Defensive Secretions

Cubitene is a diterpene present in the defense secretion of a species of African termite What unusual feature charactenzes the joining of isoprene units in cubitene" ... 

Formic acid [64-18-6] (methanoic acid) is the first member of the homologous series of alkyl carboxyHc acids. It occurs naturally ia the defensive secretions of a number of insects, particularly of ants. Although the acid nature of the vapors above ants nests had been known since at least 1488, the pure acid was not isolated until 1671, when the British chemist John Ray described the isolation of the pure acid by distillation of ants (1). This remained the main preparative method for more than a century until a convenient laboratory method was discovered by Gay-Lussac (2). The preparation of formates using carbon monoxide was described by Berthelot in 1856. 

Terpenoid substances are of broad distribution and diverse function in insects. One set, elaborated by the mandibular glands of Acanthomyops claviger, acts both as a defensive secretion and as an alarm releaser. When fed Cu-labeled acetate or mevalonate, laboratory colonies of these ants produce radioactive citronellal and citral, providing unambiguous evidence for de novo synthesis of these terpenes by the ant. The incorporations of these precursors implicate the mevalonic acid pathway as the likely biosynthetic route. 

Kara, M.R. et al., A comparative analysis of the chemical nature of defensive secretions of Gonyleptidae (Arachnida, Opihones, Laniatores), Biochem. Syst. Ecol, 33, 1210, 2005. 

While arthropod defensive secretions often rely for their effect on well-known aliphatic acids, aldehydes, phenols, and quinones, there are many cases in which compounds capable of whetting the appetite of any natural products chemist are utilized. For example, steroids play a... 

There is also another defensive secretion that sea hares release less readily than ink. This is a milky white liquid called opaline, so viscous that it can be stretched out through the air into a long string. For sea hares, opaline is what is known as a defining characteristic, because all sea hares emit opaline whereas no other species are known to do so. In spite of its defining role, opaline remains poorly understood. It contains proteins and perhaps components derived from the animals diet the evidence here is in dispute. A sea hare releases opaline less readily than ink but seems to do so as a second response to serious predatory assaults. When touched by a sea anemone s tentacles, a sea hare discharges a shot of opaline, which causes the anemone s tentacles to contract. No one yet understands how opaline deters predators or what chemicals are responsible for its activity. 

Adults of some species also produce 4-oxo-( )-2-alkenals. Other types of simple compounds that have been found in the defensive secretions of true bugs include common terpenoids such as a- and (3-pinenes, limonene, linalool, and Z, -oc-farnesene, and simple aromatic compounds such as benzyl alcohol, ben-zaldehyde,p-hydroxybenzaldehyde, methyl p-hydroxybenzoate,phenylethanol, and guaicol. In general, although a number of species may share particular components, each species does appear to produce its own particular blend. In at least one species, the blend of defensive compounds is reported to vary with season and/or diet [36]. 

Alarm pheromones, consisting of typical components of bug defensive secretions (e.g., simple aldehydes and esters), have been reported for Leptoglos-sus zonatus [122] and Leptocorisa oratorius [123]. 

Fig. 4 Evolution of solvents and solvent-mixtures in the defensive secretion of Oxytelinae (Staphylinidae) beetles. The secretions of all worldwide investigated species are saturated with the toxic compound p-toluquinone (left). The topical irritancy of the mixtures is continuously increased from primitive to advanced taxa. The cladogram on the left side includes the most important primitive (Deleaster Coprophilus, Syntomium) and several advanced genera [117,122]...

Apart from the primitive Deinopsini and Gymnusini, adult Aleocharinae show impaired tergal glands situated between tergites 6 and 7 [ 127]. Up to now, chemical data of the topically active defensive secretions are available from... 

In Australian tenebrionid beetles, defensive compounds and their patterns seem to be of only low chemotaxonomic value. However, the aforementioned aromatic compounds are restricted to the genus Tribolium. Abdominal defensive compounds were used as chemosystematic characters in order to construct a phylogenetic tree for the genus Tribolium [330]. The defensive secretion of adults of Tenebrio molitor was shown to contain toluquinone 7 and m-cresol 89 [333]. The quantification of benzoquinones in single individuals of Tribolium castaneum at different days after adult eclosion indicates that the amount of toxic quinone only shows a maximum subsequent to cuticle sclerotization. Obviously, there is a need for an adequate cuticular barrier for self-protection from these defensive compounds [334]. 

If many unpalatable Lepidoptera obtain their defensive quality by sequestering plant-derived substances, various caterpillars fortify their bodies with spines and hairs containing various toxins [167]. Defensive secretions in specialized exocrine glands were also reported [150-152]. 

Biogenic amines and phenolic compounds were also characterized from the defensive secretion of other saturniid caterpillars such as Saturnia pavonia, S. pyri, and Eupackardia calleta [169] and the chemical ecology of Saturniidae and Lymantriidae was recently reviewed by Demi and Dettner [170]. 

On the other hand, the defensive secretions of Sipyloidea sipylus and of Megacrania tsudai, two phasmid insects originating from Asia, contain volatile compounds, and, in both cases, the whole secretion has a repellent activity [180,181]. 

Finally, the antifungal properties of a-pinene and limonene, two monoter-penes frequently found in the defensive secretion of Nasutitermes termites, was studied. In vitro assays showed that these molecules reduce spore germination of the fungus Metarhizium anisopliae through direct and indirect (vapor) contact [225]. Moreover, some diterpenes isolated from these insects have also an antibiotic activity on Bacillus subtilis, Staphylococcus aureus, and Enterococcus faecalis [226]. 

Weatherston J, Percy JE (1970) Arthropod defensive secretions. In Beroza M (ed) Chemicals controlling insect behavior. Academic Press, New York, p 95... 

Only a few compounds or mixtures of compounds have been shown beyond doubt to be mammalian pheromones. This is the main reason why the subject matter of this chapter is not restricted to pheromones and why exocrine secretions and other mammalian excretions in general will be discussed as possible sources of pheromones, even though their role in the chemical communication of the species under discussion has not yet been established. Feeding deterrents are not discussed. In general defensive secretions are also not discussed, but the anal sac secretions of the mustelids are included, because it is possible that these secretions could also fulfill a semiochemical role, in addition to being used for defense. 

Beetles - Doryphorina sp. and Defensive secretions of beeties Platyphora kollari Fungi - Clavulinopsis helvola... 

Among the traly obnoxious odors in nature are those associated with the defensive secretions of the skunk. As you might expect, these are sulfur compounds. The striped skunk accumulates a store of these and, when threatened, can eject them rather accurately in the direction of a potential predator within a range... 

Striped skunk defensive secretion contains a number of compounds but two are largely responsible for the odor tra 5 -2-buten-l-thiol and 3-methylbutane-l-thiol ... 

These are volatile compounds and do have rather dreadful smells. They also occur in skunk spray in the form of their acetate esters. These are much less volatile and so contribute less to the immediate odor. However, on contact with water, they are slowly converted to the free thiols, a reaction that accounts for the persistence of skunk odor for days or weeks. The chemical components of skunk defensive secretion vary somewhat from species to species but thiols play a prominent role in all cases. 

Of several related steroids in the defensive secretion of dytiscid beetles, deoxycorticosterone was most effective. It deterred simfish from feeding in 94% of the tests. Other steroids (pregnolones) that differed only by lacking a keto group at one carbon atom were either intermediate or not active at all (Gerhart etal., 1991). 

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