Tri terpenes

The main compounds detected by headspace SPME in six olibanum samples are given in Table 10.3. Qualitative results obtained by headspace SPME were identical to those obtained by classical extraction with dichloromethane, except for the tri terpenes. 

Sterols 280) occur widely in the animal kingdom phytosterols found in most groups of plants. Triter-penes are rare in animals but occur in many groups of plants. Pentacyclic tri-terpenes are in abundance and considerable variety in the higher land plants 65). 

Pokeweed contains phytolaccatoxin and related tri-terpenes. All plant parts are poisonous, especially the roots. Uncooked berries have been known to poison children. Toxic exposures have occurred from eating the uncooked leaves in salads or when the root is mistaken for horseradish, parsnip, or ginseng. Effects appear 30 min to 6h after exposure. Symptoms include nausea, abdominal cramps, profuse sweating, and foamy diarrhea. Other effects include oral burning, a bitter taste in the mouth, dyspnea, weakness, tremors, and seizures. One case of Mobitz Type I heart block has been reported after ingesting poke-weed, but is believed to be secondary to parasympathetic effects from prolonged vomiting. Symptoms may last up to 48 h. As few as 10 berries can result in toxic effects. Dermal exposures result in irritation, pain, and the sensation of heat. 

Ehrhardt, J.D., L. Hirth, and G. Ourisson Etude des tri-terpenes tetracycliques des feuiUes de tabac. Presence de cycloartenol absence de lanosterol [Study of the tetracyclic triterpenes in tobacco leaf. Presence of cycloartenol absence of lanosterol] Compt. Rendu Acad. Sci. 260 (1965) 5931-5934. 

Occurrence In the outer parts of birch bark Betula alba, Betulaceae) in amounts of up to 24% dry weight and in other barks together with saponins and sesquiterpene alcohols such as betulenol. B. is a triterpene alcohol with the lupane skeleton (cf. figure under tri-terpenes) and was one of the first natural products to be investigated (first mentioned in 1788 ). 

CucurbHacins. Large group (>40) of tetracyclic tri-terpenes, mostly occurring in glycosidic form (exceptions C. A, C. C, and C. F) as poisonous bitter substances in cucumber and pumpkin plants (Cucurbitaceae) as well as in some craciferous plants (Brassicaceae) they have also been isolated from an agaric ( hebevino-... 

C30H48O3, Mr 456.71, mp. 306-308°C, [a]j, -i79.5° (CHCI3), insoluble in water, soluble in ether. The tri-terpene O. occurs in the free and acetylated forms as well as in many glycosides of various plants such as mistletoe, clove, sugar beet, olive leaves, beeches, etc. O. has the oleanane skeleton. 

QuassMoids). A group of structurally complex tri-terpenes with various tetra- and pentacyclic C -, C -, C20-, and C25-skeleton. The C2o picra ane system is the most widely distributed. Q. occur principally in the wood of the tree Quassia amara indigenous to Brazil and Surinam as well as the Caribbean Picrasma ex-celsa (Simaroubaceae). They have antifeedant effects on insects and taste very bitter. The most important representative of the Q. is quassia (2,12-dimethoxy-picrasa-2,12-diene-1,11,16-trione, nigakilactone D) C22H28O6, Mr 388.46, mp. 221-222 °C, [aJo +34.5° (CHCI3) - a partially hydrogenated phenanthiene derivative. 

Composition S. balsam consists of up to ca. 50% tri-terpene acids, and more than 45% of cinnamyl cinna-mate (see cinnamic acid) and 3-phenylpropyl cinna-mate (a) (CigHigOj, Mr 266.34), together with small amounts of more volatile compounds such as cinna-myl alcohol and hydrocinnamyl alcohol. The typical odor notes of S. are determined mainly by the trace content of styrene (b) (CgH, Mr 104.15). 

C. is biosynthesized from acetyl-CoA via the tri-terpene lanosterol (see Steroids, Figs. 7 8) and zymosterol. In turn, it is a key intermediate in the biosynthesis of many other steroids, including steroid hormones, steroid sapogenins and steroid alkaloids. 

Ursolic acid a simple unsaturated pentacylic tri-terpene carboxylic acid, M, 456.71, m.p. 292°C, [d o + T2° (CHCI3). U.a. is a structural derivative of a-Amyrin in which the 28-methyl group is replaced by a carboxyl group (see Amyrin). It occurs widely in plants as the free acid, esterified, or as the aglycon of triterpene saponins (see Saponins), e.g. in the wax layer of apples pears and cherries in the skin of bilberries and cranberries, and in the leaves of many members of the Rosaceae Oieoceae and Labiatae. 

Chaturvedula VS, Gao Z, Jones SH, Feng X, Hecht SM, Kingston DG (2004) A new ursane tri-terpene from Monochaetum vulcanicum that inhibits DNA polymerase p lyase. J Nat Prod... 

The multiples of isoprene units in a terpene serve to classify it Cio, monoterpenes C15, sesquiterpenes C20, diterpenes C30, tri-terpenes to which the steroids are closely related C25, sesterpenes. It is a curious thing to note that the isoprene rule, sound and powerfully useful not least for structure elucidation, has unnatural foundations. Isoprene (4.1) is not a naturally occurring compound. Instead the clay from which the terpenes are so orderly fashioned is isopentenyl pyrophosphate (4.14) and dimethylallyl pyrophosphate (4.15). The latter is seen in many natural compounds, e.g. (4.11) as a prenyl ... 

It turns out that they are chemically related to each other, as you can imagine from the chemical structures shown in Fig. 12.1. They are called terpenes and terpenoids. They can be regarded as derivatives from a five-carbon compound called isoprene (2-methyl butadiene). Two isoprene molecules combine to form mono-terpene (ten-carbon compound). The fragrant oils mentioned above are all the derivatives of mono-terpene. Terpenes are derived from a common metabolic intermediate of glucose, acetyl-CoA (coenzyme A). By the way, a tri-terpene (which three terpene molecules combine to form) called squalene leads to the formation of steroids, and if you connect a large number of isoprene in a linear fashion, you will get natural rubber (Chap. 5). 

The biosynthesis of the steroid alkaloids takes the usual paths of tri-terpene synthesis, i.e. via farnesyl pyrophosphate, squalene, and lanosterol or cycloartenol. The nitrogen probably comes from ammonia or ammonium compounds. 

Because they come from prokaryotes or eukaryotes, the natural substances isolated from marine organisms are often characterized by the presence of chemical elements or structures that are seldom observed, or even unknown, in a terrestrial environment. This observation applies as much to the primary metabolites (sulfated polyholosides, nucleosides) as to the secondary metabolites (e.g., haloge-nous and nitrogenous terpenes, sterols and sulfated tri-terpenes, arsenic-containing sugars). 

The study of the biosynthesis of this pentacydic tri-terpene showed that it was formed from mevalonic add (Mallory et al., 1968), and thus from squalene, but without the intermediate epoxysqualene (Caspi et al., 1968 Caspi, Greig, and Zander, 1968 Caspi, 1980). The cydi-zation of squalene is not oxidative and the oxygen atom comes from water, not from the atmosphere - research having shown that the biosynthesis of tetrahymanol takes place in either aerobic or anaerobic conditions (Caspi et al., 1969 Zander and Caspi, 1969 Zander, Greig, and Caspi, 1970). 

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