Cycloartane structure

Carbonyl fimction may be also present in the cycloartane structure of genins, and the most rapresentative positions are at C-3, 6, and 16 [7,287]. In the IR spectrum of 3-oxo cycloartanes an intense band of sbc-membered cyclic ketone at 1706 cm"l is observed, and, corresponding to this, the l C NMR spectrum showed a resonance line of a ketonic carbon atom at 216.8 ppm [7]. 

More recently (2006) we performed and reported quantitative structure-activity relationship (QSAR) modeling of the same compounds based on their atomic linear indices, for finding fimctions that discriminate between the tyrosinase inhibitor compounds and inactive ones [50]. Discriminant models have been applied and globally good classifications of 93.51 and 92.46% were observed for nonstochastic and stochastic hnear indices best models, respectively, in the training set. The external prediction sets had accuracies of 91.67 and 89.44% [50]. In addition to this, these fitted models have also been employed in the screening of new cycloartane compounds isolated from herbal plants. Good behavior was observed between the theoretical and experimental results. These results provide a tool that can be used in the identification of new tyrosinase inhibitor compounds [50]. 

Astragalus genus is one of the richest source of cycloartane saponins. Oleanane type saponins are also found in Astragalus sp., but their occurrence is limited to structures common to Leguminosae. Fig (3) shows the naturally occurring cycloartanes and oleananes which have been isolated from different Astragalus species. 

Oleanane and cycloartane saponins can be isolated and structurally elucidated using similar techniques. A single chromatographic step is rarely sufficient to isolate a pure saponin from an extract. As a general rule, several preparative techniques are required to obtain the pure product. 

The natural occurrence of cycloartane triterpenoids has been reviewed.25 Acid hydrolysis of lyofolic acid, a glucoside from the leaves of Lyonia ovalifolia, afforded lyofoligenic acid (19) whose structure was established by X-ray analysis of the 3a-O-p-bromobenzoate methyl ester.26 The constitution of the genuine aglycone, protolyofoligenic acid (20), was confirmed by interrelation with cycloartenol.27... 

In a recent article by Verotta et al. [286] the structures of new cycloartane saponins from A. sieberi have been elucidated by the combination of ID- and 2D- gradient-enhanced NMR techniques H- C GHSQC, 1H-13C GHMBC, besides the DQC-COSY, E-COSY, ROESY, ID- and 2D- TOCSY experiments performed at 600 MHz. 

A similar mass spectrum, with the same base peak, is showed by cyclocephaloside I, a cycloartane-type triterpene glycoside with a 20,25-epoxy side chain (sapogenin 27), isolated from A. microcephalus, whose structure elucidation was performed by IR, and l C NMR, FABMS and chemical methods (acetylation) [42]. The H NMR spectrum of this compound shows signals from a cyclopropane methylene (H2-19) and seven tertiary methyl groups, as reported previously. 

Among cycloartane glycosides from Astragalus Turkish species, only astragaloside I (88) was able to stimulate NF-kB expression in macrophages. This implies that they are critical structural features responsible for macrophage activation by saponins [71]. 

I The saponins isolated in the plant possess aglycones of three skeletons cycloartane, ursane and oleanane, with some variation in each structure—type. It s very interesting to discover such cycloartane-type saponins, that its side-chain has been modified naturally to conjugated diene-carboxylic acid, which formed amide with 2 -amino-3, 4 -dimethyl-y-lactone moiety. 

Taxonomy Cycloartane Triterpenoids The structure was corrected (see Cycloarta-16,24-dien-3p-ol). 

Taxonomy Cycloartane Triterpenoids It is cimicifugenol whose structure was corrected. Cimicifuga simplex Wormsk. (Ranunculaceae) [1]. Mp 112-114°C (from acetone-MeOH), [a]o +20.9° (c 1. 09, CHCI3). 

Cycloartane triterpenoids are interesting not only because of the fundamental biogenesis issues. The wide variety of structures makes them attractive as subjects for chemical modification and is also responsible for the broad spectrum of biological activity. These aspects also assured the furious pace of research on this class of compounds. As a result, the number of described compounds is currently approaching 900. Their biological properties are also under active investigatiOTi. 

The chemical structure of cycloartanes is based on the 9b,19-cyclo-5a-lanostane (cycloartane) (I) skeleton. The term cycloartane evolved from the first representative of this class to be structurally characterized, cycloartenol, which was prepared from the corresponding ketone cycloartenone. Barton gave these names to the compounds because the ketone was isolated from latex of Artocarpus integrifolia L. (Moraceae) fruit [1]. Then, Spring et al. isolated cycloartenol from Strychnos nux-vomica L. (Loganiaceae) [2]. It sorni became clear that cycloartenol and its slightly polar analogs were widely distributed in the plant world. 

Actein (576) was the first cycloartane glycoside and was isolated in 1962 [3] from Actaea racemosa [Cimicifuga racemosa (L.) Nutt., Ranunculaceae]. Its structure was elucidated definitively comparatively recently [4]. 

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