Chemical and morpho-functional aspects of the interaction between a Neotropical resin bug and a sticky plant

Rubus adenotrichos is an Andean blackberry plant bearing glandular trichomes which secrete an adhesive exudate. The resin bug Heniartes stali is frequently found on this plant and collects this exudate using the forelegs to enhance its preying capacity. Here, we describe the morphology of the plant's glandular trichomes with the aid of light and scanning electron microscopy, as well as the chemical components of the exudate by histochemical and gas chromatography-mass spectrometry analysis. We have also combined behavioral observations with the analysis of the insect leg morphology to identify possible morpho-functional adaptations evolved by H. stali for collecting the sticky secretions. Glandular trichomes exhibited a multicellular long stalk and a calyx-shaped head with radially aligned cells. The composition of the resinous fluid was mainly terpenes and phenolics, which may contribute to its sticky properties. Brush-like structures on the tibia of forelegs in H. stali suggests an adaptive trait for collecting the trichomes exudate. A profusely hair-covered area on metatibiae operated as a resin storage structure. Abundant pore-like openings were observed in the cuticle of this area through which substances could be conceivably secreted to prevent resin hardening. These findings combine morphological and chemical features of a fascinating insect-plant interaction in the Neotropics.

Rubus adenotrichos es una planta de mora andina que contiene tricomas glandulares los cuales secretan un exudado pegajoso. El chinche de las resinas Heniartes stali se encuentra con frecuencia en esta planta recogiendo el exudado con sus patas delanteras para mejorar su capacidad en la captura de las presas. En este trabajo empleamos microscopía de luz y microscopía electrónica de barrido para describir la morfología de los tricomas. Los constituyentes químicos del exudado fueron estudiados mediante técnicas histoquímicas, de cromatografía de gases y espectrometría de masas. También combinamos observaciones del comportamiento del insecto en la recolección y almacenamiento del exudado con el análisis de la morfología de sus patas, empleando microscopía de luz y microscopía electrónica de barrido para identificar las posibles adaptaciones morfo-funcionales desarrolladas para la manipulación de estas secreciones adhesivas. Los tricomas glandulares exhibieron un tallo largo multicelular y una cabeza glandular en forma de cáliz con células alineadas radialmente. El fluido resinoso estaba compuesto principalmente por terpenos y compuestos fenólicos, los cuales parecen contribuir con sus propiedades adhesivas. La presencia de estructuras tipo pincel en las puntas de las tibias de las patas delanteras sugieren un carácter adaptativo para recoger el exudado de los tricomas. También describimos un área en las patas traseras profusamente cubierta de pelos, que funcionaban como estructuras de almacenamiento de la resina. En la cutícula de éstas observamos abundantes aberturas similares a poros y sugerimos que a través de ellos se secretan sustancias que impiden el endurecimiento de la resina almacenada. Estos hallazgos aportan información sobre características morfológicas y químicas de un novedoso modelo de interacción insecto-planta en el neotrópico.

Qualitative Study on the Production of the Allelochemicals Benzoxazinones by Inducing Polyploidy in Gramineae with Colchicine.

The possibility of inducing polyploidy in grasses by treatment with colchicine and its effect on the production and root exudate content of 2,4-dihydroxy-7-methoxy-2 H-1,4-benzoxazin-3-one (DIMBOA) and 2,4-dihydroxy-2 H-benzoxazin-3-one (DIBOA) was studied in wheat, corn, and rye. Caryopses treated with colchicine at concentrations in the range of 0.1-10 mg/mL for 8 and 48 h and with inoculation of the growth medium are markedly affected in terms of both the distribution and concentration levels of allelochemicals in plants. A greater accumulation was observed in the root with respect to the stem, and this increased with an increasing concentration of colchicine and with treatment time. Analysis of the compounds released by root exudates showed that treatment with colchicine at a concentration higher than 1 mg/mL caused a significant increase in the concentrations of allelochemicals measured in the growth medium. It is proposed that treatment with colchicine of seedling caryopses mixoploids plant populations and that the overall effect is an increase in the levels of allelochemicals released. The ecological implications of this behavior are discussed along with the impact of plant-plant interactions (allelopathy).

Human gastric cancer, Helicobacter pylori and bracken carcinogens: A connecting hypothesis.

Long term infection of Helicobacter pylori (Hp) virulent strains is a key factor in the genesis of human gastric cancer, and so are certain dietary proinflammatory and genotoxic compounds. Carcinogenic bracken fern (Pteridium spp.) is one of these. Toxins from this plant are consumed as bracken culinary preparations, through milk and meat of bracken-exposed livestock, and drain waters from bracken swards. Bracken toxin ptaquiloside (PtQ), a suspected human carcinogen, elicits complex responses in animals leading to death. PtQ and Hp might cooperate in gastric pathologies. This paper presents an hypothesis on PtQ-Hp association leading to the enhancement of carcinogenesis in the human gastric environment that might explain the high gastric cancer incidence and death rates among Hp-infected people living in bracken zones at two levels: (1) The macroscopic scale comprising the flow of PtQ in the human diet. (2) the microscopic scale encompassing (A) gastric luminal medium; (B) gastric mucus structure and mucin degradation elicited by Hp; (C) bacterial pH gradient modification of the gastric mucosa that favors PtQ survival and its penetration into epithelial tissue; (D) combined PtQ/Hp effects on gastric immune and inflammatory responses; (E) PtQ-Hp complementary activity at selected cell signaling cascades and genome disturbance.

Tetraoxanes as a new class of efficient herbicides comparable with commercial products.

BACKGROUND: Several 1,2,4,5-tetraoxanes were synthesised, and their herbicidal activity was tested against weeds and compared with the activity of commercial herbicides glyphosate and imazethapyr. RESULTS: The compounds were prepared by reacting carbonyl compounds with hydrogen peroxide under acid catalysis, affording 1,1-dihydroperoxides (36-91%) that were further converted into 1,2,4,5-tetraoxanes (10-52%) under similar reaction conditions. All products were evaluated against Sorghum bicolor and Cucumis sativus at 0.0125-1.0 mM, and several tetraoxanes caused >70% inhibition of the growth of roots and aerial parts. The most active products were evaluated against the weeds Sorghum arundinaceum, Euphorbia heterophylla, Brachiaria brizantha and Bidens pilosa. Some compounds were highly effective (>80% inhibition at 1.0 mM) against the weeds, showing activity comparable with that of glyphosate or imazethapyr. One of the tetraoxanes was selective, being inactive against dicotyledonous species while inhibiting the roots and aerial parts of monocotyledonous species by 92.9-97.5%, which is comparable with the effect of glyphosate. CONCLUSIONS: Tetraoxanes constitute a new class of effective herbicides with great potential for commercial development.

Diterpene Foliar exudates of Blakiella bartsiifolia and phytotoxicity of clerodanes.

Blakiella bartsiifolia (S.F. Blake), an endemic and rare high altitude plant of the northern Andes, appears well adapted to the prevailing harsh environment owing in part to a thick glandular trichome cover. From foliar exudates, two new clerodanes, 15,16-epoxy-2-hydroxy-3,13(16),14-clerodatrien-20-oic acid (bartsiifolic acid) (2) and Z-15,16-dihydroxy-3,13-clerodien-20-oic acid (barthydrolic acid) (3), were isolated in addition to the known junceic acid (1). In addition, three new alicyclic furanoditerpenes: 1,20-epoxy-1,3(20),6(E),10(E),14-phytapentaen-18-methyl-19-oic acid (blakielic acid) (4), 1,20-epoxy- 1,3(20),10(E),14-phytapentaen-18-methyl-19-oic acid (blakifolic acid) (5) and 1,20-epoxy-1,3(20),6,14-phytatetraen-19-methyl-18-oic acid (dihydrocentipedic acid) (6) were obtained in minor quantity. Seed germination and plantlet growth bioassays on Allium cepa and Lactuca sativa to monitor bioactivity during isolation procedures revealed compounds 1-3 with substantial inhibition comparable with synthetic linuron.

Evidence for an allelopathic interaction between rye and wild oats.

Allelopathy is a biological phenomenon in which an organism produces one or more biochemicals that influence the growth, survival, and reproduction of other organisms. Allelopathy has been the subject of a great deal of research in chemical ecology since the 1930s. The characterization of the factors that influence this phenomenon has barely been explored, mainly due to the complexity of this area. The main aim of the research carried out to date has been to shed light on the importance of these interactions in agroecosystems, especially in relation to the interactions between crops and weeds. Herein we report the characterization of a complete allelochemical pathway involving benzoxazinones, which are known to participate in allelopathic plant defense interactions of several plants of high agronomic interest. The production of the defense chemicals by a donor plant (crop), the route and transformations of the chemicals released into the environment, and the uptake and phytotoxic effects on a target plant (weed) were all monitored. The results of this study, which is the first of its kind, allowed a complete dynamic characterization of the allelopathic phenomenon for benzoxazinones.

Comparative profiles of Achyrocline alata (Kunth) DC. and A. satureioides (Lam.) DC., Asteraceae, applying HPLC-DAD-MS / Perfil comparativo entre Achyrocline alata (Kunth) DC. e A. satureioides (Lam.) DC., Asteraceae, utilizando HPLC-DAD-MS

A comparative analysis between the hydromethanolic extracts of Achyrocline alata (Kunth) DC. and A. satureioides (Lam.) DC., Asteraceae, was performed by the use of HPLC-DAD-MS. Both plants were used without distinction and under the same indications in folk medicine in Mato Grosso do Sul, Brasil. While Achyrocline alata ("jatei-ka-ha") is used in folk medicine of the Brazilian state of Mato Grosso do Sul, A. satureioides is predominantly used in other states. Samples of both plants collected in different periods, 1996 and 2002, showed a very similar chemical profile. The results indicate that A alata could be used in phytotherapeutic preparations as substitue for A. satureioides, since they have similar chemical compositions of the polar extract.

Análises comparativas entre os extratos hidrometanólico de Achyrocline alata (Kunth) DC. e A. satureioides (Lam.) DC., Asteraceae,foram desenvolvidas utilizando HPLC-DAD-MS. Ambas as plantas são utilizadas indistintamente para as mesmas indicações na medicina popular de Mato Grosso do Sul, Brasil, enquanto a A. alata ("jatei-ka-há) é predominante neste estado, a A. satureioides ("marcela") é predominante nos demais estados da Federação. Amostras das duas espécies coletadas em épocas diferentes, 1996 e 2002, apresentaram o mesmo perfil cromatográfico. O presente resultado pode justificar que A. alata possa ser utilizada como sucedânea de A. satureioides, pois apresentam similar composição de metabólitos secundários polares.

Reduced photosynthetic activity is directly correlated with 2-(3H)-benzoxazolinone accumulation in lettuce leaves.

2-(3H)-benzoxazolinone (BOA) is a secondary plant metabolite previously found to inhibit plant growth and development. The phytotoxic activity of BOA has been extensively demonstrated over the last years. However, the relation of BOA phytotoxicity with BOA accumulation in plant leaves has not been thoroughly investigated. In this work, BOA phytotoxicity on photosynthesis (PhiPSII and Pn) of lettuce (Lactuca sativa L. cv. Great Lakes) was studied, and these results were correlated with BOA quantities in the leaves. BOA-treated plants showed reduced photosynthesis rate 6 h after the beginning of the treatment, and the efficiency of photosystem II started to be affected 10 h after treatment. These results were correlated with an increasing concentration of BOA in leaves that starts 6 h after treatment and shows a maximum at 96 h.

Rediscovering the bioactivity and ecological role of 1,4-benzoxazinones.

Compounds of the (2H)-1,4-benzoxazin-3(4H)-one class have attracted the attention of phytochemists since the first isolation of 2,4-dihydroxy-2H-1,4-benzoxazin-3(4H)-one (DIBOA) and 2,4-dihydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one (DIMBOA). Extensive research has been carried out on the isolation and synthesis of these materials as well as on the dynamics of their degradation in different systems. This has led to the discovery of a wide variety of compounds that are of high interest from the point of view of phytotoxic, antifungal, antimicrobial, and antifeedant effects among others. The potential application of benzoxazinones and their derivatives as leads for natural herbicide models is a topic of current interest. Furthermore, the importance of degradation on the ecological behaviour of benzoxazinone-producing plants is also being realised, and proposals concerning the role of the degradation products in chemical defence mechanisms have been put forward. There is also increasing interest in the improvement of analytical methodologies, and ecotoxicologic effects, toxicity on target and non-target organisms, and degradation kinetics are also being addressed. The development of new phytotoxicity bioassay techniques represents one of the most important breakthroughs in this respect. Moreover, benzoxazinones and some of their derivatives have been employed in the development of pharmaceuticals. The versatility of the benzoxazinone skeleton, in addition to its relative chemical simplicity and accessibility, makes these chemicals amongst the most promising sources of bioactive compounds that are natural in origin.

ESTUDIO POR ESPECTROFOTOMETRÍA UV-Vis DE LA REACCIÓN ENTRE LOS IONES CIANURO Y PICRATO. UN EJEMPLO PRÁCTICO DE APLICACIONES ANALÍTICAS Y ESTUDIOS CINÉTICOS / Uv-vs spectrophootometry study of the reaction between cianide ions and picrate. a practical example of analytical applications and kinetic studies / Estudo por espectrofotometria uv-is da reação entre os ions cianeto e picrato. uum exemplo prático de aplicações analíticas e estudos cinéticos

La cinética de la reacción entre los iones cianuro y picrato se estudió por espectro-fotometría UV-Vis. Se observó una reacción de orden uno para ambos reactivos, así como un desplazamiento batocrómico de la señal de máxima absorbancia, incrementando la concentración de cualquiera de los reactivos, asociada a la formación de complejos de diferente estequiometría y resultando en los consiguientes cambios en los parámetros espectrométricos. Estos resultados sustentan una interacción de tipo π para el complejo resultante, resultado que se pudo generalizar utilizando otras moléculas donadoras que muestran las posibles interferencias de algunos compuestos químicos en las determinaciones cualitativas y cuantitativas de la frecuencia cianogénica y la determinación cuantitativa de glucósidos cianogénicos en plantas.

The kinetics of the cianide-picrate reaction was studied on the basis of UV-Vis spectrophotometry. A first order reaction was found for each reagent. It was also observed a batocromic displacement of the maximum absorbance wavelength, by increasing the concentration of any of the reagents, this result is associated to the formation of different stoichiometry complexes and the subsequent spectrometric parameters change. These results support the existence of an interaction of the π kind for the resulting complex, and a parallel result was obtained by using other π electron donor molecules. This displays the evidence of plausible interferences of some chemicals in qualitative and quantitative analytical applications of this reaction, specially of those used in the cianogenic frequence and quantitaive cianogenic glycosides determination in plants.

A cinética da reação entre o íon cianeto e o picrato de sódio foi acompanhada por espectrofotometria no UV/Vis. Foi observada uma reação de primeira ordem para ambos reagentes, bem como um deslocamento batocrômico no Dmax, aumentando-se a concentração de qualquer um dos reagentes, associa-se a ela, a formação de complexos de diferentes estequiometrias e, consequentemente, mudanças nos parâmetros espectrométricos. Estes resultados sustentam a possibilidade de uma interação do tipo π para o complexo resultante e que pode ser aplicada, de forma generalizada, para outras moléculas doadoras, evidenciando possíveis interferências de alguns compostos químicos com as determinações qualitativa e quantitativa de derivados cianogênicos, bem como a determinação quantitativa de derivados glicosilados cianogênicos em plantas.