Classes of plant defense compound

Simple phenolics Phloroglucinol, gentisic acid, vanillin, caffeic acid, ferulic acid 

Complex phenolics Coumarins, phenolic quinones, lignins, flavonoids, stilbenes, hydrolyzable tannins, condensed (or catechin) tannins, phenolic lipids 

Alkaloids Nicotine, guinine, morphine, colchicine, strychnine 

Saponins Mustard oils Steroidal saponins, triterpene saponins 

Non-protein amino acids Phytohemagglutinins (lectins) Selenocystathionin, L-mimosine 

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Table 11.1 Classes of plant compound with antiherbivore defense functions...

How much a mammal eats of a given plant often depends on the levels of different classes of chemical constituent, notably nutrients and plant secondary metabolites. As in birds, it is not the plant defense compounds alone, but rather complex balances between nitrogen and carbohydrate contents, levels of defense compounds, and fiber that determine palatability. 

In this review, we examine the induced chemical defenses of P. abies, defenses whose levels increase following herbivore or pathogen attack. Induced defenses have attracted much attention in recent years because of their widespread occurrence in plants and their usefulness as subjects for study. Here, we cover the induction of several different classes of induced defenses in P. abies, including terpene-containing resins, phenolic compounds, and chitinases. Our focus is not only on their defensive roles, but also on how the levels of these compounds may be manipulated by biochemical and molecular methods while minimizing other phenotypic changes. Manipulation of defense compoimds in intact plants is a valuable approach to assessing their value to the plant. 

Flavonoids are the class of plant polyqthenols with a wide spectrum of biological activities. Flavonoids protect plants against different kinds of stress. They act as a UV-filter, function as a signal molecules, antimicrobial defensive compounds, etc. [8]. 

Extracts of plants have been used as insecticides by humans since before the time of the Romans. Some of these extracts have yielded compounds useful as sources (e.g., pyrethrins, rotenoids, alkaloids), others as models (e.g., pyrethrins, physostigmine) of commercial insecticides. Recent technological advances which facilitate the isolation and identification of the bioactive constituents of plants should ensure the continued usefulness of plant compounds in commercial insect control, both as sources and models of new insect control agents and also as components in host plant resistance mechanisms. The focus in this paper will be on several classes of compounds, including limonoids, chromenes, ellagitannins, and methyl ketones, which were found to be components of the natural defenses of both wild and cultivated plants and which may be useful in commercial insect control. 

Small molecule carboxylates are an important class of compounds that plants produce to attract pollinators,44 defend against herbivory,45 7 regulate the cell cycle,48,49 and induce defense responses.50 5 Often these compounds are esterified and volatilized. Plants utilize the emission of volatile esters as chemoattractants and signaling molecules. Classes of volatile compounds include the salicylates and jasmonates, which are ubiquitously distributed in the plant kingdom. Jasmonic acid, salicylic acid, and their methyl ester derivatives, are intimately involved in cell regulation and help control such developmental processes as seed germination, flower development, fruit development, and senescence.14,17,53... 

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. 

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