Structure-activity relationship studies of the phytotoxic properties of the diterpenic moiety of breviones.

Background: Brevianes are a family of bioactive meroterpenoids originally described in fungi of the family Penicillium. These compounds have attracted a great deal of interest not only because of their unusual skeleton, suggesting a mixed mevalonate and polyketide biogenetic pathway, and their unusual oxa-spiro ring fused to an α-pyrone, but also because of the bioactivities shown by many members of this family.

Results: During the course of a project aimed at the total synthesis of natural breviones A to E, the authors were able to synthesise the diterpenic moiety of brevianes and abeo-brevianes.

New chemical clues for broomrape-sunflower host-parasite interactions: synthesis of guaianestrigolactones.

A comparative structure-activity relationship (SAR) study has been conducted with several guaianolide sesquiterpene lactones (SLs) as inducers of the germination of sunflower broomrape (Orobanche cumana) seeds. Compounds were selected and synthesized to study the influence of the lactone-enol-gamma-lactone moiety on the selectivity of SLs toward the stimulation of sunflower broomrape germination. The results clearly illustrate that SLs are recognized only by O.

Evolution and current status of ecological phytochemistry.

Phytochemical studies have experienced a great deal of change during the last century, not only regarding the number of compounds described, but also in the concept of phytochemistry itself. This change has mainly been related to two key points: the methodologies used in phytochemical studies and the questions regarding 'why secondary metabolites appeared in plants and in other living organisms?' and 'what is their role?'. This transformation in the field has led to new questions concerning such different subjects as evolution, paleobotany, biochemistry, plant physiology and ethnography.

Allelopathy--a natural alternative for weed control.

Allelopathy studies the interactions among plants, fungi, algae and bacteria with the organisms living in a certain ecosystem, interactions that are mediated by the secondary metabolites produced and exuded into the environment. Consequently, allelopathy is a multidisciplinary science where ecologists, chemists, soil scientists, agronomists, biologists, plant physiologists and molecular biologists offer their skills to give an overall view of the complex interactions occurring in a certain ecosystem. As a result of these studies, applications in weed and pest management are expected in such different fields as development of new agrochemicals, cultural methods, developing of allelopathic crops with increased weed resistance, etc.

Application of Hansch's model to guaianolide ester derivatives: a quantitative structure-activity relationship study.

A quantitative structure-activity study to evaluate the effect of lipophilia/aqueous solubility on etiolated wheat coleoptiles elongation has been carried out with 34 guaianolides having different numbers of hydroxyl groups and ester side chains of variable length and structure: linear, branched, aromatic, and unsaturated. Compounds have been tested in a range of concentrations between 10 and 1000 microM. Data show a strong influence of lipophilia, expressed as logP values.

SAR studies of sesquiterpene lactones as Orobanche cumana seed germination stimulants.

Studies of the structure-activity relationship (SAR) directed to evaluate the effect of several sesquiterpene lactones (SL) as germination stimulants of three Orobanche spp. (O. cumana, O.