up to six months. Enantiomeric baseline separations of omeprazole and 5-hydroxyomeprazole have also been achieved with both CE and Open Tubular Capillary Electrochromatography (OT-CEC) methods. With CE-UV, both a non-aqueous method (using HDMS-β-CD) and an aqueous method (using HS-β-CD) were used for enantiomeric resolution of the two racemates. Resolution of omeprazole was also achieved using CE-Electrospray Ionization-Mass Spectrometry (ESI-MS). In OT-CEC, avidin was immobilized on the inside surface of a fused silica capillary and was employed as chiral selector for the enantiomeric baseline resolution of omeprazole and 5-hydroxyomeprazole.

Relationship between the fungus Ceratocystis fimbriata coffea and the canker disease of the coffee tree

Abstract The active fraction of an extract of the fungus Ceratocystis fimbriata coffea , which is responsible for the canker disease of the coffee tree, provided 13 metabolites which come mainly from the polyketide pathway. In addition to the five isocoumarins previously described, eight further metabolites are reported. Some of the isolated compounds showed necrotic symptoms on the coffee tree at concentrations of ca 1–4 × 10 −3 M. Previously unpublished spectroscopic data of some of the isolated compounds are reported.

Semi-preparative gas chromatographic separation of all-trans-perhydrotriphenylene enantiomers on a chiral cyclodextrin stationary phase

Enantiomers of all-trans-perhydrotriphenylene (PHTP) were separated by gas chromatography using heptakis(6-O-tert.-butyldimethylsilyl-2,3-di-O-methyl)-beta-cyclodextrin (TBDMS-beta-CD) as the chiral selector. Conditions for semi-preparative separations were established using a 2 m x 2 mm I.D. packed column and subsequently extended to a 1.8 m x 4 mm I.D. column which enabled separations on a mg scale. The column packing was TBDMS-beta-CD dissolved in SE-54 coated on Chromosorb P AW-DMCS 80-100 mesh. Optimization of the chromatographic conditions (oven temperature, carrier gas flow, and column load) with respect to better efficiency and peak retention resulted in a system capable of separating up to 10 mg of the racemate per day. Purities of separated enantiomers were determined by capillary gas chromatography. Yields and purities of the fractions obtained by single- and double-step separations are compared. Highly enriched enantiomers with purities of up to 99.6% (99.2% ee) were obtained by a single separation step.

Qualitative Analysis of Grapevine Tannins by Mass Spectrometry and their Inhibitory Effect on Stilbene Oxidase of Botrytis cinerea

The pure tannin extracts from grape berries of Gamay and Gamaret varieties contain a mixture of proanthocyanidins and proanthocyanidin gallates. A sensitive LC-MS method has been developed for the qualitative analysis of the oligomers and polymeric fractions. The potential of ESI-IT or MALDI-TOF mass spectrometry permit us to characterize these tannins. Polymers were fractionated according to the mean degree of polymerization (mDP), using either a divinylbenzene phase or a glass powder. The mDP is obtained by thiolysis reaction and the fractions are analyzed by MS. Polymeric proanthocyanidins (PPRA) were purified from grape berries at full bloom, pea size, bunch closure, veraison and harvest, their mDP calculated and their inhibitory capacity on B. cinerea stilbene oxidase tested at 3.5 to 70 nmoles for 3 ml of enzymatic reaction volume. ED50 of PPRA concentrations was measured for each developmental stage and for both grape varieties Gamay (sensitive to grey mould) and Gamaret (resistant). The higher the mDP of PPRA fraction, the more effective is the inhibitory activity. From grape berry pea size, mDP of PPRA of Gamaret (9.53 to 11.77) were always higher than those of Gamay (7.46 to 8.74) and ED50 of Gamaret PPrA were under 5 nmoles 3ml - 1 while ED50 of Gamay PPRA were at 6.5 to 7.25 nmoles 3 ml - 1 .

Thermal Decomposition of Lichen Depsides

The thermal decomposition of the following lichen depsides has been described: lecanoric acid, gyrophoric acid, evernic acid, perlatolic acid, planaic acid, confluentic acid, atranorin, 4-O-de-methylbarbatic acid, and sekikaic acid. Main reaction products are decarboxylated compounds, phenolic units, rearranged depsides, and xanthones. Triethylammonium salts of depside carboxylic acids decompose at reasonably lower temperature than the corresponding free acids.