Defensive compounds against

The presence of a series of alkylamines and amides (114—120, 125—129) in the gasterothorax characterizes the two ponerine ants, Mesoponera species (Table VIII), which contain 3-isopentyl-2,5-dimethylpyrazine (20h) as the major exocrine compound in their heads (Table III). The major amine is V-isoamyl-V-nonylamine (114). These compounds are perhaps utilized as defensive compounds against selected predators (41). 

Flavonoids are important secondary metabolites involved in pigmentation of flowers, disease resistance, and so on. Among the flavonoids, kaempferol (67), quercetin (68), and naringenin (69) are most often cited as allelochemicals. (zh)-Catechin was identified in the root exudates from spotted knapweed Centaurea maculosa) as the compound responsible for its invasive behavior.45 The plant uses (-)-catechin (70) as an allelochemical facilitating its invasion and (+)-catechin (71) as a defense compound against pathogens. 

Electrophilic drags are generally not welcome unless, of course, they are created deliberately to be electrophilic, as in the case of the DNA alkylating reagents which are used to treat cancer. Electrophilic compounds tend to react with biomolecules such as proteins and DNA. The main defensive compound against electrophilic compounds is the tripeptide glutathione. Figure 8.4f shows... 

Phytoalexins are low molecular weight compounds produced in plants as a defense mechanism against microorganisms. They do, however, exhibit toxicity to humans and other animals in addition to microbes (30). Coumarins, glycoalkaloids, isocoumarins, isoflavonoids, linear furanocoumarins, stilbenes, and terpenes aU. fall into the category of phytoalexins (31). Because phytoalexins are natural components of plants, and because their concentration may increase as a response to production and management stimuli, it is useful to recogni2e the possible effects of phytoalexins in the human diet. 

Cellular defense mechanisms against toxins (A multistep mechanism for elimination of toxic metabolites and xenobiotics. It involves various transport, oxidation, and conjugation steps.) are usually divided into several steps as it is visualized on Fig. 3. Organic anion transporting proteins (OATPs) are responsible for the cellular uptake of endogenous compounds and... 

D. J. Reed, Cellular Defense Mechanisms against Reactive Metabolites , in Bioactivation of Foreign Compounds , Ed. M. W. Anders, Academic Press, Orlando, 1985, p. 71 -108. 

HowelF and Howell and Kremer found phenol accumulation assodated with the exposure of plants to ozone. Menser and Chaplin also reported an increase in the phenol content of tobacco leaves injured by ambient oxidants. Hoffman reported as much as an 80% increase in nicotine in leaves exposed to ozone at 0.24 ppm for 4 h. No increase was found after exposure to 0.06 or 0.12 ppm. Keen and Taylor found accumulation of several isoflavonoid compounds in soybean (Harosay 63) exposed to ozone. The presence of these compounds suggests a defense mechanism against ozone that is similar to that for disease resistance. 

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