Sub-MICs of Mentha piperita essential oil and menthol inhibits AHL mediated quorum sensing and biofilm of Gram-negative bacteria

Bacterial quorum sensing (QS) is a density dependent communication system that regulates the expression of certain genes including production of virulence factors in many pathogens. Bioactive plant extract/compounds inhibiting QS regulated gene expression may be a potential candidate as antipathogenic drug. In this study anti-QS activity of peppermint (Menthe piperita) oil was first tested using the Chromobacterium violaceum CVO26 biosensor. Further, the findings of the present investigation revealed that peppermint oil (PMO) at sub-Minimum Inhibitory Concentrations (sub-MICs) strongly interfered with acyl homoserine lactone (AHL) regulated virulence factors and biofilm formation in Pseudomonas aeruginosa and Aeromonas hydrophila. The result of molecular docking analysis attributed the QS inhibitory activity exhibited by PMO to menthol. Assessment of ability of menthol to interfere with QS systems of various Gram-negative pathogens comprising diverse AHL molecules revealed that it reduced the AHL dependent production of violacein, virulence factors, and biofilm formation indicating broad-spectrum anti-QS activity. Using two Escherichia colt biosensors, MG4/pKDT17 and pEAL08-2, we also confirmed that menthol inhibited both the las and pqs QS systems. Further, findings of the in vivo studies with menthol on nematode model Caenorhabditis elegans showed significantly enhanced survival of the nematode. Our data identified menthol as a novel broad spectrum QS inhibitor.

Germinação de sementes de atemoia (Annona Cherimola Mill. x A. squamosa L.) cv 'Gefner' submetidas a tratamentos com ácido Giberélico (GA3) e ethephon

O objetivo deste trabalho foi estudar os efeitos do ácido giberélico (GA3), do ethephon e da interação de ambos os reguladores vegetais no processo germinativo de sementes de atemoia (Annona cherimola Mill. x A. squamosa L. ), cultivar 'Gefner'. Empregou-se delineamento experimental inteiramente casualizado, em esquema fatorial 5², com os tratamentos constituídos pela combinação de cinco concentrações de GA3 (ácido giberélico) e cinco concentrações de ethephon, resultando em 25 tratamentos, com quatro repetições de 25 sementes por parcela. As concentrações de GA3 empregadas foram: 0; 250; 500; 750 e 1.000 mg L-1 i.a.e de ethephon: 0; 25; 50; 75 e 100 mg L-1 i.a.. Os tratamentos com os reguladores vegetais foram aplicados na semente por imersão das mesmas nas soluções de GA3 e ethephon por período de 36 horas. As sementes foram semeadas em rolo de papel germitest e levadas à câmara de germinação onde permaneceram no escuro, com temperatura alternada entre 20ºC por 8 horas e 30ºC por 16 horas. As variáveis avaliadas foram: percentagem, tempo e índice de velocidade de germinação, percentagem de pl��ntulas normais e percentagem de sementes dormentes. Existe interação da ação dos reguladores vegetais estudados no processo germinativo de sementes de atemoia, o que permite concluir que a percentagem de germinação de sementes de atemoia (Annona cherimola Mill. x A. squamosa L. ) cv 'Gefner' é aumentada com o emprego de 778 mg L-1 de GA3, enquanto a associação entre elevadas concentrações de GA3 e 75 a 100 mg L-1 de ethephon incrementam o índice de velocidade de germinação e a percentagem de pl��ntulas normais.

Silicon location through backscattered electron imaging and X-ray microanalysis in leaves of Cyperus ligularis L. and Rhynchospora aberrans C. B. Clarke (Cyperaceae)

(Silicon location through backscattered electron imaging and X-ray microanalysis in leaves of Cyperus ligularis L. and Rhynchospora aberrans C. B. Clarke (Cyperaceae)). The Cyperaceae show the ability to incorporate silicon by depositing colloidal silica, which is recorded by the occurrence of projections in the form of cones, in inner tangential walls of some epidermal cells or "silica cells". Leaves of C. ligularis and R. aberrans were analyzed through the technique of electron backscatter. Cyperus ligularis accumulates silica, in addition to "silica cells", in some stomata, trichomes and the cell walls that surround the cavities of the aerenchyma. The silica in the latter occurs in various forms; however, the cells located near the vascular bundles have conical projections, similar to those of the epidermis. Rhynchospora aberrans presents "silica cells" whose projections have tapered "satellites". In this species, silica also occurs in stomata and certain epidermal cells adjacent to them. It appears that the silicon deposition occurs in combination with the wall (with no apparent structural changes), and structures of secretion, or projections of the wall. These structural changes in the species, and location, are probably related to functional and environmental factors, especially the soil, in addition to relation with taxonomic groups.

Synthese von polymergebundenen Sialyl-Lewis x-Strukturen und deren Mimetika als Zelladhäsionsinhibitoren für E-, L- und P-Selektin

Kohlenhydrate dienen nicht nur der Ernährung oder der Stabilisierung von Zellwänden, sondern sie sind auch von essentieller Bedeutung für Zell-Zell-Wechselwirkungen im Organismus. Damit sind sie von besonderem Interesse für die Behandlung von Entzündungen sowie tumorösen Erkrankungen, die auf Wechselwirkungen zwischen bestimmten Kohlenhydraten und Rezeptoren, Selektine genannt, basieren. Die vorliegende Dissertation mit dem Titel „Synthese von polymergebundenen Sialyl-Lewis x-Strukturen und deren Mimetika als Zelladhäsionsinhibitoren für E-, L- und P-Selektin“ befasst sich mit der Synthese und der Modifizierung des natürlich vorkommenden Selektin-Liganden Sialyl-Lewisx und seinen potentiell mimetischen Strukturen auf Basis von Gemischen der an der Bindung beteiligten Kohlenhydrate sowie von sulfatierten Einheiten. Um im Organismus eine verstärkte Bindung an die zu adressierenden Rezeptoren und eine erhöhte Zirkulationsdauer zu erreichen, wurden die geeignet funktionalisierten Liganden mittels reaktiver Polymere auf Basis von Pentafluorphenyl-Reaktivestern im Rahmen einer polymeranalogen Umsetzung an ein definiertes Methacrylamid-Polymer gebunden.Um die biologische Wirksamkeit der synthetisierten Polymere zu überprüfen, wurden Oberfl��chenplasmonenresonanz-Messungen (SPR-Messungen) durchgeführt. Dabei zeigte sich bei den verschiedenen Selektinen eine unterschiedlich hohe Affinität der Sialyl-Lewis x sowie der mimetischen Polymere. Es konnten bei E-Selektin die geringsten, bei L-Selektin mittlere und bei P-Selektin die höchsten Affinitäten im unteren nanomolaren Bereich festgestellt werden.

Stachys alpina L. x Stachys silvatica L.

Von Joh. Feld

Fertilización foliar con macronutrientes a plantas de naranja Valencia late (Citrus sinensis (L.) Osbeck) y tangor Murcott (Citrus reticulata Blanco x Citrus sinensis (L.) Osbeck)

El objetivo de este trabajo fue analizar el efecto de diferentes dosis de fertilizantes foliares con macronutrientes en plantas de naranja Valencia y de tangor Murcott. Los experimentos fueron realizados durante tres campañas consecutivas en Corrientes Argentina. El diseño experimental fue en bloques completos al azar con cuatro repeticiones y parcelas experimentales de cuatro plantas. Los tratamientos ensayados fueron T1 control; T2 N (12%) 2 L.ha-1; T3 N (12%) 4 L.ha-1; T4 N (9%) y P (2,6%) 2 L ha- 1; T5 N (9%) y P (2,6%) 4 L.ha-1; T6 N (9,3%), P (2,6%) y K (2,1%) 2 L.ha-1; T7 N (9,3%), P (2,6%) y K (2,1%) 4 L.ha-1, de fertilizante foliar formulados en base a sales de sulfato de amonio, fosfato monoamónico y nitrato de potasio según tratamiento. Los mismos fueron aplicados por campaña en prefloración, plena floración y en otoño. Se midieron las concentraciones foliares de N, P y K en hojas de otoño de ramas fructíferas y al momento de cosecha se determinó rendimiento total, diámetro de fruta, porcentaje de jugo, sólidos solubles, acidez y relación sólidos solubles/acidez. En Valencia late todos los tratamientos incrementaron el contenido de P foliar en comparación con el control. El tratamiento T7 incrementó un 38,7% el rendimiento respecto de T1, aunque los frutos presentaron menor diámetro. En "Murcott" todos los tratamientos incrementaron el rendimiento comparados con T1, y las máximas producciones se observaron en los tratamientos T7 (64,9% mayor) y T6 (43,8% mayor) además T7 incrementó el contenido de P foliar y disminuyó el contenido de sólidos solubles en comparación con el control. La fertilización foliar con macronutrientes incrementó la productividad en naranja Valencia late y tangor Murcott. Este trabajo muestra la utilidad de la fertilización foliar con macronutrientes como una herramienta complementaria en los programas de fertilización diseñados para optimizar el rendimiento.

Biomass and essential oil yields of cornmint (Mentha arvensis L.) grown in the irrigation area of Río Dulce, Santiago del Estero, Argentina.

The aim of this study is to determine the yield and composition of the essential oil of cornmint (Mentha arvensis L.) grown in the irrigation area of Santiago del Estero, Argentina. Field tests were carried out under irrigation conditions, harvesting when 70% flowering was reached (in the summer and at the end of the winter seasons). Essential oil yields were 2% in the first cut and 1.6% in the second cut, respectively, the major constituents of the essential oil being menthol, menthone, isomenthone and menthofuran. In both cases, a high concentration of menthol was obtained, although during the winter the content decreased, increasing the concentration of menthofuran. It is concluded that during the summer a higher yield and better quality of essential oil are produced.