Astragalus spp

Astragalus spp. Members of this genus are included in the group of loco weeds causing disease in cattle in the United States. From A. carlei. Pease and Elderfield isolated a- and j3- earleines, which were later shown by Stempel and Elderfield to be betaine and choline respectively these are also present in A. wootoni, along with trigonelline (p. 7). ( (1) J. Org. Chem., 1940, 5, 192, see also p. 198 (2) Ibid., 1942, 7, 432 J. Amer. Chem. Soc., 1941, 63, 315. (3) Knowles and Elderfield, J. Org. Chem., 1942, 7, 389). 

Heavy metal toxicity in plants is infrequent (143). In many cases, metal concentrations in plant parts show poor correlation with soil concentrations of the element (147). Plants tend to exclude certain elements and readily accept or concentrate others. Lisk (148) reported natural plant soil concentration ratios of 0.05 or less for As, Be, Cr, Ga, Hg, Ni, and V. Cadmium appears to be actively concentrated and selenium appears to be easily exchangeable. Indicator plants are capable of markedly concentrating specific elements, e.g., Astragalus spp. for selenium (138) and Hybanthus floribundus for nickel (149). Plants growing on mine wastes have been shown to evolve populations which exhibit metal-specific tolerances (150). 

Swainsona canescens, S. luteola, S. galagfolia, Astragalus spp., Oxytropis spp. (Fabaceae)... 

The poisonous Astragalus spp. Imve been divided into groups, based upon three main types of toxicity and their effects on animals ... 

The purpose of this review is to present an overview of these secondary metabolites extracted from Astragalus spp., the newer methodology used for their isolation and structure elucidation and the biological activities of these compounds reported up to the beginning of 2000. 

Table (1) and Table (2), listed in alphabetic order, include the triterpenoid sapogenins and their glycosides (saponins), respectively, extracted fi om Astragalus spp., their structures and plant sources, covering a literature up to the beginning of2000. [146,147,219]... 

TABLE 2 List of Triterpenoid Saponins from Astragalus spp. 

The HPLC method has also been described for the determination of astragalosides in "Astragali radix" [59,92,291]. The method was sensitive, rapid and accurate and could be used for quantitative analysis of saponins. Total saponins in extract of plant of Astragalus spp. may be also determined spectrophotometrically after reaction with vanillin in acidic medium by measuring the absorbance at 560 nm (detection range is 40-200 pg) [238,321],... 

About 130 saponins have been described in Astragalus spp. untill now. Table (2). D-xylose (xyl), D-glucose (g c), L-rhamnose (rha), L-arabinose (ara) represent the carbohydrate components of these glycosides pentoses are more frequent then hexoses. Apiose (apio), in the furanosic form, occurs only in cycloaraloside C, named also astrailienin A [140,61]. Glucuronic acid has been found only in pentacyclic triterpene saponins (as in soyasaponins). Astragalus saponins of cycloartane series... 

Sesquiterpenes occur in some Astragalus spp. A. severtzovii, A sieversianus, A ugamicus, A. lasiopetalus [167], but more frequently they occur as sesquiterpene-flavonol complexes, i.e. acylated flavonol glycosides such as itom Acomplanatus [69,71,72]. From the same source, "Astragali semen", Cui et al. have also been isolated sesquiterpenoid... 

Several other activities are reported for Astragalus spp. the cycloartane saponins from A. sieversienus show an hypocholesterolemic action [219], while astramembrannin I, 87, and astrasieversianin I, 92 produce antileukocytopenic and anti-stress effects in mice [319]. Aqueous extract of A. membranaceus root causes significant stimulation of melanocyte proliferation using the sulphorhodamine B (SRB) test. This result supports the use of these extracts in traditional treatments of vitiligo [191]. 

Flavonoids isolated firom Astragalus spp. belong to the following classes of constituents flavones, flavonols, flavanones, isoflavones and isoflavans, all as aglycones than glycosides, and pterocarpans (Table 5). 

By comparison with the large variety of flavone and flavonol glycosides (these latter are the most abundant in Astragalus spp.), the number of isoflavonoid glycosides is small. Kaempferol and quercetin occur more widely among flavonols, while astragalin, 190, and rutin, 236, are the most representative glycosides. Isoflavones, isoflavans and... 

TABLE 5. Flavonoids, Aglycones and Glycosides, from Astragalus spp. 

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