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to qualitative analysis and accurate quantitative estimation and therefore to quality control of the ginsenosides in mixtures. Nevertheless the newer planar methods such as Overpressure Layer Chromatography (OPLC), Centrifugal Layer Chromatography (CLC) and Sequential Centrifugal Layer Chromatography (SCLC) have also been used for the separation of the major ginsenosides on the laboratory scale. Multi-step procedures involving column chromatography on silica gel, the slower process of Drop Counter Current Chromatography (DCCC) and the techniques of preparative HPLC (Paik et al., 1982) have been used for larger scale isolations.

Sanada et al. (1974, 1978) demonstrated the simplicity and effectiveness of the separation of the 11 common ginsenosides on silica gel H thin-layer plates using the upper phase of n-butanol: ethyl acetate: water (4:1:5) or the lower phase of chloroform: methanol: water (65:35:10) mixtures. Their fractionation methods, involving methanol, water, ether and n-butanol extractions followed by silicic acid and silica gel chromatography, were summarised by Shibata et al. (1985).

Further glycosides were isolated from the roots and characterised including ginsenosides Ra! and Ra2 (Besso et al., 1982a), ginsenoside Ra3 from both white and red ginseng (Matsuura et al., 1984), the malonyl ginsenosides Rb^ Rb2 and Rd (Kitagawa et al., 1983a, 1989; Wang et al., 1993) and the minor dammarane saponins koryoginsenosides R! and R2 (Kim et al., 1995) (see Appendix to Chapter 5).

The ginsenosides of P. ginseng roots fall into at least 4 groups, protopanaxadiol type (Table 5.3), protopanaxatriol type (Table 5.4), oleanane type (Table 5.5) and miscellaneous types (Table 5.6).

Commercial ginseng roots yield about 0.05 per cent of volatile oil although fresh roots may yield up to 0.9 per cent volatile oil. The oil is responsible for the aroma of fresh ginseng but the smell is not easily detected in the powdered or dried drug after storage. The reported composition of the oil depends on the method of extraction e.g. steam distillation, ether extraction, freeze-drying and vacuum distillation, etc. Using combined gas/liquid chromatography and mass

THE PRINCIPAL ACTIVE CHEMICALS IN PANAX SPECIES Table 5.3. Structure of protopanaxadiol type ginsenosides

THE PRINCIPAL ACTIVE CHEMICALS IN PANAX SPECIES Table 5.3. Structure of protopanaxadiol type ginsenosides

Designation R, R

Ginsenoside

Ra,

-Glc2-Glc

-GIc(,-Ara(p)4-XyI

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