Triterpenoids pentacyclic

Pentacyclic triterpenoids-lantadenes Lantana camara var. aculeate SiOj GF Petroleum + AeOEt + AcOH UV Purification, HPLC 43 ... 

The plant is known to produce norbisabolane diterpenes, including phyllanthusols A and B, which are both cytotoxic (36). From the bark, pentacyclic triterpenoids, phyl-lanthol, and olean-12en-3[3-ol (p-amyrin) have been isolated (37). Note lupane- and oleanane-type triterpenoids isolated from the bark of Phyllanthus flexuosus, such as olean-12-en-3 (3,15 a-diol, olean-12-en-3 [3,15 a,24-triol, lupeol, and betulin inhibited the enzymatic activity of topoisomerase II activity with IC50 values in the range of 10 to 39 p.M (38). 

Frankincense, also known as olibanum, is obtained from trees belonging to the genus Boswellia (Burseraceae family). It is one of the best-known ancient plant resins. The ancient Egyptians were the first to use it as incense in embalming practices and in the preparation of medicines, cosmetics and perfumes, and today it is still used therapeutically. It contains pentacyclic triterpenoids belonging to oleanane, ursane or lupane type molecules and in particular of a- and p-boswellic acids, and their O-acetates [104 111], 11 -Oxo-p-boswellic acid and its acetyl derivative, identified in several Boswellia species, are also diagnostic for frankincense [112]. 

Dammar resin was introduced into Europe in the nineteenth century, mainly as a paint varnish It is still used today since it has good optical properties and low acidity. It is derived from various species (the genus Hopea and Shorea of the Dipterocarpaceae family). It is characterised by tetracyclic triterpenoids of the dammarane series and contains minor amounts of pentacyclic triterpenoids of the series of olanane, ursane and hopane. It also contains a polymeric fraction named polycadinene or [S-resene. Dammar resin triterpenoids undergo oxidation with ageing, as described for the components of mastic resin. 

Betulin and lupeol, together with low amounts of lupenone, betulone and betulinic acid, are characteristic of birch bark [87,153 157]. All these compounds are pentacyclic triterpenoids with a lupane skeleton. In addition to triterpenoids, birch bark contains high amounts of a lipid material, called suberin [158]. 

The tetracyclic alcohol 179 is produced by the action of boron trifluoride etherate or tin(IV) chloride on the oxirane 178 (equation 85)95. A similar cyclization of the oxirane 180 yields DL-<5-amyrin (181) (equation 86)96. In the SnCLt-catalysed ring-closure of the tetraene 182 to the all-fraws-tetracycle 183 (equation 87) seven asymmetric centres are created, yet only two of sixty-four possible racemates are formed97. It has been proposed that multiple ring-closures of this kind form the basis of the biosynthesis of steroids and tetra-and pentacyclic triterpenoids, the Stork-Eschenmoser hypothesis 98,99. Such biomimetic polyene cyclizations, e.g. the formation of lanosterol from squalene (equation 88), have been reviewed69,70. 

VAN DER DEUDEN, R., THRELFALL, D.R., VERPOORTE, R WHITEHEAD, I.M., Regulation and enzymology of pentacyclic triterpenoid phytoalexin biosynthesis in cell suspension cultures of Tabemaemontana divaricata, Phytochemistry, 1989, 28, 2981-2988. 

Currently there is no experimentally determined three-dimensional structural information available for OSCs, although studies with a related enzyme, squa-lene-hopene cyclase (SC EC 5.4.99.7) have proved informative. SCs are involved in the direct cyclisation of squalene to pentacyclic triterpenoids known as hopanoids, which play an integral role in membrane structure in prokaryotes [ 51 ]. A number of SC genes have been cloned from bacteria [52 - 54]. The SC and OSC enzymes have related predicted amino acid sequences, and so should have similar spatial structures [55]. The crystal structure of recombinant SC from the Gram-positive bacterium Alicyclobacillus acidocaldarius has established that the enzyme is dimeric [55]. Each subunit consists of two a-a barrel domains that assemble to form a central hydrophobic cavity [55,56]. 

In Tabernaemontana divaricata treatment of plant cell suspension cultures with an elicitor cause inhibition of CS activity [24,25]. This response is accompanied by stimulation of activity of constitutive enzyme activities of the isoprenoid pathway leading to 2,3-oxidosqualene (squalene synthase and squalene oxidase), and induction of enzymes required for biosynthesis of pentacyclic triterpenoid phytoalexins (/lAS and aAS). Thus inhibition of the branchpoint enzyme CS results in increased flux through the triterpenoid pathway. 

Mahato, S. B, Kundu, A. P. (1994). C NMR spectra of pentacyclic triterpenoids- A compilation and some salient features. Phytochemistry, 37,1517-1575. 

The biomitetic polyene cyclizations pioneered by Johnson have culminated in stabilizing the cation404,405 and extension to the syntheses of pentacyclic triterpenoids in one step from an acyclic precursor )406-409. Johnson summarized his 50 years of research in a review410. 

The pentacyclic triterpenoid skeletons exemplified by lupeol, a-amyrin, and p-amyrin (Figure 5.60) are frequently encountered in the form of triterpenoid saponin structures. Saponins are... 

Diploptene pentacyclic triterpenoid (17fS(//),2l f (//)-hop-2l (29)-cnc) that has been found to be a useful diagenetic biomarker for bacterial activity. 

Boswelic acids are pentacyclic triterpenoids isolated from gum resin secreted by trees of Boswellia serrata Roxb. (Burseraceae). P-Boswelic acid... 

Two pentacyclic triterpenoids were isolated from Vitex negundo, an Indian medicinal plant of the Verbenaceae. They were identified as the known ursolic acid (201) and betulinic acid (202). After 48 h, the reduction in feeding by the larvae of the castor semilooper, Achoea janata, was 84.75% for 202 and 94.79% for 201, respectively, at a dose of 10 pgcm-2.91... 

Reviews have appeared on the palaeochemistry and biochemistry of hopanoids, the distribution of tetracyclic and pentacyclic triterpenoids, friedelin and associated triterpenoids, triterpenoid alcohols of seed-bearing plants (Sperma-tophyta), and the occurrence, biosynthesis, and metabolism of epoxides. ... 

Papers have appeared on the effect of different reagents on the course of the dehydration of the 3/3-hydroxy-group of acacic acid lactone and related pentacyclic triterpenoids,the ring A conformation of 2-methyl-3-hydroxy- and 2-methyl-3-oxo-derivatives of 19/3,28-epoxy-18a-oleananes, the use of lead... 

Two notable total syntheses of pentacyclic triterpenoids have been reported. In the synthesis of ( )-germanicol (115), the tricyclic ketone (116) was conceived as a general intermediate which embodies the features of rings A, B, and c of many triterpenoids. Conjugate addition of the benzyl Grignard reagent to the... 

The hydride shifts accompanying cyclization of 2,3-epoxysqualene (32) to lanosterol in yeast and to the pentacyclic triterpenoid S-amyrin in peas have been confirmed, thus supporting the previous proposals. 

Although they are known to be synthesized by a wide variety of cultured aerobic bacteria there does not appear to be any obligate requirement for oxygen in their biosynthesis. The biosynthesis and cyclization of squalene to a pentacyclic triterpenoid with a hopane skeleton does not seem to require oxygen and, therefore, hopanoid synthesis might also be possible in anaerobes. For instance, analysis of microbial mats at methane seeps under anoxic Black Sea water revealed the presence of C-depleted (8 C = -lS%c) hopanoids with an unusual stereochemistry. This isotopic depletion indicates in situ production and, therefore, suggests that anaerobes are responsible (Thiel et ai, 2003). 

The saponin structure is either of the steroidal (commonly tetracyclic triterpenoids) or pentacyclic triterpenoid type. Triterpenoid saponins are found, for example in Quillaia bark and in liquorice root. Quillaia B.P. is defined as the dried inner part of the bark of Quillaja saponaria and other species of Quillaja and is used as an emulsifying agent. Liquorice, the root of which also contains tiiterpenoid saponins, has long been used in pharmacy as a flavoring agent, demulcent, and mild expectorant. 

Hopanoids are pentacyclic triterpenoids that make up a class of essential membrane lipids [42,43,44]. They are believed to represent the most abundant natural products on earth. They occur widespread in Gram-negative and Gram-positive bacteria, where they play an important role in membrane stability and rigidity. In particular, hopanoids are thought to function as surrogates of cholesterol. Some hopanoids represent glycolipids, some examples of which are depicted in O Fig. 9. 

Examples of other antimicrobial triterpenoids from the Anthemideae tribe also included two new pentacyclic triterpenoids from Aster ageratoides Turcz. var. pilosus Willd [213] and P-sitosterol from Senecio lyratus Michaux with in vitro antifungal and antibacterial activities [214]. 

Some resonances in the ursene series have been reassigned.The labelling pattern in ursolic acid and 2a-hydroxyursolic acid isolated from tissue cultures of Isodon japonicus fed with sodium [l,2- C]acetate conforms with the original Ruzicka hypothesis for the biogenesis of pentacyclic triterpenoids. 

Oxidative rearrangement. Corey and co-workers made the suprising discovery that the 3/8,1 la-dihydroxy-A "-pentacyclic triterpenoid (1) on treatment in methylene chloride with a solution of 30% hydrogen peroxide and p-toluenesulfonic acid in t-butanol affords, after acetylation, the 1 la,12 -epoxide, with a rearranged skeletal... 

Lantana camara Linn, [bukhwebeletane, lantana] (Verbenaceae) leaf infusion is used for coughs and also against malaria, where it reduces the fever. The leaf contains anthranoids, flavonoids, polyphenols, saponins and steroids (14,15). A glycoside of pentacyclic triterpenoid oleanenoic acid isolated from the plant has molluscicidal property (56). The essential oil from its flowers and leaves contain mainly sesquiterpenes (57). 

Reviews have appeared on the occurrence of triterpenoid saponins and sapo-genins,2 the mass spectra of pentacyclic triterpenoids,8 and the possible role of triterpenoids as membrane components.4 The plenary lectures from the 12th IUPAC Symposium on the Chemistry of Natural Products have been published.5... 

The compounds (160),114 (161),115 and (162)116 have been prepared as possible intermediates for pentacyclic triterpenoid synthesis. Treatment of oleana-12,15-diene-3p,28-diol 3-acetate with toluene-p-sulphonyl chloride in pyridine affords the D(16a)-homo compound (163). The mechanisms of this and related reactions are discussed.117 2a,3[3-Diacetoxy-28-noroleana-12,17-diene has been synthesized.118... 

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