Nadia A. El-Sebakhy

Cycloartane triterpene glycosides from Astragalus trigonus

Three new cycloartane glycosides, trigonoside I, II and III, and the known astragalosides I and II were isolated from the roots of Astragalus trigonus. The structures of the new glycosides were totally elucidated by high field (600 MHz) NMR analyses as cycloastragenol-6-O-beta-xylopyranoside, cycloastragenol-3-O-[alpha-L-arabinopyranosyl(1-->2)-beta-D- xylopyranosyl]- 6-O-beta-D-xylopyranoside and cycloastragenol-3-O-[alpha-L-arabinopyranosyl (1-->2)-beta-D-(3-O-acetyl)-xylopyranosyl]-6-O-beta-D-xylopyranoside.

Sesquiterpene xylosides from Iphiona scabra

Abstract The aerial parts of Iphiona scabra afforded a complex mixture of sesquiterpene xylopyranosides. Separation of the peracetylated derivatives gave 10 compounds, seven eudesmane derivatives, a secoeudesmane and two sesquiterpene glycosides with new skeletons, named iphionane and isoiphionane. The biogenesis of these compounds is discussed.

Cycloartane triterpene glycosides from Astragalus alexandrinus

Abstract Alexandroside I, a new cycloartane triterpene glycoside was isolated from Astragalus alexandrinus. Its structure was established as 3-O-β- d -glucopyranosyl-9β,19-cyclolanost-3β,6α,16β,24(R),25 pentaol on the basis of spectroscopic and chemical methods. Four known glycosides, astraversianins VI, X, XIV and XV, were also isolated.

Cycloartane triterpene glycosides from Egyptian Astragalus species.

Abstract Tomentoside I, a new tetranor-cycloartane triterpene glycoside was isolated fromAstragalus tomentosus. Its structure was established as 6α-acetoxy-23-ethoxy-16β,23(R)-epoxy-24,25,26,27-tetranor-9,19-cyclolanosta-3β-O-xyloside, on the basis of spectral evidence. 3-O-Methyl-chiro-inositol ether was also isolated and identified. The known compound, astragaloside II, previously isolated fromA. spinosus, was also identified.

Cycloartane and oleanane saponins from Astragalus sp.

Abstract Astragalus spp. (Leguminosae) represent a valid rural crop of ecological importance in many countries, and some species serve as foodstuffs and pharmaceutical emulsifiers. Astragalus species are used in Chinese traditional medicine as antiperspirant, antihypertensive, antidiabetic, diuretic and tonic. The pharmacologically active constituents of these Astragalus are of two different types, polysaccharides and saponins, and the most interesting pharmacological properties are hepatoprotective, immunostimulant and antiviral. Astragalus species are a source of cycloartane type saponins, derived from cycloartenol by oxidation at C-6, C-16, C-20, C-23, C-24, followed by possible ring closures with the formation of a 20,24-epoxide (cycloastragenol or cyclogalegenin) or a 20,25-epoxide, or a 16,24-20,24- diepoxide (cycloalpigenin), or a 16,23-16,24-diepoxide (cycloorbigenin B). Approximatively 100 saponins mainly derivatives of the 20( R ),24( S ) form of cycloastragenol [3β,6α,25-tetrahydroxy-20( R ),24( S )-epoxy-9,19-cyclolanostane], (astragalosides or astraversianins), and more rarely of the 20( S ), 24( R ) form (cyclogalegenin), have been isolated. Some species also contain trihydroxyolean-12-ene saponins. Details on the isolation, purification and structural elucidation, along with recent results on the pharmacological properties of Astragalus cycloartane and oleanane saponins, will be discussed.

Cycloartane triterpene glycosides from Astragalus sieberi

Abstract Two new cycloartane saponins were isolated from the aerial parts of Astragalus sieberi. The structures were elucidated by 1D- and 2D- gradient-enhanced NMR analyses and enzymatic hydrolysis as 20(S),24(R)- epoxy -9β,19- cyclolanostan -3β,6α,16β,25- tetrol -3-O-β- d -glucopyranoside and 20(S),24(R)- epoxy -9β,19- cyclolanostan -3β,6α,16β,25- tetrol -3-O-β- d -glucopyranosyl -(1 → 2)-β- d - glucopyranoside .

A cycloartane triterpene 3β, 16β diglucoside from Astragalus trigonus and its non natural 6-hydroxy epimer

Abstract The detailed investigation of Astralagus trigonus DC roots, led to the isolation of a new cycloartan-3β, 16β diglucoside, whose structure was elucidated by extensive use of 1D- and 2D- high field (600 MHz) NMR techniques. The NaBH 4 reduction of the natural 6-oxo 3β, 16β diglucoside, previously isolated from the same plant, afforded the 6-epi-derivative of the new compound. The conformational preference of both these compounds has been investigated by high field 1 H NMR spectroscopy and molecular modeling techniques.

Chemical constituents from Astragalus annularis Forssk. and A. trimestris L., Fabaceae

The phytochemical investigation of the aerial parts of Astragalus annularis Forssk. and A. trimestris L., Fabaceae, growing in Egypt, resulted in the isolation of eight compounds, for the first time from these two species. These compounds were identified by chemical methods, NMR spectroscopy, UV spectroscopy as well as MS analysis. The antimicrobial activity of the isolated compounds were tested against Staphylococcus aureus, Esherichia coli and Candida albicans.

(−)-(R,R)-7′-O-methylcuspidaline from the leaves of Aristolochia elegans

Abstract The chloroform extract of the defatted leaves of Aristolochia elegans has yielded a bis-1-benzyltetrahydroisoquinoline alkaloid with one diphenyl ether link between rings C and C′. On the basis of spectroscopic analysis this has been identified as the previously unreported (−)-( R,R )-7′- O -methylcuspidaline.

Hepatoprotective effects of Astragalus kahiricus root extract against ethanol-induced liver apoptosis in rats

The hepatoprotective activity of the ethanol extract of Astragalus kahiricus (Fabaceae) roots against ethanol-induced liver apoptosis was evaluated and it showed very promising hepatoprotective actions through different mechanisms. The extract counteracted the ethanol-induced liver enzymes leakage and glutathione depletion. In addition, it demonstrated anti-apoptotic effects against caspase-3 activation and DNA fragmentation that were confirmed by liver histopathological examination. Moreover, the phytochemical study of this extract led to the isolation of four cycloartane-type triterpenes identified as astrasieversianin II (1), astramembrannin II (2), astrasieversianin XIV (3), and cycloastragenol (4). The structures of these isolates were established by HRESI-MS and 1D and 2D NMR experiments. The antimicrobial, antimalarial, and cytotoxic activities of the isolates were further evaluated, but none of them showed any activity.