Ali Haidour

MECHANISMS FOR SOLVENT TOLERANCE IN BACTERIA

The development of tolerance in Pseudomonas putida DOT-T1 to toluene and related highly toxic compounds involves short- and long-term responses. The short-term response is based on an increase in the rigidity of the cell membrane by rapid transformation of the fatty acid cis-9,10-methylene hexadecanoic acid (C17:cyclopropane) to unsaturated 9-cis-hexadecenoic acid (C16:1,9 cis) and subsequent transformation to the trans isomer. The long-term response involves in addition to the changes in fatty acids, alterations in the level of the phospholipid polar head groups: cardiolipin increases and phosphatidylethanolamine decreases. The two alterations lead to increased cell membrane rigidity and should be regarded as physical mechanisms that prevent solvent penetrance. Biochemical mechanisms that decrease the concentration of toluene in the cell membrane also take place and involve: (i) a solvent exclusion system and (ii) metabolic removal of toluene via oxidation. Mutants unable to carry out cis → trans isomerization of unsaturated lipids, that exhibit altered cell envelopes because of the lack of the OprL protein, or that are unable to exclude toluene from cell membranes are hypersensitive to toluene.

Terpenoids and sterols from the wood of Abies pinsapo

Abstract From the neutral fraction of the hexane extract of the wood of Abies pinsapo 11 sesquiterpenoids, seven diterpenoids, three triterpenoids and two sterols have been identified. Three of them are new natural products: 3β-hydroxy-13-epimanool, (23 R ,25 R )-3α-methoxy-9,19-cyclo-9β-lanostan-26,23-olide and (22 S )-5α-ergostane-3α,22-diol. Their structures were established by spectroscopic methods and chemical correlations.

Diterpenoids and cyclolanostanolides from Abies marocana

Abstract From the neutral fraction of a hexane extract of the leaves of Abies marocana, eight sesquiterpene hydrocarbons, 10 diterpenoids, and two triterpenoids have been identified. Seven are new natural products: labda-7,12Z,14-triene, labda-8(17),12Z,14-triene, labda-7,11E,13Z-triene and labda-8(17),11E,13Z-triene, 7α,18-dihydroxyabieta-8,11,13-triene, (23R)-3α-hydroxy-9,19-cyclo-9β-lanostan-26,23-olide and (23R)-3α-hydroxy-9,19-cyclo-9β-lanost-24-en-26,23-olide. Their structures have been established by spectroscopic methods and chemical correlations.

Endoperoxide diterpenoids and other constituents from Abies marocana

Abstract From the acid fraction of the hexane extract of the needles of Abies marocana three endoperoxide diterpenoids, methyl 12α-hydroxyabietate and a triterpenoid, in addition to other resin acids have been isolated.

General Access to Taiwaniaquinoids Based on a Hypothetical Abietane C7–C8 Cleavage Biogenetic Pathway

A new strategy for synthesizing taiwaniaquinoids, a group of terpenoids with an unusual rearranged 5(6→7) or 6-nor-5(6→7)abeo-abietane skeleton, which exhibit promising biological activities, is reported. The procedure, based on the cleavage of the C7-C8 double bond of abietane diterpenes, is the only one yet reported for synthesizing C(20) taiwaniaquinoids bearing a carbon function on the cyclopentane B ring; it is also applicable to the synthesis of the wide variety of existing taiwaniaquinoids. Utilizing this, (-)-taiwaniaquinone A, F, G, and H, (-)-taiwaniaquinol B, and (-)-dichroanone have been synthesized from (+)-abietic acid. The versatility of this strategy allows us to propose the abietane C7-C8 cleavage as a possible biosynthetic pathway to this type of rearranged diterpenes; this proposal seems to be supported by phytochemical evidence.

Polyacetylenes, terpenoids and flavonoids from Bupleurum spinosum

Abstract From the aerial parts of Bupleurum spinosum , four new natural products have been isolated: (3 E ,5 Z ,7 Z ,9 E )-trideca-3,5,7,9-tetraene,10(14)-trien-1-ol, Z -8-decene-4,6-diyn-1-ol, ( E , E )-pentadeca-5,7-diene-9,11,13-triyn-2-one,tamarixetin 3-robinobioside. A series of esters of achilleol A with fatty acids has been also found.

Terpenoids of the wood of Abies marocana

We have characterized seven sesquiterpen- oids, five triterpenoids, four of them juvenile hormone analogues, 14 diterpenoids, five triterpenoids and two sterols, besides a number of fatty acids. Compounds 2, 5, 6 and g are new natural products, and 3 and 4 are described for the first time in the genus

Two sesquilignans from the wood of Abies marocana

Abstract From the chloroform extract of the wood of Abies marocana , consisting mainly of lignans, the acetoxyl derivatives of the new sesquilignans, 4,4″,7″,9,9″-pentahydroxy-3,3′,3″-trimethoxy-4′,8″:7,9′-bis-epoxy-8,8′-sesquineolignan and 4,4″,7″,9,9′,9″-hexahydroxy-3,3′,3″-trimethoxy-4′,8″-epoxy-8,8′-sesquineolignan were isolated; the trivial names, sesquimarocanols A and B, were subsequently assigned, respectively. Also, (9′ R )-9′-hydroxylariciresinol tetraacetate, (7′ R )-7′-hydroxylariciresinol tetraacetate and sesquipinsapol B pentaacetate, which had previously only been found in A. pinsapo , were isolated, together with some well known compounds. The new structures were established by spectroscopic methods. Certain cytotoxic activity assays were performed on the new compounds.

Potential of Toluene-Degrading Systems for the Construction of Hybrid Pathways for Nitrotoluene Metabolism

Wastes from manufacturing processes, together with the widespread use of some nitroaromatic compounds, have polluted waters and soils. Because of their toxicity and mutagenicity, some of these compounds have been designated pollutants whose elimination is a high priority (25). A variety of alternative treatments including physical, chemical and biological (21), have been developed to reduce or eliminate contamination due to hazardous nitroorganic compounds. Physical treatments comprise absorption to activated carbon, filtration and incineration. Chemical approaches involve solvent extraction or surfactant precipitation. These treatments are expensive, and may in some cases generate unwanted products (22). The biological approach, including continuous and batch treatments of liquid wastes, and composting and soil treatments, is usually cheaper and involves less risk to human health or the environment (12, 23, 54). However, nitroaromatic compounds are relatively refractory to mineralization by microbes.

Two glutaric acid derivatives from olives

Abstract Two linear compounds were isolated from the ethyl acetate extract of residues resulting from olive oil processing. These compounds were characterized by NMR and identified as 3-[1-(hydroxymethyl)-(E)1-propenyl] glutaric acid and 3-[1-(formyl)-(E)1-propenyl] glutaric acid. Spectra of the products resulting from reduction and saponification confirmed the proposed structures. These products are structural components of a more complex molecule, oleuropein, which confers a bitter taste to olives.