GermacreneD

Aerial parts of N. sintenisii yielded 0.3% of a clear yellowish oil. Forty constituents (96.5% of the total oil) were identified. The main components were 4aP,7a,7aP-nepetalactone (23.4%), elemol (16.1%), E- -farnesene (9.5%), 1,8-cineole (8.2%), cw-sabinene hydrate (6.5%), P-bisabolene (4.2%), germacrene-D (3.5%), P-sesquiphellandrene (2.8%), P-bourbonene (1.5%) and a-epi-cadinol (1.3%). According to available data, Nepeta species can be divided into two groups of nepetalactone-containing and nepetalactone-free species. The results of this study indicate that the compositions of volatile oil of N. sintenisii are similar to the other Nepeta genus and this plant could be classified in the group which 4aP,7a,7aP-nepetalactone is the major component of their oils. 

It should be noted that the stereochemical aspects of the Cope rearrangement are widely used for synthesis of various natural products, e.g. of the elemene-type derivatives 493-496 starting from germacrene-type sesquiterpenes 492 having cyclodeca-1,5-diene structure with stable conformations (equation 186)244. 

Pentalenene synthase fi-om Streptomyces sp. was cloned and overexpressed in Escherichia coli getting pentalenene, a known sesquiterpene site-directed mutants yielded other known sesquiterpenes, A -protoilludene and germacrene A (Seemann 1999). 

Leaf oil p-pinene (14), sabinene (13), terpinen-4-ol (11), and sesquiterpene hydrocarbons, bicycloger-macrene (29), germacrene D (12)... 

Germacrene-D, a ten-membered-ring system with three double bonds acting as electron-rich centers, and pinenes and menthadiene oiXylopia aethiopica EO showed a significant ability to scavenge superoxide anion radical [176]. EOs with /f-caryophyllene as the major compound showed radical-scavenging activity [177]. 

Nine compounds from branches with leaves and green fruit from apple consistently elicited an antennal response in codling female moths (Cydia po-monella, Lepidoptera), including methyl salicylate, ( )-/3-farnesene, /3-caryo-phyllene, 4,8-dimethyl-f,3( )-7-nonatriene, (3Z)-hexenol, (Z, )-a-farnesene, ( , )-a-farnesene, linalool and germacrene D [378]. 

Female antennae detected small amounts of ( )- -farnesene, (Z, )-a-farne-sene, methyl salicylate and germacrene D, while other more abundant compounds, such as (3Z)-hexenyl acetate and ( )- -ocimene, gave no significant antennal response [378]. 

Sesquiterpenes recovered by solvent extraction were identified in pineapple fruit Ananas comosus Merr.) from Cote d Ivoire. The authors suggested that some of the sesquiterpenoids found were derived from germacrene precursors [6]. The same authors studied the identification of trace compounds with impact character in pineapple fruit Ananas comosus Merr.). Some potent compounds were an undecatriene, an undecatraene, and ethyl esters [5]. 

The chiral hydrocarbon germacrene D is a widely spread plant constituent and is considered to be an important intermediate in the biosynthesis of many sesquiterpenes. Schmidt et al. [19, 20] have shown that the plant Solidago canadensis generates both optical antipodes of this compound by enzymatic cyclisation of farnesyl diphosphate using two different enantiospecific synthases. As to be seen in Fig. 17.5, the enantiomeric ratio of germacrene D in Solidago canadensis can vary from individual to individual [21]. 

Fig. 17.5 Enantioselective analysis of germacrene D from the essential oil of different Solidago canadensis plants, using the enantio-MDGC-mass spectrometry (MS) technique [21]...

Schmidt CO, Bouwmeester HJ, Franke S, Konig WA (1999) Mechanisms of the biosynthesis of the sesquiterpene enantiomers (-t) and (-) germacrene D in Solidago canadensis. Chirality 11 353... 

Franssen et al. [24] pointed out an alternative method of production of nootkatone from valencene catalysed by (-i-)-germacrene A hydroxylase, an enzyme of the cytochrome P450 monooxygenase type that was isolated from chicory roots. In general, this enzyme appeared to accept a broad range of sesquiterpenes and hydroxylates exclusively at the side-chain s isopropenyl group. Valencene is an exception it was not hydroxylated at the side chain, but -nootkatol was formed in the first step (Scheme 22.5) it is not yet clear if the second step is enzyme-catalysed. 

Scheme 22.5 Production of nootkatone from valencene catalysed by (+)-germacrene A hydroxylase [81]...

One year later, Schalk [89] described a process for cloning sesquiterpene synthases from patchouli plants Pogostemon cablin) and the enzyme-catalysed terpenoid production. Various sesquiterpenes can be obtained by this method, for instance patchoulol and other germacrene-type sesquiterpenes. 

Kadsura japonica (L.) Dunal Nan Wu Wei Zi (Kadsura) (vine) Kadsuric acid, kadsurin, kadsurarin A, germacrene.33-227 Against hepatitis B. Relieve pain, a detoxicant, improve blood circulation, reheve arm and leg numb feelings. 

N.A. Hedera helix L. Tannins, hederin, aglycone, iodine, beta-elemone, elixen, hederacoside B, hederacoside C, germacrene B.100 An expectorant with antispasmodic and cardiac actions. 

Germacrene Kadsura japonica, Rhododendron dauricum, R. mucmnatum ... 

Fig. 2.4. Chromatographic profiles of volatiles emitted by four plant species at different time periods after an attack by Spodoptem littoralis larvae. The labeled peaks are 1, (Z)-3-hexenal 2, ( )-2-hexenal 3, (Z)-3-hexenol 4, (Z)-3-hexenyl acetate 5, linalool 6, ( )-4,8-dimethyl-1,3,7-nonatriene 7, indole 8, ( )-/ -caryophyllene 9, ( ,)-o -bergamotene 10, ( >/3-farnesene 11, ( , )-of-farnesene 12, nerolidol 13, ( , )-4,8,12-trimethyl-1,3,7,11-tridecatetraene 14, of-pinene 15, /3-pinene 16, -myrcene 17, D-limonene 18, ( )-/3-ocimene 19, -sesquiphellandrene 20, germacrene D. Two internal standards, -octane and nonyl acetate, are labeled with IS1 and IS2, respectively.

An important step toward the correct identification of the sex pheromone of P. americana was the identification of several phytochemicals, such as bomyl acetate and santalol, that stimulated courtship behavior in males (Bowers and Bodenstein, 1971 see p. 196). Some years later, Tahara etal. (1975) and Kitamuta et al. (1976) reported that germacrene-D, extracted from composite plant species, stimulated sexual behavior in males of P. americana and the Japanese cockroach Periplaneta japonica Karny. Persoons etal. (1974, 1976) determined, on the basis... 

Another phytochemical that stimulated males and females differentially was T-cadinol, extracted from Solidago altissima L. It stimulated male and female antennae, but in comparison with germacrene-D, the responses were neither as sex specific nor as strong (Nishino et al., 1977c). 

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