Defensive Substances Research Articles

Toxicological and Chemical-Ecological Studies on Insect Control

The purposeful rational design of insect control chemicals was based on studies of the mechanism and selectivity of insecticide action and of the chemical basis of insect behavior. I. Toxicological studies on insecticides. Studies on structure-activity relationships of nicotinoids demonstrated that the active nicotinoids should resemble acetylcholine with respect to their conformation and electronic makeup. The mode of insecticidal action elucidated provided the basis for developing new nitrogen-containing insecticides. Investigations on the fate of rotenone in various biological and photodecomposition systems and synthesis of its transformation products, as well as all possible stereoisomers of rotenone, enabled the analysis of the essential feature necessary for exerting its toxic action. A stereostructure defined by a 6aβ, 12aβ-configuration and hydrophobicity were essential. Also elucidation of the metabolic pathways of natural and certain synthetic pyrethroids formed the basis for understanding selectivity, resistance mechanisms, synergism and, with information on photoconversion, provided the groundwork for developing photostable pyrethroids. Reexamination of carbamates led to the finding of N-propylcarbamates, whose action was negatively correlated with the development of resistance of the green rice leafhopper to N-methylcarbamates. Recognition of the mechanism of action which involves the interaction with altered acetylcholinesterase led to the development of new anti-resistance insecticides. Thorough examination of the activation and deactivation reactions of thiono- or thiolo-phosphorus insecticides indicated the involvement of phosphorus oxythionate or sulfoxide intermediates. Such intermediates explained various chemical and toxicological results, and provided clues for developing new organophosphorus insecticides. II. Chemical-ecological studies on insect behavior. Callosobruchus chinensis and C. maculates have developed a strategy to reduce competition among larvae and to maximally utilize the host bean, first by marking the beans with exudates from their bodies and then killing the excess eggs using the same substances at accumulated doses. For mating, C. chinensis was found to produce a pheromone which induced the male to extrude his genital organ and to copulate with the female. All these ecochemicals were identified and their use for controlling the bean weevil is being developed. Sitophilus zeamais infests corn, wheat and rice grains. Chemical factors which cause such olfactory responses were identified. Also, chemical factors which cause attraction of the cheese mite, Tyrophagus putrescentiae, to cheese and other dairy and fermented food products were identified. Some work has been done on the defence substances produced by several Japanese stink bugs, Carabus procerulus and Damaster blaptoides oxuroides, as well as the osmeterium secretion of the caterpillars of swallowtail butterflies, and the trail-following pheromone of a Japanese termite, Reticulitermes speratus.

Synthesis of (3-Furanyl) Methyl Derivative

Abstract 3-Methylfuran is an important building block of terpenoid compounds1) and some of these compounds are biologically active, for example as a defence substance of animal.2) Though many methods have been developed for the syntheses of 3-substituted furan derivatives,3) most of them lack the generality as a synthetic method of (3-furanyl) methyl derivative. Tannis has recently reported the construction of 3-substituted furan derivative by using 3-(lithiomethyl) furan or 3-(chloromagnesium methyl) furan, and demonstrated the generality of his method.4)

Self defensive substances in rice plant against rice blast disease

From the resistant variety of rice plant, Fukuyuki, were characterized five epoxy fatty acids (1–5), which inhibit strongly the germination and germ tube growth of rice blast fungus, ED 50 being 20–30 ppm.

Fatty Acid Components of the Defensive Substances in Acid-Secreting Carabid Beetles

Fatty Acid Components of the Defensive Substances in Acid-Secreting Carabid Beetles

Chemical defense and self-defense: Biochemical transformations of contact insecticides produced by soldier termites

Soldiers of the advanced genera of rhinotermitids (Isoptera: Rhinotermitidae) produce lipophilic contact insecticides formally derived from fatty acids. Each of these defense substances possesses a reactive electrophilic center (vinyl ketone, nitroalkene, or β-ketoaldehyde) responsible for toxicity. We describe the synthesis of radioactively-labelled defense secretions of two of these species and their use in studying the substrate-selective detoxication by worker termites. Preliminary studies on biosynthesis of defense secretions by termite soldiers are also discussed.

Field studies of the relationship between herbivore damage and tannin concentration in bracken (Pteridium aquilinum Kuhn).

The acceptance of secondary plant metabolites as herbivore deterrents rests primarily on their deleterious effects on herbivores. Efforts to demonstrate differential fitness in natural plant populations with varying concentrations of tannin have failed, since coevolved plant predators may physiologically or behaviorally circumvent the defense, which results in apparently equal amounts of damage to defended and undefended individuals. In this study, two approaches were used to overcome this difficulty. 1) Theoretically, more energy should be allocated to the defense of parts which contribute more heavily to the plant's fitness. Bracken fern clones produce fronds throughout the growing season. Fronds which are produced early should be more heavily defended than late-emerging fronds which will return less photosynthate per unit cost of production. The results of this study do not support this prediction; it appears that the production of tannin is more closely linked to environmental factors such as water stress than to date of frond emergence. Fronds which emerged in August contained as much tannin as fronds which emerged in May. 2) By recording the temporal occurrence of herbivore damage in bracken ferns, it was found that in fronds which escaped attack until after reaching maturity there was a significant negative correlation between tannin concentration in the frond and the amount of damage experienced. This result supports the generally accepted assumption that herbivory has been a selective force in the evolution of tannin as a defensive substance.

Defenses of Nasutitermes Termites (Isoptera, Termitidae) Against Tamandua Anteaters (Edentata, Myrmecophagidae)

When carton nests or covered trails of Nasutitermes termites were breached experimentally, nasute soldiers were recruited rapidly to the break, while workers retreated into the nest or trail. Nasutes mobilized both in larger numbers and more rapidly to breaks in nests than at sites away from the nest. Nasutitermes formed an important part of the diets of two species of Tamandua anteaters. Anteaters, however, ignored or actively rejected most nests of Nasutitermes that they encountered, and fed primarily at concentrations of Nasutitermes in logs, branches, and covered trails away from the nest. Feeding at carton nests occurred mainly when these nests contained winged reproductives and nymphs or ants living in association with the termites. Feeding on Nasutitermes was often accompanied by grooming behavior. A captive T. mexicana rejected recently killed nasute soldiers while accepting both workers and reproductives of the same species. We suggest that the nasute soldiers are an effective defense against predation by anteaters on the nest and speculate on the role of mammalian termite-eaters in maintaining the Nasutitermes defense system. AMONG THE MOST SPECIALIZED of termite defensive behaviors are the chemical defenses of the Nasutitermitinae (Termitidae). For a recent review of termite defense mechanisms, see Deligne et al. (in press). The nasute soldiers of Nasutitermes squirt a defensive secretion through the long, pointed rostrum (Ernst 1959). This sticky, strong-smelling secretion is produced in the cephalic gland which occupies almost the entire head capsule (Noirot 1969). Most nasute soldiers lack mandibles and appear to function solely in colony defense. The defensive secretions of several species have been analyzed chemically and contain the volatile terpenoid compounds a-pinene, ,3-pinene, limonene and others, as well as a high molecular weight non-volatile component (Moore 1964, 1969; Vrkoc et al. 1973; Prestwich 1975, 1977). The defensive behaviors of Nasutitermes and other Nasutitermitinae were first described at the turn of the century by Beaumont (1889-90) and Andrews (1911), and analyzed in the laboratory by Ernst (1959), Moore (1964), Nutting et at. (1974), Stuart (1969, 1975), and Eisner et al. (1976). The cephalic gland secretion is both an alarm or alerting pheromone (Ernst 1959, Moore 1969, Stuart 1975, Eisner et al. 1976) and a defensive substance which immobilizes or slows small arthropod predators such as ants, to which it may also be toxic (Ernst 1959, Nutting et at. 1974, Eisner et at. 1976). The influence of nasute defensive secretions on vertebrate predators has been largely a matter of speculation (e.g., Eisner et al. 1976; 121: To what extent vertebrates might also be affected by these defenses remains to be

Irritant and Defense Substances of Higher Plants—A Chemical Herbarium

AbstractAll living organisms respond to stimulation, reacting more or less sensitively and more or less typically to a wide variety of energy forms such as light, heat, gravity, pressure (sound), electricity—and chemicals. A living organism responds to an irritation by releasing irritants which—as potential defense substances—are directed against the attacker or assist the organism endogenously in an intrinsic defense reaction. Often very small energy changes perceived by the plant are enough to induce a series of physiological processes ultimately manifested as a glandular reaction or even movement. The irritants involved in these processes act on membranes as defense substances in the presence of an attacker, or as endogenous factors in their own cellular environment. These chemically very diverse low‐molecular active principles have been found in many parts of plants and in many plant families. For this reason alone we could speak of a chemical herbarium, but the case is even stronger because, in this botanical documentation, not only the individual chemicals are considered in context but also whole sets of interacting substances, since it is only in these sets that optimal activity is found (just as one considers not only the parts of a plant but also the whole plant in botany).

Macrocyclic lactones as the defense substances of the termite genus [formula omitted

Soldier termites of three species of Armitermes (Isoptera: Nasutitermitinae) contain macrocyclic lactones possessing from 22 to 36 carbon atoms and novel C 24 and C 26 α- and β-hydroxy macrolides as the primary components of their cephalic secretions.

Biomimetic cyclization of hedycaryol derivatives. Unexpected cyclization of phenyl sulfides with methyl iodide

Four isomeric hedycaryol phenyl sulfides, when reacted with Mel, yielded eudesmol derivatives with different stereochemistry from that of the acid cyclization products of the corresponding hedycaryols. New stereoisomers of α- and β-eudesmols, β-dehydroparadisiol and a defensive substance of termite were synthesized. Nephthenol phenyl sulfide yielded a 14-membered tetraene.

Defensive substances from pygidial glands of water beetles

Abstract The pygidial gland secretions of water beetles of the dytiscidae have been shown to contain phenylpyruvic acid p -hydroxyphenylacetic acid, hydrocinnamic acid and 2-methyl-2-butenoic acid by a combination of several mass spectroscopical techniques, thin layer chromatography, UV spectometry and gas chromatography. The possible role of these compounds (auxin activity, antimicrobial properties, surfactant properties) and the co-occuring 3-indoleacetic

Defensive substances of opilionids

Two quinones (2,3-dimethyl-1,4-benzoquinone and 2,3,5-trimethyl-1,4-benzoquinone) and three phenols (2,3-dimethylphenol, 2-methyl-5-ethylphenol, and 2,3,4-trimethylphenol) were isolated from the defensive secretions of opilionids (Laniatores) from the Panama Canal Zone. The trimethylphenol was not previously reported as a natural product.

Chemical defense by termite soldiers

The chemistry of the defensive secretions of termite soldiers is reviewed. The structural variety of the chemical weapons, the uses of these substances in defense, and some potential biosynthetic interrelationships are discussed. Classification of the monoterpenes, sesquiterpenes, diterpenes, and various acetate-derived compounds according to termite subfamilies places the known defense substances in a phylogenetic perspective.

Phytoalexins, Chemical Defense Substances of Higher Plants?

AbstractPhytoalexins are defense substances with antimicrobial properties which are produced by plants after infection. They include various groups of natural substances (e.g. isoflavonoids, terpenoids, polyacetylenes and dihydrophenanthrenes). Induction of phytoalexin formation can be caused not only by living microorganisms but also by products of microbial origin (elicitors) or by stress treatment (cold, UV light). The elicitor from the mycelial walls of the fungus Phytophthora megasperma var. sojae (Pms) is a β‐1,3‐glucan with branches at C‐6. In some cases the basic features of the biosynthesis of the phytoalexins are known. The activity of the enzymes involved in phytoalexin biosynthesis is increased by the action of the elicitor on plant tissues. The ability of some microorganisms to chemically modify the phytoalexins may be related to their pathogenicity. The role of phytoalexins as defense substances is not yet fully clear.

Toxic Properties of the Chemical Defence Systems in the Competitive Ants Formica rufa and F. sanguinea

Formic acid and substances from Dufour's gland constitute the chemical defence system in F. rufa L. and F. sanguinea Latr. The secretion from Dufour's gland consists in F. rufa mainly of hendecane and tridecane and in F. sanguinea mainly of hendecane, decyl acetate, and dodecyl acetate. The hydrocarbons at least are toxic for the ants also in small amounts. More importantly, however, the hydrocarbons and the acetates act as wetting agents for formic acid, which alone is rather harmless. There are only minor differences between the hydrocarbons and the acetates as wetting agents for formic acid. The substances kill the ants by penetrating their tracheal system, thus easily reaching the vital organs. The hydrocarbons and the formic acid of F. rufa are more toxic for both species than the substances from F. sanguinea. F. sanguinea also seems to be more sensitive than F. rufa to the defence substances from both of the species. The reason may be its smaller size. Differences in the composition of the secretion of Dufor's gland in the two species do not seem to explain the superiority of F. sanguinea in nest competition with F. rufa observed in the field. This may be explained by higher aggressiveness in F. sanguinea.

Microdetermination of defensive substances of insects.

Microdetermination of defensive substances of insects.

Defensive substances of opilionids

The defensive secretions of 4 species of opilionids were analyzed.Leiobunum ventricosum andHadrobunus maculosus produce 4-methylheptan-3-one, whileL. calcar produces E-4,6-dimethyl-6-octen-3-one.L. longipes produces E-4,6-dimethyl-6-nonen-3-one, a new natural product.

ChemInform Abstract: DEFENSIVE SUBSTANCES OF COCCINELLA TRANSVERSOGUTTATA AND HIPPODAMIA CASEYI, LADYBUGS INDIGENOUS TO WESTERN CANADA

The defensive substances of two species of ladybug indigenous to western Canada have been isolated. The known compounds precoccinelline (1) and coccinelline (2) are present in Coccinella transversoguttata, and hippodamine (3) and convergine (4) in Hippodamia caseyi. From the latter insect we have also isolated two new alkaloids, a new base, N-oxide pair, which we have named hippocasine and hippocasine oxide. The structure of hippocasine oxide (8) was established by spectroscopic methods and confirmed by X-ray analysis of the hydrochloride (9d and Fig. 1).

ChemInform Abstract: A TOTAL SYNTHESIS OF MYRRHINE, (.+‐.)‐HIPPODAMINE, AND (.+‐.)‐CONVERGINE

AbstractDas aus 2,4,6‐Kollidin (I) erhältliche Acetal (II) wird in drei Schritten in das Bis‐äthylenacetal(III) übergeführt, aus dem bei Reduktion mit Natrium in Isoamylalkohol als Hauptprodukt das all‐cis‐Piperidin (IV) erhalten wird.

Host Defense Mechanisms in the Gastrointestinal Tract

In this review of host defense mechanisms in the gastrointestinal tract, I have attempted to update the current conception of basic host defenses. Nonimmunologic defenses such as indigenous intestinal flora, peristalsis, secretions, gastric barrier, and antibacterial substances (lysozymes, bile salts, and natural antibodies) were discussed with respect to their contribution in preventing the penetration of microorganisms, enterotoxins, and other antigens across the mucosal surface. The local immunologic system, including SIgA, cell-mediated immunity and other immunoglobulins were discussed. It was emphasized that the immune response at epithelial surfaces was independent from the systemic immune response and related to the antigenic stimulus at the epithelium. Several conditions, including prematurity, malnutrition, and primary immunodeficiencies, were reviewed in order to illustrate that altered host defenses may predispose to pathologic uptake of antigens from the gut and the development of clinical disease. Finally, it was suggested that an approach to the management of these conditions requires the passive replacement of defense substances by an oral route in order to maintain protection within the gastrointestinal lumen. The use of human colostrum/milk as a substitute was suggested.