Studying extraction techniques for polyacetylene compounds in white ginseng root and using various solvents, Nho and his colleagues (1990) concluded that refluxing with methanol was the most efficient of the seven solvent systems investigated although Soxhlet extraction was almost equally effective. The solvents in order of decreasing efficiency were methanol, methylene dichloride, acetone, diethyl ether, ethyl acetate, methyl cyanide and petroleum ether. Panaxynol and panaxydol were the principal polyacetylenes present, the yield being 4.2 mg/g and 6.4 mg/g respectively. Continued interest in these compounds led to the isolation from the hexane extract of P. ginseng roots of a series of new polyacetylenes which were designated ginsenoynes A-E and acetylated ginsenoynes F-K (Hirakura et al., 1991, 1992)(see Appendix to Chapter 5). Later Hirakura et al. (1994) described the isolation and characterisation of the linoleoylated polyacetylenes panaxynol linoleate, panaxydol linoleate and ginsenoyne A linoleate from the root of P. ginseng.
Not surprisingly ginseng roots yield about 5 per cent by weight of sugars which include the monosaccharides D-glucose, D-fructose and D-rhamnose, the disaccharides sucrose and maltose, and trisaccharides such as a-maltosyl-jS-D-fructofuranoside, O-a-D-glucopyranosyl-(1^2)-O-^-D-fructofuranosyl (1^2)-^-D-fructofuranoside and O-a-D-glucopyranosyl-(1^6)-O-a-D-glucopyranosyl-(1^4)-O-a-D-glucopyranose. The principal sugar in fresh white ginseng root is sucrose, forming 92-94 per cent in 2 year old roots but decreasing in older roots (Sohn et al., 1988). In red ginseng root the main sugars are sucrose and rhamnose.
Polysaccharides or glycans are usually defined as polymers of monosaccharides and their derivatives comprising ten or more units, the upper limit exceeding 1000 units. Polysaccharides are present in all parts of the ginseng plants although the roots contain greater amounts than in the rhizomes, stems and leaves in decreasing order and the main roots yield more than the lateral roots. The crude polysaccharide fraction can be obtained by extraction with boiling water with a yield of about 8-10 per cent. The roots produce mainly pectins and glucans and the leaves pectins and heteroglycans (Gao et al., 1989). Pectin (some 20 per cent of the polysaccharide fraction) and the ubiquitous starch (some 80 per cent) are the major polysaccharide components found in ginseng roots. Pectic substances occur in primary cell walls and intercellular cement and are mixtures and/or chemical combinations of ara bans, galactans and methyl esters of galacturonans. Arabans possess a low molecular weight branched chain structure comprising a(1^5)- and a(1^3)-L-arabinofuranose units. Galactans form straight chains of up to 120 units comprising ^-(1^4)-D-galactopyranose units. Pectins may contain 200 or more units of a-(1^4)-D-galactopyranosyluronic acid. Ginseng pectin, which was estimated as 7.5711.09 per cent of dried ginseng samples, comprises galactose, galacturonic acid, arabinose and rhamnose residues in the molar ratio 3.7:1.7:1.8:1 in a highly branched molecule with ^-(1^3)-D-galactan as its backbone and (1^4)-galacturonic acid, (1^3)- or (1^2,4)-rhamnose and (1^5)- or (1^3,5)-arabinose residues in the side chains together with some (1^6)-linked galactose residues. The crude polysaccharides were shewn to contain ~5 per cent of proteins including aspartic acid, threonine, serine, glutamic acid, glycine, alanine, valine, methionine, isoleucine, leucine, tyrosine, phenylalanine, lysine, histidine and arginine (Li et al., 1986, 1987).
Several acidic branched chain heteroglycans with molecular weights varying from 20,000 to ca. 1,900,000 have been reported in roots, stems, leaves and tissue cultures of various Panax species. Sanchinan A, molecular weight 1,500,000, is an arabinogalactan containing about 3.27 per cent protein, from Sanchi ginseng P. notoginseng (Ohtani et al., 1987); hetero-polysaccharide PN from P. ginseng leaves, molecular weight about 1,900,000, is comprised of arabinose, galactose, glucose, rhamnose, xylose and galactosamine in the ratio 8.1:12.5:4.1:0.8:1.0:1.6 (Liu et al, 1988) and the ginsenans PA and PB (Takeda et al., 1993) from P. ginseng roots have molecular masses of 160,000 and 55,000 respectively, ginsenan PA being composed of units of L-arabinose, D-galactose, L-rhamnose, D-galacturonic acid and D-glucuronic acid in molar ratios of 11:22:1:6:1 and ginsenan PB possesses hexuronic residues as methyl esters. Further analysis revealed principally a-arabino-^-3,6-galactan and rhamnogalacturonan type units. The acidic arabinogalactans ginsenans S-IA and S-IIA also from P. ginseng roots comprised L-arabinose, D-galactose and D-galacturonic acid in the molar ratio 8:8:1 and L-arabinose, D-galactose, D-glucose and D-galacturonic acid in the molar ratio 15:10:2:5 respectively. In these compounds the hexuronic acid residues are also methyl esters and the main spine is a-1,5-linked-L-arabino- (i-3,6 branched-D-galactan (Tomoda et al., 1993). The compounds are important as immunostimulatory, antitumour and anticomplementary properties have been claimed.
An interesting series of high polymer peptidoglycans, the panaxans designated A to U, were isolated and characterised by Hikino and his co-workers (19841986) using diluted methanol extraction followed by fractionation on a series of columns of cellulose, DEAE-cellulose, Sepharose 6B, Sephacryl-S-500 and Sephacryl-S-200. Panaxan A had a molecular weight of ca. 14,000 and panaxan B was estimated at ca. 1,800,000; these compounds comprised recurring a-(1^6)-linked D-glucopyranose units with branching at one a(1^3) position in each unit and non-reductive terminals at fixed intervals (Tomoda et al., 1985). The marked hypoglycaemic activity of these compounds in normal and alloxan-induced hyperglycaemic mice suggested potential therapeutic value.
Peptides have also been reported. Using a methanol/water (1:1) extract of white ginseng and paper electrophoresis (30V/cm, AcOH/AcONa buffer, pH 5.0), Gstirner and Vogt (1966) isolated some low molecular weight peptides of uncertain pharmacological activity. The peptides were concentrated by 2-dimensional high voltage electrophoresis on Sephadex G-50 (1000V, 8 hr) to yield four low molecular weight compounds. Subsequent hydrolysis of these isolated peptides (concentrated HCl/90(%) HCOOH (1:1), 120° C, 36 hr) and analysis by the Stein-Moore method on Amberlite IR-120 yielded the neutral amino acids alanine, glycine and serine, the acidic amino acids aspartic acid and glutamic acid and the basic amino acid arginine as common components. In addition fraction 1 contained threonine, proline (major component), leucine, isoleucine, lysine and histidine, fraction 2 threonine, valine, ^-aminobutyric acid, ^-aminoisobutyric acid, lysine, histidine, hydroxyproline and two unidentified compounds, fraction 3 threonine, proline (major component), methionine, leucine, alloisoleucine, isoleucine, phenylalanine, ^-aminobutyric acid, tyrosine, lysine and histidine and fraction 4 an unidentified component. Tryptophan was not found in any fraction. Examining red ginseng and Korean, Canadian and American white ginsengs, Lee et al. (1982) noted that 15 common free amino acids occurred, the yield being lower in red ginseng than in dried white ginseng. The basic amino acid arginine comprised 68-72 per cent of the total amino acids and methionine and phenylalanine were not detected in extracts of red ginseng. Liu et al. (1990) examined the distribution of amino acids in P. ginseng roots and recorded a highest yield in the budding period (April), less in the dying-down phase in September and much less during the flowering-fruiting period in June. They also noted that the main root yielded higher levels of amino acids than the lateral roots.
Recently (1998) Chen et al. reported the discovery of a series of six oligopeptides related to oxidised glutathione in aqueous-methanol extracts of P. ginseng roots. The compounds were:—P-I=N-y-glutamylcystinyl-bis-glycine, P-II=y-glutamylcysteinglycine disulphide, oxidised glutathione, P-III=N,N'-bis-y-glutamyl-cystylglycine, P-IV=y-glutamylcysteinylglycinamide disulphide, P-V=N-y-glutamyl-glycylcysteine disulphide and P-VI=y-glutamylarginine. Compound P-V, a novel compound, has somnogenic properties.
Hiyama et al. (1978), employing HPLC analysis with a TSK gel LS160 column and water and G-3000W and G-2000W columns and H2O/AcOH/Et3N (100:0.3:0.3) solvent, demonstrated the presence of uridine, guanidine and adenine in white ginseng root and uracil, uridine and adenosine in lateral roots. Okuda's group found a peptide of molecular weight 1000 as well as the purine nucleoside adenosine which has hypoglycaemic activity (Hou, 1978).
Polyamines also have been reported. Putrescine was shewn to be the major polyamine in ginseng seedlings although spermidine was dominant in 2-year old plants and spermine was also present (Cho et al., 1989).
Alkaloidal components were isolated in small amounts only from powdered roots. N9-formylharman, ethyl-^-carboline-1-carboxylate and perlolyrine (Han et al., 1986), the water-soluble alkaloid spinacine (4,5,6,7-tetrahydroimidazo (4,5-c)pyridine-6-carboxylic acid (Han et al., 1987) and, from the ether-soluble fraction, 4-methyl-5-thiazoleethanol, norharman and harman (Park et al., 1988) were recovered.
The presence of phenolic substances such as salicylic and vanillic acids was indicated earlier and recent work involving gas-liquid chromatography (Park et al., 1994) confirmed the presence of eight such aromatic acids (caffeic, cinnamic, ferulic, gentisic, p-coumaric, salicylic, syringic and vanillic acids) in white ginseng roots. Other organic acids reported included fumaric, succinic, maleic, malic, citric and tartaric and the unsaturated fatty acids oleic, linoleic and linolenic (Lee and Lee, 1961).
Trace mineral and rare elements occur in all species of ginseng. An aqueous extract contains elements such as aluminium, arsenic, boron, calcium, cobalt, copper, iron, magnesium, manganese, molybdenum, potassium, phosphorus, sodium, sulphur, vanadium and zinc as well as silicate ions (Hou, 1978). Greater amounts of trace elements were detected in leaves and stems than in roots and cultivated roots contained less trace elements than wild ginseng roots. Iron, manganese and zinc were the most important, being in highest yield in roots in about September (Zhao et al., 1993), but more recent work has concentrated on the analysis for germanium and selenium in ginseng. Traces of rubidinium and strontium were also reported and cadmium and lead levels were found to be far below the toxic doses (Cai and Guo, 1992; Jiasheng et al., 1994). Although trace elements are detected only in parts per million or parts per billion, they are regarded as essential for the maintenance of good health and there is much debate about their precise functions, deficiencies being related to the onset of carcinomas and endemic diseases and the breakdown of immunological defences (Lovkova et al., 1996).
Other common plant constituents such as nucleosides, sterols, lipids and inorganic ions have also been recorded.
Commercially ginseng (Panax ginseng) is available in white and red forms. Careful chemical analysis has revealed marked differences between the two types. The airdried white ginseng as described above yielded the range of ginsenosides discussed but the heat treated red ginseng revealed some changes. Common to both varieties were the ginsenosides Rb1, Rb2, Rc, Rd, Re, Rf, Rg1, Rg2, Rg3, Rh1 and Ro but red ginseng was found to yield greater amounts of the ginsenosides Rg2, Rg3 and Rh1 Compounds apparently specific to red ginseng included 20(R)-ginsenoside Rg2, 20(S)-ginsenoside Rg3, 20(R)-ginsenoside Rh1 and ginsenoside Rh2 (Kitigawa et al., 1983b). Subsequent work by Kasai, Matsuura and colleagues (1983, 1984) revealed the presence of additional saponins in extracts of red ginseng, including ginsenosides Ra1, Ra2, Ra3, Rs1, Rs2, notoginsenosides R1 and R4 and quinquenoside R1 (see Appendix to Chapter 5 for chemical structures). Kitigawa and his team (1987) further investigated the total saponins of white and red ginseng, employing drugs prepared from the same sample of Panax ginseng and a thin layer chromatography technique involving a chromatoscanner. It was concluded that the variation between the two drugs was due to heat processing changes causing a) demalonylation of the malonyl-ginsenosides occurring in the fresh root, b) elimination of the glycosyl residue at C-20 of the aglycone units in the ginsenosides, and/or c) isomerisation of the hydroxyl configuration at C-20 of the aglycones. Therefore heat processing changes must also occur during the preparation of commercial aqueous extracts and decoctions of ginseng and, as such preparations tend to be acid in the pH range 4.8-5.3, hydrolysis of the C-20 linkage with accompanying epimerisation at the C-20 carbon atom will take place. Resultant compounds may affect the pharmacological characteristics of the final product.
Further dammarane ginsenosides have been reported as isolated after processing from Korean red ginseng root viz. ginsenosides Rg4 and Rg5 (Kim et al., 1996), ginsenoside Rh4 (Baek et al., 1996a), 20(E)-ginsenoside F4 (Ryu et al., 1996) and ginsenoside Rg6 (Ryu et al., 1997).
Employing alcian blue dye complex formation and spectrophotometry Han et al. (1992) confirmed that the polysaccharide yield from red ginseng after aqueous extraction was three times greater than from fresh root. The main roots yielded more polysaccharide than fine roots and the polysaccharides were located mainly in the cortex and cambium. Do et al. (1993) used a colorimetric method employing carbazole-sulphuric acid to measure the quantities of acidic polysaccharides in various ginsengs. They also concluded that the yield of polysaccharides from red ginseng root (P. ginseng) was higher than from white ginseng root, wild and cultivated American ginseng (P. quinquefolium) root, Sanchi ginseng (P. notoginseng) root and ginseng leaves.
Red ginseng was shewn to yield 724, 721 and 71 ¡g/g respectively of the polyacetylenes panaxynol, panaxydol and panaxytriol, estimation being performed using a capillary gas chromatographic method and a flame ionisation detector (Nho and Sohn, 1989). Another report recorded 250, 297 and 320 ¡igj g respectively of the same polyacetylene compounds (Matsunaga et al., 1990). Using repeated column chromatography Baek et al. (1996b) discovered panaxynol, panaxydol, ginsenoyne A and panaxydiol chlorhydrin in red ginseng rhizomes.
Among the nonsaponin constituents of red ginseng was the food flavouring agent 3-hydroxy-2-methyl-pyran-4-one and its glucoside, which were recovered from an ethanol extract of red ginseng by ether extraction and silica gel chromatography (Wei, 1982). Such compounds may be artifacts generated during preparation of the red ginseng.
(5-14) 3-hydroxy-2-methyI-pyran-4-one 3-0-(3-D-glucopyranoside
New amino acid derivatives maltulosyl-arginine and arginylfructose were isolated from Korean red ginseng and it was noted that red ginseng contained much more of the first-named compound than white ginseng, suggesting that it could be derived by the Maillard reaction of maltose with arginine under acid o
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