Iridoid Glycosides

About: Iridoid Glycosides is a research topic. Over the lifetime, 769 publications have been published within this topic receiving 15509 citations.

Iridoids. A review.

Abstract: Tre review presents a glossary of the iridoid glycosides, secoiridoids, bis-iridoids, and non-glycosidic iridoids. The following information is present for each compound, when available: structural formula, molecular formula, molecular weight, mp and [alpha]D values, uv, ir, 1H-nmr, 13C-nmr, and ms data, as well as mp and [alpha]D values for the correspondent acetate derivative. The natural source, the family and generic name, is given as well as the reference. A cross index and molecular weight tables are presented.

Effects of plant age, genotype, and herbivory on plantago performance and chemistry'

Abstract: Plant performance and chemistry may vary due to a variety of factors, such as plant genotype, environmental conditions, presence of herbivores, timing of herbivory, and species of herbivore. The relative importance of these factors, and how the plants respond to them, may affect the dynamics of the plant population, as well as the insect herbivores feeding on those plants. To understand the relative importance of some of these factors on plant performance and chemistry, we used Plantago lanceolata L. (Plantagina- ceae). In an experimental garden at Binghamton, New York, we examined the effects of plant age, plant genotype, and herbivory by generalist or specialist caterpillars on P. lan- ceolata. There were two parts to this experiment. In the first, we examined variation in nutritional quality (nitrogen) and defensive chemistry (the iridoid glycosides aucubin and catalpol) as a consequence of plant age, plant genotype, and leaf age class. We compared these parameters for a set of four pairs of plants of each of five genotypes that were not exposed to herbivores, and were harvested in early July (control-start plants) with another set harvested 6 wk later in mid-August (control-end plants). The older plants harvested in August (control-end plants) had concentrations of aucubin, catalpol, total iridoid glycosides, and nitrogen approximately one-half that of plants harvested 6 wk earlier. Leaf age affected all of these variables, and plant genotype influenced the iridoid glycoside variables but not the nitrogen concentration. Overall, leaf age explained twice as much of the variation in iridoid glycosides as did plant age, which accounted for twice as much variation as did plant genotype. The second part of the experiment compared the effects of herbivory, genotype, and leaf age on plant performance (leaf biomass, scape (flower stalk) biomass, and total biomass) and chemistry (nitrogen, protein, and iridoid glycoside concentration). We compared these measures for a set of four pairs of replicate plants of each of five genotypes, exposed to one of three herbivory treatments: no herbivory, herbivory by specialist caterpillars, and herbivory by generalist caterpillars. The results of this experiment showed that herbivory had little effect on plant performance, and there was no difference due to herbivory by the specialist Junonia coenia Hibner (Nymphalidae), compared to the generalist Spilosoma congrua Wlk. (Arctiidae). However, plant chemistry was significantly affected by herbivory. Herbivory by both caterpillar species induced iridoid glycosides and resulted in an increased concentration of catalpol and an increase in the proportion of catalpol relative to total iridoid glycosides in those plants exposed to herbivores compared to controls. In addition, plants exposed to specialist caterpillars had higher concentrations of catalpol and a higher proportion of total iridoids that was catalpol than those exposed to generalist caterpillars. Overall, in this experiment, leaf age explained three times as much of the variation in iridoid glycosides as did plant genotype and herbivory. The results of the two parts of this experiment show that iridoid glycoside concentration in P. lanceolata leaves decreases over time, and that exposure to herbivores induces increased concentrations of iridoid glycosides.

Naturally Occurring Iridoids. A Review, Part 1

Abstract: A compilation of new naturally occurring iridoid glycosides, iridoid aglycones, iridoid derivatives and bis-iridoids reported during 1994-2005 is provided with available physical and spectral data: mp, [alpha]D, UV, IR, 1H- and 13C-NMR as well as natural source with family and references. 418 compounds with 202 references are cited.

Enzymatic activation of oleuropein: A protein crosslinker used as a chemical defense in the privet tree

Abstract: Leaves of the privet tree, Ligustrum obtusifolium, contain a large amount of oleuropein, a phenolic secoiridoid glycoside, which is stably kept in a compartment separate from activating enzymes. When the leaf tissue is destroyed by herbivores, enzymes localized in organelles start to activate oleuropein into a very strong protein denaturant that has protein-crosslinking and lysine-decreasing activities. These activities are stronger than ever reported from plant systems and have adverse effects against herbivores by decreasing the nutritive value of dietary protein completely. We report here that strong oleuropein-specific β-glucosidase in organelles activates oleuropein by converting the secoiridoid glucoside moiety of oleuropein into a glutaraldehyde-like structure, which is also an α,β-unsaturated aldehyde. Oleuropein activated by β-glucosidase had very strong protein-denaturing, protein-crosslinking, and lysine-alkylating activities that are very similar to, but stronger than, those of glutaraldehyde. Aucubin, another iridoid glycoside, had similar activities after β-glucosidase treatment. We also detected polyphenol oxidase activity in organelles that activate the dihydroxyphenolic moiety to have protein-crosslinking activities. These data suggest that the privet tree has developed an effective defense mechanism with oleuropein, a unique multivalent alkylator ideal as a protein-crosslinker. Our results that iridoid glycosides are precursors of alkylators may elucidate the chemical bases that underlie various bioactivities and ecological roles of iridoid glycosides.

Response of generalist and specialist insects to qualitative allelochemical variation.

Abstract: We examined the effects of a set of four biosynthetically related iridoid glycosides, aucubin, catalpol, loganin, and asperuloside, on larvae of a generalist,Lymantria dispar (Lymantriidae), the gypsy moth, and an adapted specialist, the buckeye,Junonia coenia (Nymphalidae). In general,L. dispar grew and survived significantly less well on artificial diets containing iridoid glycoside, compared to a control diet without iridoid glycosides. In choice tests, previous exposure to a diet containing iridoid glycosides caused larvae subsequently to prefer iridoid glycoside-containing diets even though they were detrimental to growth and survival. In contrast,J coenia larvae grew and survived better on diets with aucubin and catalpol, the two iridoid glycosides found in the host plantPlantago lanceolata (Plantaginaceae), than on diets with no iridoid glycoside or with loganin and asperuloside. The results of choice tests of diets with and without iridoid glycosides and between diets with different iridoid glycosides reflected these differences as well. These results are discussed in terms of (1) differences between generalists and specialists in their response to qualitative variation in plant allelochemical content, (2) the induction of feeding preferences, and (3) the evolution of qualitative allelochemical variation as a plant defense.