Labdanes

More than 500 labdanes predominantly isolated from higher plants are known to date They represent 8,11-10,15-cyelophytanes that contain the deealin bicyele as a eore strueture, whieh also defines the usually accepted ring numbering. 

The name labdane stems from Cistus labdaniferus (C sXacQzs) growing in Mediterranean countries (southern parts of France and Italy, Spain). This shrub and other Cistus species excrete the dark brown labdanum resin this has a pleasant smell like ambergris and contains not only a-pinene but also labdan-8a,15-diol and 8p-hydroxylabdan-15-oic acid. 

Constituents of Pinaceae and Cupressaceae include 8,5,18-labdanetrioI, (-)-labda-nolic acid and (+)-6-oxocativic acid. Numerous derivatives have been found in conifers such as pine (Pinus), fir (Abies), larch (Larix) and juniper (Juniperus). Selected examples are (+)-12,15-epoxy-8(17),12,14-labdatriene (pumiloxide) from Pinus pumila, (-l-)-12,14-labdadien-8-ol (abienol) from Pinus strobus and various Abies species, (+)-ll,13-labdadien-8-ol (neoabienol) from Abies sibirica, (-)-13(16),14-labdadien-8-ol (isoabienol), (+)-8(17)-labdene-15,18-dioic acid from the needles of Pinus silvestris (Pinaceae) and 14,15-dihydroxy-8(17),13(16)-labdadien-19-oic acid fxora Juniperus communis (Cupressaceae). 

A combination of spectroscopic evidence and chemical degradation has been used to determine the structure and absolute configuration of a new labdane-type diterpene, trans-(5 R, 7iS, 85,9S, 105)-labda-12,14-dien-7,8-diol (516) isolated from Porella species (62). The positions and configurations of the tertiary and the secondary hydroxyl groups were established by formation of (521) from (516), the facile dehydration of (521) to give (522), and by the appearance of the H-7 signal in the H-NMR spectrum as a (W = l Hz). The negative CD curve of (522) further 

Recently some highly oxygenated labdane-type diterpenes (517—520) have been isolated from Ptychanthus species (Jungermanniales). The structure proposals rest on H-NMR and C-NMR spectral analysis (321, 322). 

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With very few exceptions, the pine resin acids belong to four basic skeletal classes abietane, pimarane, isopimarane, and labdane (Fig. 7). The acids of the abietane, pimarane and isopimarane series have a isopropyl or methyl/ethyl group in the carbon-13 position and a single carboxyl group in the carbon-18 position, and differ only in the number and location of the carbon-carbon double bonds (the most common have two carbon-carbon double bonds). The acids of labdane series are less common and contain one carboxyl group in the carbon-19 position. 

Heterocycles in synthesis of drimane sesquiterpenoids from labdane diterpenoids 97IZV896. 

Labdan-gummi, -harz, n. labdanum, ladanum. Labdriise,/. peptic gland, laben, c.f. curdle with rennet refresh. Laberdan, m. salted codfish. 

Demetzos, C. and Perdetzoglou, D. 2002. Diurnal and seasonal variation of the essential oil labdanes and clerodanes from Cistus monspeliensis L. leaves. Biochem. Syst. Ecol. 30 189-203. 

Pang L, de las Heras B, Hoult JR. A novel diterpenoid labdane from Sideritis javalam-brensis inhibits eicosanoid generation from stimulated macrophages but enhances arachidonate release. Biochem Pharmacol 1996 51 863-868. 

The plant is attracting a great deal of interest on account of its ability to elaborate labdane diterpenes vitexilactone, 6-acetoxy-9 hydroxy 13(14)-labden-16,15-olide, rotundifuran,... 

Li WX, Cui CB, Cai B, Yao XS. Labdane-type diterpenes as new cell cycle inhibitors and apoptosis inducers from Vitex trifolia L. J Asian Nat Prod Res 2005 7 95-105. 

Of the Cupressaceae family, sandarac (from Tetraclinis articulata) has frequently been used as a paint varnish. It contains labdane compounds that account for the polymeric fraction of the resin (about 70%) [31]. The main monomeric diterpenoid present is sandaracopimaric acid, together with smaller amounts of 12-acetoxysandaracopimaric acid. Phenols, including totarol, are also present [31]. 

Labdanum resin (from the Cistaceae family) contains diterpenoid compounds with a labdane-type structure, namely laurifolic, cistenolic and labdanolic acids [100 103]. 

J. de Pascual Teresa, J.G. Urones, I.S. Marcos, F. Bermejo, P. Basabe, A rearranged labdane salmantic acid from Cistus laurifolius, Phytochemistry, 22, 2783 2785 (1983). 

M.T. Calabuig, M. Cortes, C.G. Francisco, R. Hernandez, E. Suarez, Labdane diterpenes from Cistus symphytifolius, Phytochemistry, 20, 2255 2258 (1981). 

Characteristic markers of Venice turpentine are larixol and larixyl acetate, but in many cases they may remain undetected, as larixyl acetate hydrolyses and the methylation of hydroxyl groups is not as effective as for carboxylic acids. On-line derivatization with tetramethylammonium hydroxide (TMAH) is, for instance, scarcely effective on hydroxyl groups and involves a number of secondary reactions (isomerization, dehydration and cleavage of hydrolysable bonds) due to the strong alkalinity of the TMAH solution. When the experimental conditions are such that THM of labdanes occurs larixol and larixyl acetate are detected as a single peak since in the derivatization process larixyl acetate is hydrolysed to larixol [29]. 

In Pinaceae resins, for instance, fully trimethylsilylated derivatives of 7-hydroxy-DHA, 15-hydroxy-DHA and 15-hydroxy-7-oxo-DHA have been identified, as well as all the other abietadiene and pimaranediene acids present in these resins. The derivatization was ineffective on some labdane alcohols such as larixyl acetate, a marker compound for Venice turpentine, but in general labdane compounds have been identified in their trimethylsilylated form. Labdane acids, such as communic, agathic, agathalic, agatholic and acetoxy agatholic acids, that are among the most important constituents of sandarac... 

Ditellurides, 24 422 Diterpene glycosides, 24 239 Diterpenoid acids, 24 552 Diterpenoids, 24 550-555 labdane family of, 24 573 Di -ferf-alkyl peroxides, 23 439-441 as free-radical initiators, 14 288... 

Laballenic acid, physical properties, 5 33t Labdane family, 24 573 Labeled compounds... 

Figure 2.16 Three labdane resin acid compounds (a) isocupressic acid, (b) the acetyl derivative acetlisocupressic, and (c) the succinyl derivative succinylisocupressic, found in certain pine, juniper and cypress trees and which are abortifacient in late-term pregnant cattle.

Andrographolide, a labdane-diterpenoid lactone, is the principal bioactive chemical constituent of Andrographis paniculata (Brum. F.) Nees (family Acanthaceae) this prime constituent is mainly concentrated in leaves and can easily be isolated from the crude plant extracts as crystalline... 

The plant Stevia rebaudiana bertoni has been studied in depth because it was discovered that this plant is the source of six sweet-tasting diterpene glycosides. They are stevioside, rebaudiosides A, C, D, E and dulcoside A. (Table 1). These sweet diterpene glycosides, as well as a complex mixture of organic compounds of which more than a hundred compounds have been identified, are found mainly in the leaves of the plant. The leaves contain a complex mixture of labdane diterpenes, triterpenes, stigmasterol, tannins and volatile oils. There is an abundance of reviews and patents relating to these sweet diterpene glycosides. 

Cuticular diterpenes-duvanes and labdanes. Cutler have found that the cuticular diterpenes of green tobacco have both allelopathic and insect-deterrent effects (38). Present in the cuticle are duvane and/or labdane diterpenes (Figure 3) The levels of these specific cuticular components are believed to be responsible for the observed resistance of some types of tobacco to green peach aphids Myzus persicae (Sulzer), tobacco budworm Heliothis virescens (F.), and tobacco hornworm Manduca sexta (L.) (39). 

Figure 3. Cuticular Diterpenoids—Duvanes and Labdanes important in host-plant resistance to insects.

Solldago is a mostly North American genus of about 125 species. It belongs to the Asteraceae (Compositae), a family with a very distinctive chemistry (57, 58). The genus itself contains several different classes of secondary compounds including a number of diterpenes (59). During the 1960 s and 1970 s Anthonsen in Finland, and McCrindle and his coworkers in Canada, isolated about twenty-five different compounds from the roots of Solidago species, mainly clerodanes and labdanes. But in the last five years attention has turned to the aerial parts of the plant and compounds of several other classes of diterpenes, abietanes and kauranes, have been isolated (60-79) (Table II). 

Labd-8-en-13-one, 15-16-di-nor LfNT535 Labd-8-ene-7-13-dione, 14-15-di-nor Fl Labdan-13-one, 11-12-epoxy-8-hydroxy-14-15-di-nor, 11(S)-12(R) F1NT338... 

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