Antifeedants mammals

Condensation of coumaric acid with malonic acid yields the basic chalcone and stilbane skeletons (see Fig. 3.6). Stilbenes are found in most vascular plants, where they exhibit fungicidal and to a lesser extent antibiotic properties. They function as both constitutive and inducible defense substances. Some stilbenes inhibit fungal spore germination and hyphal growth, whereas others are toxic to insects and parasitic nematodes (round-worms). They also possess antifeeding and nematicide properties in mammals. For example, resveratrol (a stilbene in red wine) suppresses tumor formation in mammals. 

Stilbenes (from the Greek stilbos, glistening, after shiny crystals), are two-ring structures of the C6-C2-C6 type examples are pinosylvin and pinosylvin methyl ether (Fig. 11.2). They play a role as antifeedants for mammals. 

Nagilactones as an antifeedant from Podocarpus tiagi for herbivorous mammals. Hayashi, Y. Kim, Y. Hayashi, Y. Chairul. BioscL Biotech. Biochem. 1992, 56, 1302-1303. 

Activity M., trichilins, and azadirachtanin have strong antifeedant effects on insects, they cause growth impairments in, e. g., caterpillars of the forest pest Spodoptera in mammals M. cause severe poisoning symptoms of vomiting, cardiac weakness, nervous disorders, or death. Lit Bioorg. Med. Chem. 4, 1355 (1996) . Nat. Prod. 61, 179 (1998) Heterocycles 36,725 (1993) 38,2407 (1994) Phytochemistry 41, 117 (1996). 

Q. is used in the food industry as a bitter principle, according to legal regulations brandies may contain up to 50 mg/L Q. as bitter component. Q. has a bitter taste even at a dilution of 1 60 000. In mammals Q. can effect a decrease in heart rate and, at higher concentrations, muscular convulsions and paralyses. The commercially available quassin is a mixture of quassin, neoquassin, isoquassin, and 18-hydroxy-quassin. Q. can be used as a substitute for emetine hydrochloride (see ipecac alkaloids). Some pentacyclic Q. have antiviral, antiparasitic, insecticidal, antifeedant, amoebicidic, and anti-inflammatory activities. 

C15H20O2. Mr 232.32, cryst., mp. 86.5-87.5°C, [a]o -25° (CHClj). A lactarane derivative with a pungent taste and mutagenic and antimicrobial activities from toadstools of the genera Lactarius (milk caps). Russula, and other Russulaceae like the isomeric isovel-leral V. is formed enzymatically from stearoylveluti-nal within a few seconds after injury of the fruit body. This is followed in fungi such as L vellereus by an enzymatic detoxification in which V. is reduced within a few minutes to vellerol (C,5H2202, Mr 234.34). Vel-leral and isovelleral have antifeedant effects on insects and mammals (opossum). 

The use of antifeedants has an added advantage over that of toxicants in that the insect consumes little if any of the plant, thus limiting damage. Pest control materials which are specific for insects and which affect metabolic pathways or anatomical structures (including cellular) which are unique to insects may possess less toxicity for mammals, and thus may be superior as pesticides. It has also been speculated that highly specific lipolytic and proteolytic enzymes will be found to control specific processes in insects, as they do in mammals thus they will be important targets for research. 

Neem-based products are considered broad-spectrum against most orders of insects. Although at high concentrations the azadirachtins can act as a toxic insecticide, in most applications allowed concentrations produce only antifeedant effects. The neem-based products are considered to be of low toxicity to mammals. 

---