Search

This analytical method is a validated measurement procedure for the determination of diphenylether [101-84-8] in workplace air in a concentration range of one tenth up to twice the currently valid Occupational Exposure Limit Value (OELV) in Germany of 7.1 mg/m3. For sampling a defined volume of air is drawn through a binder-free quartz fiber filter followed by a silica gel sorbent tube. The flow rate is set to 0.5 l/min and sampling duration is 2 hours (which correspond to a sampling volume of 60 l). Diphenylether is extracted with 2-propanol and subsequently analysed using liquid chromatography with diode array detection. The quantitative determination is based on a calibration function. The limit of quantification is 0.008 mg/m3 based on an air sample volume of 60 l. The mean recovery is 95.3% and the expanded uncertainty for the validation range of 0.71 to 14.2 mg/m3 is 24 to 25%.

Ochraceopetalin (1), a mixed-biogenetic salt compound and its component 2 were isolated from the culture broths of a marine-derived fungus, Aspergillus ochraceopetaliformis. Based on combined spectroscopic and chemical analyses, the structure of 1 was determined to be a sulfonated diphenylether-aminol-amino acid ester guanidinium salt of an unprecedented structural class, while 2 was determined to be the corresponding sulfonated diphenylether. Ochraceopetaguanidine (3), the other guanidine-bearing aminol amino acid ester component, was also prepared and structurally elucidated. Compound 1 exhibited significant cytotoxicity against K562 and A549 cells.

Ochraceopetalin (1), a mixed-biogenetic salt compound and its component 2 were isolated from the culture broths of a marine-derived fungus, Aspergillus ochraceopetaliformis. Based on combined spectroscopic and chemical analyses, the structure of 1 was determined to be a sulfonated diphenylether-aminol-amino acid ester guanidinium salt of an unprecedented structural class, while 2 was determined to be the corresponding sulfonated diphenylether. Ochraceopetaguanidine (3), the other guanidine-bearing aminol amino acid ester component, was also prepared and structurally elucidated. Compound 1 exhibited significant cytotoxicity against K562 and A549 cells.

The nonylphenol-degrading bacterium Sphingomonas sp. strain NP5 has a very unique monooxygenase that can attack a wide range of 4-alkylphenols with a branched side chain. Due to the structural similarity, it can also attack bisphenolic compounds, which are very important materials for the synthesis of plastics and resins, but many of them are known to or suspected to have endocrine disrupting effects to fish and animals. In this study, to clarify the substrate specificity of the enzyme (NmoA) for bisphenolic compounds, degradation tests using the cell suspension of Pseudomonas putida harboring the nonylphenol monooxygenase gene (nmoA) were conducted. The cell suspension degraded several bisphenols including bisphenol F, bisphenol S, 4,4&prime, dihydroxybenzophenone, 4,4&prime, dihydroxydiphenylether, and 4,4&prime, thiodiphenol, indicating that this monooxygenase has a broad substrate specificity for compounds with a bisphenolic structure.

A continuous arms race between the development of novel antibiotics and the evolution of corresponding resistance mechanisms in bacteria has been observed, since antibiotic agents like arsphenamines (e.g. Salvarsan, developed by Paul Ehrlich [1]), sulphonamides (e.g. Prontosil, Gerhard Domagk [2]) and penicillin (Alexander Fleming [3]) were first applied to effectively cure bacterial infections in the early 20th century. The rapid emergence of resistances in contrast to the currently lagging discovery of antibiotics displays a severe threat to human health. Some serious infectious diseases, such as tuberculosis or melioidosis, which were either thought to be an issue only in Third-World countries in case of tuberculosis, or regionally restricted with respect to melioidosis, are now on the rise to expand to other areas. In contrast, methicillin-resistant Staphylococcus aureus (MRSA) is already present in clinical setups all over the world and causes severe infections in immunocompromised patients. Thus, there is an urgent need for new and effective antimicrobial agents, which impair vital functions of the pathogen’s metabolism. One central metabolic pathway is represented by the bacterial fatty-acid synthesis pathway (FAS II), which is essential for the synthesis of long and branched-chain fatty acids, as well as mycolic acids. These substances play a major role as modulating components of the properties of the most important protective barrier – the cell envelope. The integrity of the bacterial cell wall and the associated membrane(s) is crucial for cell growth and for protection against physical strain, intrusion of antibiotic agents and regulation of uptake of ions and other small molecules. Thus, this central pathway represents a promising target for antibiotic action against pathogens to combat infectious diseases. The last and rate-limiting step is catalysed by the trans-2-enoyl-ACP reductase (ENR) FabI or InhA (in mycobacteria), which has been demonstrated to be a valuable target for drug design and can be addressed, amongst others, by diphenyl ether (DPE) compounds, derived from triclosan (TCL) – the first one of this class which was discovered to bind to ENR enzymes [4, 5]. Based on this scaffold, inhibitors containing different combinations of substituents at crucial positions, as well as a novel type of substituent at position five were investigated regarding their binding behaviour towards the Burkholderia pseudomallei and Mycobacterium tuberculosis ENR enzymes bpFabI and InhA, respectively, by structural, kinetic and in-vivo experiments. Generally, substitution patterns modulate the association and dissociation velocities of the different ENR inhibitors in the context of the two-step slow-onset binding mechanism, which is observed for both enzymes. These alterations in the rapidity of complex formation and decomposition have a crucial impact on the residence time of a compound and hence, on the pharmacokinetic properties of potential drug candidates. For example, the substituents at the 2’-position of the DPE scaffold influence the ground- and transition state stability during the binding process to bpFabI, whereas 4’-substituents primarily alter the transition state [6]. The novel triazole group attached to the 5-position of the scaffold, targeting the hydrophobic part of the substrate-binding pocket in InhA, significantly enhances the energy barrier of the transition state of inhibitor binding [7] and decelerates the association- as well as the dissociation processes. Combinations with different substituents at the 2’-position can enhance or diminish this effect, e.g. by ground-state stabilisation, which will result in an increased residence time of the respective inhibitor on InhA. Further structural investigations carried out in this work, confirm the proposed binding mode of a customised saFabI inhibitor [8], carrying a pyridone moiety on the DPE scaffold to expand interactions with the protein environment. Structural and preliminary kinetic data confirm the binding of the same inhibitor to InhA in a related fashion. Comparisons with structures of the ENR inhibitor AFN-1252 [9] bound to ENR enzymes from other organisms, addressing a similar region as the pyridone-moiety of the DPE inhibitor, suggest that also the DPE inhibitor bears the potential to display binding to homologues of saFabI and InhA and may be optimised accordingly. Both of the newly investigated substituents, the pyridone moiety at the 4’-position as well as the 5-triazole substituent, provide a good starting point to modify the DPE scaffold also towards improved kinetic properties against ENR enzymes other than the herein studied and combining both groups on the DPE scaffold may have beneficial effects. The understanding of the underlying binding mechanism is a crucial factor to promote the dedicated design of inhibitors with superior pharmacokinetic characteristics. A second target for a structure-based drug-design approach is the interaction surface between ENR enzymes and the acyl-carrier protein (ACP), which delivers the growing acyl chain to each distinct enzyme of the dissociated FAS-II system and presumably recognises its respective interaction partner via electrostatic contacts. The interface between saACP and saFabI was investigated using different approaches including crosslinking experiments and the design of fusion constructs connecting the ACP and the FabI subunits via a flexible linker region of varying lengths and compositions. The crosslinking studies confirmed a set of residues to be part of the contact interface of a previously proposed complex model [10] and displayed high crosslinking efficiency of saACP to saFabI when mutated to cysteine residues. However, crystals of the complex obtained from either the single components, or of the fusion constructs usually displayed weak diffraction, which supports the assumption that complex formation is highly transient. To obtain ordered crystals for structural characterisation of the complex it is necessary to trap the complex in a fixed state, e.g. by a high-affinity substrate attached to ACP [11], which abolishes rapid complex dissociation. For this purpose, acyl-coupled long-residence time inhibitors might be a valuable tool to elucidate the detailed architecture of the ACP-FabI interface. This may provide a novel basis for the development of inhibitors that specifically target the FAS-II biosynthesis pathway., Seit Beginn der Anwendung antibiotischer Substanzen wie Arsphenaminen, z.B. Salvarsan, entwickelt von Paul Ehrlich [1], Sulfonamiden, z.B. Prontosil, dessen antibakterielle Wirksamkeit durch Gerhard Domagk nachgewiesen wurde [2], oder des von Alexander Fleming entdeckten Penicillins [3] zur effektiven Bekämpfung von Infektionskrankheiten Anfang des 20. Jahrhunderts findet ein kontinuierliches Wettrüsten zwischen der Entstehung von Antibiotikaresistenzen in Bakterien und der Entwicklung neuer Antibiotika statt. Vor allem die zügige Entstehung von Resistenzen im Gegensatz zum eher stockenden Fortschritt der Entdeckung neuer Antibiotika stellt ein ernstzunehmendes Risiko für die menschliche Gesundheit dar. Einige stark lebensbedrohliche Infektionskrankheiten, darunter Tuberkulose und Melioidose, erfahren dadurch eine erhöhte Verbreitung. Ein Anstieg der Zahl der Tuberkuloseerkrankungen in Gebieten, in denen die Krankheit bereits als ausgerottet galt, beispielsweise in Europa; oder im Falle der Melioidose, eine Verbreitung in Gebiete, in denen die Krankheitserreger natürlicherweise nicht vorkommen; sind u.a. die Folgen fehlender Wirkstoffe zur Bekämpfung resistenter Stämme. Methicillinresistente Staphylococcus-aureus- (MRSA-) Stämme sind hingegen bereits fast weltweit in Krankenhäusern verbreitet und gelten dort als Quelle schwerer Infektionen, die vor allem für Patienten mit geschwächtem Immunsystem eine ernsthafte Bedrohung darstellen. Die mannigfaltigen Vorkommen resistenter Erreger und die eingeschränkten Behandlungsmöglichkeiten dadurch verursachter Infektionen machen die Entwicklung neuer, wirksamer Antibiotika dringend notwendig. Ein zentraler Stoffwechselweg der Bakterien ist die Fettsäurebiosynthese II, die im Hinblick auf die Herstellung lang- und verzweigtkettiger Fettsäuren sowie von Mykolsäuren essentiell ist. Die Zusammensetzung der Fettsäuren trägt maßgeblich zur Funktionsfähigkeit der unentbehrlichen Schutzbarriere der Zelle – nämlich der Zellhülle – bei. Eine intakte Zellwand und deren assoziierte Membranen schützen die Zelle vor physikalischem Stress, vor dem Eindringen antibiotischer Substanzen und regulieren die Aufnahme anderer Kleinmoleküle und Ionen. Genau aus diesem Grunde stellt die Fettsäurebiosynthese ein attraktives Ziel für die Entwicklung von Antibiotika dar. Die Enoyl-ACP-Reduktase (ENR), welche den letzten und geschwindigkeitsbestimmenden Schritt des Synthesezyklus katalysiert, wurde als hervorragendes Zielmolekül identifiziert und wird unter anderem von Diphenylethern gehemmt. Diese Verbindungen sind von Triclosan abgeleitet, dessen Bindung an ENR-Enzyme als erstem Vertreter dieser Stoffklasse nachgewiesen werden konnte [4, 5]. Basierend auf dem Diphenylethergrundgerüst von Triclosan wurden Inhibitoren mit unterschiedlichen Substitutionsmustern bezüglich ihrer Bindungseigenschaften an die ENR-Enzyme von Burkholderia pseudomallei (bpFabI) und Mycobacterium tuberculosis (InhA) untersucht. Kritische Positionen dieses Grundgerüstes wurden mit verschiedenen, chemischen Gruppen versehen und die Bindung an diese beiden Enzyme anschließend strukturell, kinetisch und am lebenden Organismus charakterisiert. In beiden Fällen üben die Substitutionsmuster einen beträchtlichen Einfluss auf die Assoziations- und Dissoziationsgeschwindigkeiten der verschiedenen Inhibitoren im Rahmen des verlangsamten Zweischrittassoziationsmechanismus aus, welche wiederum die Verweildauer des Inhibitors am Enzym und dessen pharmakokinetische Eigenschaften bestimmen. Die Beschaffenheit der 2‘-Substituenten beeinflusst beispielsweise die Stabilität des Grund- sowie des Übergangszustandes im Bindungsgeschehen an bpFabI, wohingegen 4‘-Substituenten hauptsächlich zu Stabilitätsänderungen im Übergangszustand beitragen [6]. Die Einführung des Triazolsubstituenten an der 5-Position des Diphenylethergerüsts führt zu einer signifikanten Erhöhung der Energiebarriere des Übergangszustandes im Bindungsprozess an InhA [7], was im Rückschluss zu einer ebenfalls verlangsamten Dissoziation des Enzym-Inhibitor-Komplexes führt. Zusätzlich wird dieser Effekt durch die Beschaffenheit des entsprechenden Substituenten an der 2‘-Position noch verstärkt oder abgeschwächt. Dies erfolgt beispielsweise durch eine Stabilisierung des Grundzustandes und eine daraus resultierende, verlängerte Verweildauer des Inhibitors am Enzym. Weitere, strukturelle Untersuchungen im Rahmen dieser Arbeit konnten den vorgeschlagenen Bindungsmodus [8] des neuartigen, speziell auf das ENR-Enzym von Staphylococcus aureus (saFabI) zugeschnittenen Inhibitors „55JS“ (auch „SKTS1“) bestätigen. Dieser Diphenyletherinhibitor besitzt an der 4‘-Position einen Pyridonring, welcher die Wechselwirkungen mit dem Enzym verstärken soll. Aus den strukturellen und vorläufigen, kinetischen Daten geht hervor, dass dieser Inhibitor ebenfalls und in ähnlicher Weise an InhA bindet. Außerdem legt ein Vergleich mit Komplexstrukturen verschiedener ENRs in Verbindung mit AFN-1252 [9] die Vermutung nahe, dass auch 55JS an weitere ENR-Homologe binden könnte; denn jener Teil des AFN-1252-Inhibitors, der sich räumlich mit dem Pyridonring von 55JS überlagert, geht mit derselben Region im Protein ähnliche Wechselwirkungen ein. Es ist daher möglich, dass dieser Inhibitor das Potential birgt, durch entsprechende Optimierung als Wirkstoff gegen andere Pathogene zum Einsatz zu gelangen. Beide dieser neuartigen, funktionellen Gruppen, die Triazol- und die Pyridongruppe, stellen einen guten Ansatzpunkt für die Weiterentwicklung von Diphenylethern bezüglich verbesserter kinetischer Eigenschaften gegenüber ENR-Enzymen dar. Ein weiterer, interessanter Ansatz für die strukturbasierte Wirkstoffentwicklung ist durch die Interaktionsfläche zwischen ENR-Enzymen und dem Acyl-Carrier-Protein (ACP) gegeben. ACP transportiert die naszierende Acylkette von einem zum nächsten Enzym des dissoziierten Fettsäurebiosynthesezyklus, welche es wahrscheinlich anhand elektrostatischer Interaktionen erkennt. Die Kontaktfläche zwischen saACP und saFabI wurde hier mittels verschiedener Ansätze untersucht, die sowohl Crosslinking-Experimente als auch die Generierung von Fusionsproteinen umfassten. In den verschiedenen Fusionskonstrukten wurden das ACP- und das ENR-Protein durch eine flexible Aminosäurekette unterschiedlicher Längen und Zusammensetzungen miteinander verbunden. Durch die Crosslinking-Experimente konnten Aminosäuren identifiziert werden, welche einen Teil einer vorgeschlagenen Interaktionsfläche [10] ausmachen und tatsächlich eine hohe Vernetzungseffizienz aufwiesen. Proteinkristalle des Komplexes, die entweder beide Einzelkomponenten oder das Fusionsprotein enthielten, zeigten jedoch nur schwache Beugungsmuster. Diese Beobachtung deckt sich mit der Annahme, dass die Komplexbildung äußerst kurzlebig ist. Die intrinsische Flexibilität beider Proteine erhöht zusätzlich die Schwierigkeit, wohlgeordnete Kristalle zu erhalten. Es wird deshalb notwendig sein, den Komplex in einem fixierten Zustand einzufangen. Die Verwendung eines hochaffinen Substrates, welches die Dissoziation des Komplexes unterbindet, beispielsweise ein acylgekoppelter Inhibitor [11] mit langer Verweildauer am Enzym, könnte hier von großem Nutzen sein und es damit erlauben eine detaillierte Kenntnis der ACP-FabI-Interaktionsfläche zu erhalten, die neue Perspektiven für eine gezielte Entwicklung von Inhibitoren der Fettsäurebiosynthese II eröffnen könnten.

During a two year period (2015/2016 and 2016/2017) two field trials were carried out on the Experimental farms of Almocreva (Beja) and Passinho (Elvas) respectively. The aim of these trials was to study the effect of a pre-emergence herbicide aclonifen (60%) applied in different doses in interaction with two water volumes, in the weed control and grain yield of chickpea (Cicer arietinumL.) crop. The herbicide doses studied were 1500, 1800, 2100 and 2400 g a.i. ha-1, corresponding the lower dose to the minimum recommended by the herbicide manufacturer for this crop, and the highest dose, to the maximum recommended. The water volumes were 300 and 400 L ha-1with the recommended application volume varying between 300 and 500 L ha-1. Both, doses and spray volumes used are recommended in Spain, being this herbicide in the final phase of approval for Portugal. There was a higher reinfestation at the second year of the trials, but the interaction year x dose x volume was not significant in relation to the grain yield per unit of area, with significant differences in this parameter, only to herbicide doses and to the interaction year x dose. The correlation between the efficacy of the herbicide and grain yield was highly significant for the two experimental years and different modalities (dose x volume). For each year, there was a significant correlation between seed yield per unit of area and number of pod per plant, plant height and number of seeds per unit of area. The opposite was registered regarding the number of plants per unit area and mean seed weight., Nos anos agrícolas de 2015/2016 e 2016/2017, realizaram-se dois ensaios de campo, na Herdade da Almocreva (Beja) e na Herdade do Passinho (Elvas), respetivamente. O objetivo destes ensaios foi estudar o efeito de diferentes doses do herbicida de pré-emergência aclonifena, em interação com dois volumes de calda, no controlo das infestantes e na produtividade da cultura do grão-de-bico (Cicer arietinumL.). As doses de herbicida estudadas foram 1500, 1800, 2100 e 2400 g s.a ha-1, correspondendo a dose menor à mínima recomendada pelo fabricante do produto para esta cultura e a dose mais elevada, à dose máxima recomendada. Os volumes de calda aplicados foram 300 e 400 L ha-1, com os volumes recomendados a variarem entre 300 e 500 L ha-1. Quer as doses, quer os volumes de calda usados, são recomendados em Espanha, estando este herbicida, em fase final de homologação para Portugal. Verificou-se, uma maior reinfestação no segundo ano de ensaio, mas a interação ano x dose x volume não foi significativa relativamente à produção de grão por unidade de área, havendo diferenças significativas relativamente a este parâmetro, apenas para as doses de herbicida e para a interação ano x dose. A correlação entre a eficácia do herbicida e a produção de grão foi altamente significativa para os dois anos de ensaio e diferentes modalidades (dose x volume). Em cada um dos anos de ensaio, a produção de grão por unidade de área está correlacionada significativamente com o número de vagens por planta, a altura das plantas e o número de sementes por unidade de área, o mesmo não sucedendo com o número de plantas por unidade de área e com o peso médio da semente.

The conversion of benzyl phenyl ether, diphenyl ether, diphenyl methane and biphenyl as representative model compounds for alpha-O-4, 5-O-4, alpha(1) (methylene bridges) and 5-5' lignin linkages was investigated. We compared the use of metal chlorides and acetates. The reactions were studied in sub- and supercritical water and supercritical ethanol between 300 and 400 degrees C. At low temperature in water, Lewis acids mainly catalyzed condensation of hydrolysis products of the dimeric model compounds. At higher temperature, mono-aromatic products were formed. The yield of monomeric products was higher in ethanol than in water. The preference for ethanol is due to extensive alkylation of the mono-aromatic products, which inhibits their condensation into larger products. The highest yields of deoxygenated mono-aromatics were obtained using Lewis acid catalysts at 400 degrees C in supercritical ethanol. The preferred Lewis acid catalysts were Fe, Cu, Ni and Al chlorides. (C) 2015 Elsevier B.V. All rights reserved.

Bu çalışma, çıkış öncesi ve çıkış sonrası kullanılan bir herbisit olan aclonifen’in farklı uygulama zamanının tilki kuyruğu (Alopecurus myosuroides Huds.) mücadelesinde %100 başarı sağlayan Kritik Konsantrasyon Değerlerine olan etkisini belirlemek amacıyla gerçekleştirilmiştir. A. myosuroides bitkileri sera koşullarında, saksılarda yetiştirilmiştir. Araştırmalarda, bitki bünyesindeki herbisit konsantrasyonunu hassas bir şekilde ölçmek için aclonifen süspansiyon konsantre (SC) formülasyonu Challenge 600’e 14C-aclonifen ilave edilmiş ve önerilen doz (270 g e.m. da-1 ) uygulanmıştır. Ekimler 2011 Mart-Nisan aylarında yapılmış, denemelerin kurulduğu ilk gün çıkış öncesi, takip eden 20’inci gün erken çıkış sonrası ve 40’ıncı gün geç çıkış sonrası uygulama yapılmıştır. Uygulamaları takip eden 10’uncu gün, bitkilerde görülen herbisit belirtileri gözlemlenmiş; yaprak yaş ve kuru ağırlıkları kaydedilmiştir. Sıvı sintilasyon cihazı kullanılarak her bir bitki yaprağındaki toplam radyoaktivite miktarı dpm cinsinden ölçülerek, aclonifen konsantrasyonu belirlenmiştir. Deneme bulguları, aclonifen’in önerilen dozunun A. myosuroides yapraklarında belirlenen aclonifen kritik konsantrasyonu çıkış öncesi için 1,58 ± 0,15 nmol/mg kuru ağırlık, erken çıkış ve geç çıkış sonrası uygulamalarında ise sırasıyla, 3,04 ± 0,27 ve 0,94 ± 0,15 nmol/mg kuru ağırlıktır. Deneme sonuçları, aclonifen’in önerilen dozu ile hem çıkış öncesi hem de A. myosuroides’in 1-2 yapraklı evresine kadar yapılacak erken çıkış sonrası uygulamalarında %100 oranında kontrol sağladığı, fakat bitkinin 3-4 yapraklı evresinden sonra yapılan uygulamalarda bitki gelişimini yavaşlatmasına rağmen etkisiz olduğu saptanmıştır., The objective of this study was to determine the effect of different treatments times of aclonifen, which is used as pre- and post-emergence herbicide in the control of blackgrass [Alopecurus myosuroides Huds. (Poaceae)] on the critical concentration values resulting in 100% success. The plants of A. myosuroides were grown on pots under greenhouse conditions. In the study, to determine the herbicide contraction on the plant tissues accurately, 14Caclonifen was added to the aclonifen suspension concentrate (SC) Challenge 600 and suggested dose (270 g e.m. da-1 ) was treated. The trials were initiated in march and april of 2011 and the treatments were applied the first (pre-emergence), 20th (early post-emergence) and 40th (later post-emergence) days. 10-day after each treatment, the symptoms were evaluated; and, the fresh and dry weights of the leaves were recovered. The aclonifen concentration on the fresh and dry leave samples were determined by the measuring the total radioactivity amount in dpm using liquid scintillation analyzer. The results of the trials indicated that the suggested doses of aclonifen critical concentration on the A. myosuroides leaves were: 1.58 ± 0.16 nmol/mg dry weight for pre-emergence; 3.04 ± 1.57 and 0.94 ± 0.81 nmol/mg dry weight for early and late post-emergence, respectively. It was also determined that the treatment of aclonifen with suggested dose when applied either as pre-emerge or as early post emergence until the plants reach 1-2 leaf stage before emergence or until 1-2 leaf stage result in 100% control; however, the treatments applied after 3-4 leaf stage are not successful although they result in delays of plant development.

International audience; Aclonifen belongs to the diphenylether (DPE) chemical family among which potent herbicides with a photodependent mode of action can be found. For years aclonifen has been used in several types of cultures. However its biochemical mode of action remains unclear although it was listed as a carotenoid synthesis inhibitor by the Herbicide Resistance Action Committee (HRAC). As a matter of fact, corn seedling leaves treated with 10(-4) M aclonifen and maintained in the dark no longer contained carotenoids but showed an accumulation of a compound having all the characteristics of phytoene. That demonstrated aclonifen ability to inhibit the desaturases catalyzing the transformation of phytoene into carotenoids. Moreover, aclonifen (5 x 10(-5) M) was responsible for a photordependent cell destruction (necrosis) of cucumber cotyledons typically due to protoporphyrin IX accumulation. The same phenomenon was demonstrated in aclonifen-treated etiolated corn seedlings (10(-4) M) that showed an accumulation of protoporphyrin IX, reaching 62 ng/g of leaf fresh mass and reactive oxygen species production under light. On these two cases (cucumber cotyledons and etiolated corn seedlings), aclonifen was acting as a typical DPE, as demonstrated by the accumulation of protoporphyrin IX. As a whole, aclonifen was shown here, to act on two different biochemical pathways including carotenoid synthesis on the one hand, as well as protoporphyrinogen oxidase, in the chlorophyll synthesis pathway, on the other for the same range of concentrations. (C) 2008 Elsevier Inc. All rights reserved.

National audience

The specific binding of the herbicide acifluorfen 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid to corn etioplast membranes is competitively inhibited by protoporphyrinogen IX, the substrate of protoporphyrinogen oxidase. Three other peroxidizing molecules, oxadiazon [5-ter-butyl-3-(2,4-dichloro-5-isopropoxyphenyl)-1,3,4-oxadiazol-2-one], LS 82556 [(S)3-N-(methylbenzyl)carbamoyl-5-propionyl-2,6-lutidine], and M&B 39279 [5-amino-4-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)pyrazol], also compete with acifluorfen for its binding site. The four herbicides thus bind to the same site, or to closely located sites, on the enzyme protoporphyrinogen oxidase.

Background & objectives: DPE-28, a substituted diphenyl ether (2,6-ditertiarybutyl phenyl-2’,4’-dinitro phenyl ether) was reported to exhibit promising insect growth regulating activity against Culex quinquefasciatus, the vector of lymphatic filariasis. A controlled release formulation (CRF) of DPE-28 has been developed to control Cx. quinquefasciatus in its breeding habitats. Toxicity of DPE-28, safety to non-target mosquito predators and the release profile of the CRF of DPE-28 are studied and discussed. Methods: The acute oral and dermal toxicity was tested in male and female Wistar rats as per the Organization for Economic Cooperation and Development (OECD) guidelines 425 and 402 respectively. The toxicity of DPE-28 to non-target predators was tested as per the reported procedure from this laboratory. The CRF of DPE-28 was prepared by following the reported procedure developed at this laboratory earlier. The concentration of DPE-28 released from the CRF was monitored by HPLC by constructing a calibration graph by plotting the peak area in the Y-axis and the concentration of DPE-28 in the X-axis. Results: DPE-28 has been tested for acute oral toxicity and found to be moderately toxic with LD50 value of 1098 mg/kg body weight (b.w). The results of the acute dermal toxicity and skin irritation studies reveal that DPE-28 is safe and non-irritant. DPE-28 when tested at 0.4 mg/litre against non-target mosquito predators did not produce any mortality. The release profile of the active ingredient DPE-28 from the CRF by HPLC technique showed that the average daily release (ADR) of DPE-28 ranged from 0.07 to 5.0 mg/litre during first four weeks. Thereafter the matrix started eroding and the ADR ranged from 5 to 11 mg/litre during the remaining 5 wk. The cumulative release of active ingredient showed that > 90 per cent of the active ingredient was released from the matrix. Interpretation & conclusions: The controlled release matrix of DPE-28 was thus found to inhibit the adult emergence (>80%) of Cx. quinquefasciatus for a period of nine weeks. The CRF of DPE-28 may play a useful role in field and may be recommended for mosquito control programme after evaluating the same under field conditions.