Lupanes

The plant is used to treat leprosy the roots are used to heal ulcers and to cure ringworm infection. A decoction of the leaves is drunk to treat tuberculosis and to improve general weakness. In Cambodia, Laos, and Vietnam, an infusion of the bark is used to correct nervous affections. The plant is known to elaborate lupane triter-pene saponins and kaurane diterpenes including 16-aH, 17-isovalerate-ent-kauran-19-oic acid, which strongly inhibited the enzymatic activity of cyclooxygenase in vitro (76,77). 

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]. 

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]. 

G. Culioli, C. Mathe, P. Archier, C. Vieillescazes, A lupane triterpene from frankincense (Boswellia sp., Burseraceae), Phytochemistry, 62, 537 541 (2003). 

Figure 3.7 Scheme of fragmentation for lupane type molecules that leads to the formation of the characteristic ion fragment at m/z 189... 

Regert et al. studied [9] a series of 30 Neolithic hafting adhesives from lake dwellings at Chalain (France) using an analytical procedure based on GC/MS analysis involving solvent extraction (dichloromethane) and trimethylsilylation. In the majority of the samples a series of triterpenoid compounds with a lupane structure was clearly identified on the basis of their TMS mass spectra. In particular, the presence of betulin, betulone, lupenone, lupeol and lupa-2,20(29)-dien-28-ol allowed birch bark tar to be identified. In other samples the co-occurrence of other plant biomarkers such as a-amyrin,(3-amyrin... 

Triterpenoid saponins are synthesized via the isoprenoid pathway.4 The first committed step in triterpenoid saponin biosynthesis involves the cyclization of 2,3-oxidosqualene to one of a number of different potential products (Fig. 5.1).4,8 Most plant triterpenoid saponins are derived from oleanane or dammarane skeletons although lupanes are also common 4 This cyclization event forms a branchpoint with the sterol biosynthetic pathway in which 2,3-oxidosqualene is cyclized to cycloartenol in plants, or to lanosterol in animals and fungi. 

Scheme 39 Bi(0Tf)3 xH20-catalyzed Wagner-Meerwein rearrangement of lupanes...

King RB, Silaghi-Dumitrescu I, Lupan A (2005) Dalton Trans 1858... 

The structure of benulin (134), a lupene hemiacetal from Bursera arida, has been confirmed by X-ray analysis. An investigation of several Senecio species has resulted in the isolation of a series of lupane derivatives which include the acids (135), (137), and (139), the corresponding aldehydes (136), (138), and (140), the ketone (141), and betulonic acid. Three more triterpenoids (142)—(144) have... 

Acid-catalysed isomerization of the olefins (153)—(155), obtained on decarboxylation of lupan-28-oic acid, resulted in the formation of the lup-17-ene derivative (156) with inversion at C-19 and not 28-norlup-13(18)-ene (157) as previously suggested.Further studies have been reported on a series of lupan-12-one" " and 29-hydroxy-30-norIupan-20-one (158) derivatives. The nitrone (159) and the N-hydroxy-Iactam (160) were produced on irradiation of 3 -acetoxy-28-nitrosyloxylupane (161). ... 

These processes are normally enzyme-catalyzed. Purefy ctemical processes are seldom encountered with carbon conq)ounds in nature. The few exceptions include the very act of phenol coupling (by which racemic compounds are obtained), cyclization reactions ofpolyprenyl compoimds (which benefit from the preferred conformation of the reaction partners, suitable for the cyclization, Wendt 2000), and Diels-Alder cycloadditions. The latter have been advocated for the biosynthesis of celastroidine A (= volubilide) from a lupane triterpene and an abietane diterpene in two different plants, Hippocratea celastroides Kunth from Mexico (Jimenez-Estrada 2000) and Hippocratea volubilis Linnaeus (Alvarenga 2000). 

Phytochemical studies of these species led to the isolation and structural characterization, by NMR and MS analysis, of many secondary metabolites, mainly flavonoids, and expecially flavonol glycosides, clerodane diterpenes, and triterpenes having the lupane, ursane, and oleanane skeletons. Particularly flavonoids and their glycosides have a chemotaxonomic interest in the genus and in general in the Chrysobalanaceae family. 

In the course of our phytochemical work we studied seven Licania species all belonging to Venezuelan flora, collected in Puerto Ayacucho, Estado Amazonas and in the Parque Nacional Henry Pittieri, Maracay, Estado Aragua. A number of new and known secondary metabolites, mainly flavonoids, especially flavonol glycosides, sterols, and triterpenes having the lupane, ursane, and oleanane skeleton were isolated and characterized. The last part of this chapter deals also with the isolation of clerodane diterpenes from the methanol extract of L. intrapetiolaris by Oberlies et al., 2001 [4]. All the Licania species investigated up to now are reported in Table 1. 

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