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1987). In 1988 Chen et al. isolated from stems and leaves 20(R)-ginsenoside Rh2, an antitumour agent effective against the human leukaemia cell line HL-60. Zhang et al. (1989) added 20(R)-protopanaxadiol and ginsenoside Rg4 to the growing list of minor saponins and their derivatives and later additions included 20(R)-dammaran-3p,6a,12p, 20,25-pentol-6-0-a-L-rhamnopyranosyl-(1^2)-O-p-D-glucopyranoside and 20(R)-dammaran-3p,6a,12p,20,25-pentol (Zhao et al., 1990), ginsenoside F4 (Zhang et al., 1990), ginsenoside Ia (=3p,6a,12p,20(S)-tetrahydroxy-dammar-24(25)-ene-(20-0-p-D-glucopyranosyl)-3-0-p-D-glucopyranoside) (Don et al., 1996a), notoginsenoside Fe and ginsenoside Rd2 (Don et al., 1996b) and ginsenoside F5 (Don et al., 1996c).

Chang (1998) recorded the yield of crude saponins in the leaves as ca. 16.5 per cent for leaves collected in July or August and lower for later collections in September. The ginsenosides Rc, Rd and Rg1 comprised about 70 per cent of the total glycosides each month, ginsenosides Rb1, Rb2 and RC being minor components only. The ratio protopanaxadiol/protopanaxatriol was 1.13 for leaves collected in July but only 0.85 for leaves collected in September indicating that the diol yield was highest in July and the triol yield greatest in September.

Apart from saponins the leaves, which are used in ginseng leaf teas, have been shewn to yield ascorbic acid, glutamic and aspartic acids, leucine and trace elements such as calcium, sodium and potassium (Kwon et al., 1992) and neutral and acidic polysaccharides, the former comprising arabinogalactan or (1^4)-linked glucosyl residues and the latter were pectic polysaccharides with a rhamnogalacturonan spine and neutral sidechains (Gao et al., 1991). The leaves yield less polysaccharides than the roots and the roots contain mainly pectins and glucans whilst the leaves produce chiefly pectins and heteroglycans. Shin et al. (1997) isolated a complex pectic polysaccharide with a molecular mass of about 11,000 from the leaves and noted that it was a rhamnogalacturonan containing 15 different monosaccharides in its structure including the rare sugars 2-O-methyl-xylose, 2-O-methylfucose, apiose, 3-C-carboxy-5-deoxy-L-xylose (aceric acid), 3-deoxy-D-manno-2-octulosonic acid and 3-deoxy-D-lyxo-2-heptulosonic acid.

The leaves also contain fatty acids of which 80 per cent comprised linoleic, linolenic, palmitic and oleic acids (Park et al., 1986). The volatile oil, which gives the leaf its characteristic odour, is a mixture of at least 42 compounds comprising approximately 14 per cent terpenes and sesquiterpenes, 39 per cent triglycerol lipids and 22 per cent other aromatic components (Li et al., 1996a).

Saponins of Panax ginseng Flowers and Buds

The flower buds, which are normally removed before flowering in order to stimulate more active root growth, yielded the known saponins ginsenosides Rb1, Rb2, Rc, Rd, Re, Rg 1 and F3 together with a new compound ginsenoside M7cd (Yahara et al., 1979). Ginsenoside Re was the major component of the saponin fraction. Recorded yields are presented in Table 5.14.

These findings were confirmed by Shao et al. (1987) who, using column chromatography, added the known compounds ginsenosides Rf, Rg2 and Ro to

Table 5.14. Percentage saponin distribution in Panax ginseng flower buds

Table 5.14. Percentage saponin distribution in Panax ginseng flower buds

the list. Later work with cultivated Jilin (China) ginseng included the isolation of ginsenosides Ro, Rb1, Rb2, Rb3, Rc, Rd and Re, 20-gluco-ginsenoside Rf and ginsenosides Rf, Rg1 and Rg2 (Shao et al., 1989).

Jilin ginseng flower buds also yielded 0.2 per cent of volatile oil as measured by gas chromatography. The oil contained about 37 per cent sesquiterpenes together with an open chain alkane, carboxylic acids, esters and ketones (Mao et al., 1989).

Saponins of Panax ginseng Fruits

The known saponins ginsenosides Rb2, Rc, Rd, Re and Rg1 were isolated from the fruits and identified by Yahara et al. (1976). As in the leaves, ginsenoside Re was the dominant saponin. Recorded yields are summarised in Table 5.15.

Additional minor compounds found subsequently included ginsenoside Rb1 (Bai et al., 1988) and 20(R)-ginsenoside Rh2 and 20(R)-ginsenoside Rg3 together with 20(R)-protopanaxatriol (Zhao et al., 1993).

Non-saponin compounds found in the fruits included ^-sitosterol and daucosterol (Zhao et al., 1993). Although the total content of free and bound lipids in various parts of the plant varied from 0.91 to 3.48 per cent, the yield from seeds was about 15.08 per cent. The seed fatty acid composition was different, oleic and linoleic acids forming approximately 51.21 and 37.46 per cent respectively (Choi et al., (1983). The oil from the seeds of P. ginseng also yielded lipids. Squalene, a biosynthetic precursor of sterols, formed 54 per cent

Table 5.15. Percentage saponin distribution in Panax ginseng fruits

Designation

Prosapogenin

Recorded yield per cent

Ginsenoside Rb2

Protopanaxadiol

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