Antifeedants plant compounds

Escoubas, P. Lajide, L. Mizutani, J. Insecticidal and antifeedant activities of plant compounds potential leads for novel pesticides., American Chemical Scociety Washington, DC, 1994 Vol. 551, pp 162-71. 

Herbivores have evolved many offensive adaptations that counteract the defensive adaptations of plants, including antifeeding compounds (Rhoades, 1985). 

Diterpenoids have a wide range of biological activities. Their role in plant-insect interactions, both as antifeedants and growth inhibitors, is reviewed. Four ent-kauranes, kaur-16-en-19-oic acid, (-)-kauran-l > -ol, 15 t-hydroxy-(-)-kaur-16-en-19-oic acid, and 17-hydroxy-(-)-kaur-15-en-19-oic acid, have recently been isolated from the leaves of Solidago nemoralis.These compounds were found to have antifeedant activity against Trirhabda canadensis. 

Many triterpenes also have anti herbivore activity. In general, those which are highly oxygenated seem to be more active in this regard M). The role of cardiac glycosides, insects and their predators has been reviewed (91-94). A number of metabolically altered triterpenes from the Rutaceae, Meliaceae and Simaroubaceae are antifeedants. Extracts of neem tree seeds (Azadirachta indica. Meliaceae) were shown to be repellent to a number of insects when applied to various crop plants at low concentrations. The probable active compound is tetranortriter-pene, azadirachtin (9 ). This compound from the leaves and fruits... 

Furocoumarins such as isopimpinellin, bergapten, and kokusagin have antifeedant activity against Spodoptera litura (54). A number of similar compounds from umbelliferous plants have been demonstrated to be active antifeedants against Spodoptera litura. Periplaneta americana. Musca domestica. Blattela germani ca, and Stylopyga rhombifolia (98). 

Most acetylenic compounds in plants are derived from meta-bolically altered fatty acids. These often are active in plant-insect relationships. 8-cis-Dihydromatricaria acid is also found in the defensive secretion of the soldier beetle (Chaulioqnathus 1econtei) (125), and has subsequently been shown to have anti-feedant properties against Phidippus spp. (jumping spiders) (126). As previously mentioned matricaria ester has antifeedant properties to the pink bollworm, bollworm and tobacco budworm (115). 

Plant parts other than seeds have been less well studied and little attention has been placed on insecticidal modes of action of the defenses of the neotropical Meliaceae. Our study of the insect growth-reducing activity of 50 extracts of bark, leaf and wood of Central American Meliaceae showed the potent effect of these extracts against lepidopteran larvae and the potential for isolation of bioactive compounds from alarge number of these species. Extracts from the genera Trichilia and Cedrela (Xie etal., 1994 Ewete etal., 1996a Wheeler etal., 2001) show exceptional activity. Trichilia americana extracts have strong antifeedant activity to Spodoptera... 

The Brassica family produces a wide range of glucosinolate compounds, anionic glycosides produced by the plant as antifeedant protective chemicals. As significant amounts of these compounds are left in the oilseed rape meals that remain after oil extraction, there is currently interest in exploiting these materials as crop-protection products for control of soil-borne diseases (Palmieri, 2003). 

This volume treats pheromones (Chapters 4.01—4.06), defensive substances and toxins (Chapters 4.08—T. 10), antifeedants (Chapters 4.11-4.12), compounds employed in plant-plant and plant-microbe interactions (Chapter 4.13), plant-insect interactions (Chapter 4.14) and microbe-microbe interactions (Chapter 4.07). Hormones of plants (Chapter 4.02) and insects (Chapter 4.03) are also treated in this volume. A unique attempt in the present volume is to regard flavor and fragrance (Chapter 4.15) and taste (Chapter 4.16) as phenomena of human-environmental interactions or human chemical ecology. 

Plants have, in the two-and-a-half million years they have coexisted with arthropods, evolved their own defenses against pests that attack them. It is only logical that we should look to them for compounds and structures that will deter pests. The search for feeding deterrents, commonly called antifeedants, is currently a rich source of new compounds potentially useful against pests of agriculture, forestry, and horticulture. 

In spite of the many studies on isolation, activity, and synthesis of natural antifeedants, the number of compounds commercially available remains low, often due to their cost of isolation, availability of the plant source, or low persistence in field conditions. To overcome these drawbacks, much research is conducted on structure—activity relationships (SAR). The rationale behind these studies is to discover the correlation between biological activity and chemical structure and to draw from that optimum structures having both the activity, stability, and selectivity for maximum feeding deterrence.4 5 SAR are much used in drug design6 and have been applied to insecticides.7... 

Compounds that inhibit oligosaccharide digestion not only impair herbivore nutrition but can also act as antifeedants. A variety of plant-derived secondary metabolites inhibit glycosidases (Table 13.1). Numerous plant protein glycosidase inhibitors have been isolated and some of these have dual functions as both a-amylase and trypsin inhibitors (Table 13.2). 

Antifeedants have been Isolated which represent many broad classes of compounds (2). Since It Is widely accepted that tropical flora have built-in defense mechanisms (2) due to their constant exposure to attack by many types of biological organisms Including Insects, the plants chosen for this study were selected from the Amazon River basin of Peru and the southern portion of the United States (Mississippi). The ethanolic extracts of more than five hundred plants from Peru and Mississippi were evaluated for potency with a boll weevil antlfeedant bloassay. 

Tliis study describes the isolation and bioassay against insects of six compounds from the Peruvian plant Alchornea trlplinervia. The compounds anthranilic acid, cinnamic acid, and camphor showed significant inhibition of the growth of the tobacco budworm. Anthranilic acid, gentisic acid, senecioic acid, cinnamic acid, and cinnamaldehyde demonstrated low to moderate activity in the boll weevil antifeedant bioassay. Cinnamaldehyde, a constituent of the spice cinnamon, showed the highest level of inhibition to boll weevil feeding. 

While much work has been done by innumerable workers trying to extract, purify, and identify various components of plants known to be relatively free from attack by insects, most of these materials have fallen in the category of true repellents rather than antifeeding compounds, and none have shown promise for practical production and usage. 

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