Absorption and Elimination of the Allelochemical MBOA by Weeds during Seedling Growth

6-Methoxy-2-benzoxazolinone (MBOA) is an allelochemical that is found in Poaceae and is generally associated with monocotyledon species. This compound is formed from the glycosylated form of 2,4-dihydroxy-(2H)-1,4-benzoxazin-3(4H)-one (Gly-DIMBOA) by a two-stage degradation process. The MBOA detoxification capacity of two weed species, namely Echinochloa crus-galli and Lolium rigidum, and a resistant biotype of Lolium rigidum (SLR31) was studied both qualitatively and quantitatively. The product of metabolism is similar for both weed species. This finding indicates that these weeds probably metabolize xenobiotics by an identical route, since the product detected was the same in both cases. Kinetic studies on the absorption and translocation to the shoot showed differences in these processes depending on the species. The analysis of treated plants, which were subsequently transplanted to a growth medium without xenobiotic compound, showed that the weeds studied are capable of transmitting the previously absorbed compound to the medium by root exudation. The results show that this process is another defense mechanism of plants facing external threats

Soil biodegradation of a benzoxazinone analog proposed as a natural products-based herbicide

Aims Benzoxazinones with the 4-hydroxy-(2H)-1,4- benzoxazin-3(4H)-one skeleton have been proposed as potentially successful models for the development of novel design leads. D-DIBOA has proven to be the most promising base structure in the search for novel herbicide models based on the benzoxazinone skeleton. The biodegradation dynamics of D-DIBOA in soil are therefore relevant and are the subject of this study. Methods A previously optimized methodology for the assessment of biodegradation has been applied for the first time to a synthetic benzoxazinone. Results Biodegradability is a characteristic of natural benzoxazinones and a safety requirement for the development of herbicidal chemicals. The biodegradation phenomenon and its consequences for the development of new herbicide models are discussed. The half-life determined for D-DIBOA was much higher than those previously reported for the natural products DIBOA, DIMBOA and their benzoxazolinone derivatives. Conclusions This finding, together with its previously described potent phytotoxicity, suggests that D-DIBOA is a useful candidate for novel herbicide model development. The lactam D-HBOA, which is slightly less phytotoxic than its precursor, was discovered to be the first and principal metabolite resulting from D-DIBOA degradation

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

Información Investigador: Oliveros Bastidas, Alberto de Jesús

Doctorado5789II - 2005; Candidato - 200381 - 2005; 35 - 2003; 13 - 2001Aislamiento, elucidación extructural y actividad biológica de productos de origen natural. Desarrollos de bioensayos en estudios alelopáticos.Abril de 2007Lic. en Química+58 274 2401386Facultad de [email protected]

A method for the practical quantification and Kinetic evaluation of Cyanogenesis in plant material. application to Pteridium aquilinum and Passiflora capsularis.

A method for the practical quantification and Kinetic evaluation of Cyanogenesis in plant material. application to Pteridium aquilinum and Passiflora capsularis (Alonso Amelot, Miguel and Oliveros, Alberto) Abstract A procedure for the quantitative determination of hydrogen cyanide (HCN) released by plants has been developed based on the UV-vis spectrum of the sodium picrate-cyanide complex. Fresh plant tissue mixed with toluene was placed in a gas flow system designed to carry the evolved HCN through 2,4- dinitrophenylhydrazine solution in acidic water:ethanol to trap interfering volatile carbonyl derivatives, and then into an alkaline solution of sodium picrate. After 18 h of gas flow at a rate of 6 mL/min, the absorbance of the solution was measured at 500 nm and the concentration of HCN was determined by calibration in the range 10-3 - 10-5 M. The molar absorptivity coefficient (1.385 L/cm M) yielded a detection limit of 2.6 x 10-6 mol/L and a 92.6 ± 2.6% recovery yield of HCN. The method was applied to determine the cyanide release capacity of Passiflora capsularis (up to 3.34 mg of HCN/g fresh plant tissue), and of croziers of Pteridium aquilinum var arachnoideum (10.4-61.3 mg of prunasin/g fresh plant tissue), and its rate of HCN production (K = 2.20 ± 0.01 x 10-4/s). Cymbopogon citratum, known to release large quantities of volatile, potentially interfering, monoterpene ketones and aldehydes, gave a negative reaction. Copyright © 2000 John Wiley & Sons, Ltd. This article was published on Phytochemical Analysis Phytochem. Anal. 11, 309-316 (2000)[email protected]@ula.veNivel monográfic

Cyanogenic polimorphysm in brackens, Pteridium arachnoideum and P. caudatum, from the northern Andes

Cyanogenesis in Pteridium caudatum and P. arachnoideum has been examined. Samples of the Andes of South America furnished from 0 to 4.63 mg of prunasin g-1 of frond dry weight (dw) in P. caudatum and from 0 to 103 mg of g-1 dw in P. arachnoideum. In both fern species the continuous distribution of prunasin suggested cyanogenic polymorphism. The frequency of cyanogenic morphs was 84.7% for P. caudatum and 98.6% for P. arachnoideum. Cyanogenic activity was highest in the young crozier and waned rapidly with frond growth. The crozier head was found to yield HCN much more than the stipe

Estudio por espectrofotometria uv-vis de la reacción entre los iones cianuro y el picrato. un ejemplo práctico de aplicaciones analiticas y estudios cinéticos

La cinética de la reacción entre el ión cianuro y el picrato de sodio se estudió por espectrofotometría 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 p 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

Phenolics and condensed tannins of high altitude Pteridium arachnoideum in relation to sunlight exposure, elevation, and rain regime.

Phenolics and condensed tannins of high altitude Pteridium arachnoideum in relation to sunlight exposure, elevation, and rain regime. (Alonso Amelot, Miguel; Oliveros Bastidas, Alberto y Calcagno P., María Pía) Abstract Non-adapted plants growing in high altitude such as bracken fern Pteridium arachnoideum are exposed to environmental extremes that may induce a chemical adaptive response. Here we show that there is a non-uniform distribution of low (LMP) and high molecular weight (HMP) phenolics in the frond parts of P. arachnoideum growing at high elevation. LMPeHMP levels were measured in sun-exposed (E) and self shaded (SS) pinnae between 2100 and 3190 m in the tropical Andes, during dry and rainy seasons. While there was no difference in E vs. SS contents of LMP at 2100 m, E accumulated greater LMPeHMP concentrations relative to SS as altitude increased. This difference was increased during the dry season. Linear correlations between the position of each pinnae relative to the ground level and LMPeHMP occurred along a 2570e3190 m transect. Water restriction in the dry season also caused increase of LMP and HMP.We conclude that excess UV-B radiation and water availability are important modelers of the non-adapted plant acclimation response to stress in tropical high mountain [email protected]@[email protected] monográfic

Optimization of Benzoxazinones as natural herbicide models by Lipophilicity enhancement.

Optimization of Benzoxazinones as natural herbicide models by Lipophilicity Enhancement. (Macías, Francisco A.; Marín, David; Oliveros Bastidas, Alberto y Molinillo G., José Abstract Benzoxazinones are plant allelochemicals well-known for their phytotoxic activity and for taking part in the defense strategies of Gramineae, Ranunculaceae, and Scrophulariceae plants. These properties, in addition to the recently optimized methodologies for their large-scale isolation and synthesis, have made some derivatives of natural products, 2,4-dihydroxy-(2H)-1,4-benzoxazin-3-(4H)-one (DIBOA) and its 7-methoxy analogue (DIMBOA), successful templates in the search for natural herbicide models. These new chemicals should be part of integrated methodologies for weed control. In ongoing research about the structure-activity relationships of benzoxazinones and the structural requirements for their phytotoxicity enhancement and after characterization of the optimal structural features, a new generation of chemicals with enhanced lipophilicity was developed. They were tested on selected standard target species and weeds in the search for the optimal aqueous solubility-lipophilicity rate for phytotoxicity. This physical parameter is known to be crucial in modern drug and agrochemical design strategies. The new compounds obtained in this way had interesting phytotoxicity profiles, empowering the phytotoxic effect of the starting benzoxazinone template in some cases. Quantitative structure-activity relationships were obtained by bioactivity-molecular parameters correlations. Because optimal lipophilicity values for phytotoxicity vary with the tested plant, these new derivatives constitute a more selective way to take advantage of benzoxazinone phytotoxic [email protected]@ula.veNivel monográfic