Abe and Saito in 1922 and Yonekawa in 1926 obtained a relatively pure glycoside, ginsenin, from Korean ginseng root and Kotake in 1930 isolated a glycoside called panaxin, which did not demonstrate typical haemolytic characteristics, but hydrolysis with methanolic 50 per cent sulphuric acid produced a prosapogenin, a-panaxin, C38H66O12, which could be further hydrolysed with fuming hydrochloric acid to yield glucose and a chlorinated aglucone, C30H53O3Cl (Hou, 1978). Many years later it was confirmed that Garriques' panaquilon (1854), Yonekawa's ginsenin (1926) and Kotake's panacin (1930) were indeed identical and that panacon (Garriques, 1854), the noncrystalline compound with a melting point exceeding 270° C reported by Asahina and Taguchi in 1906 and a-panaxin (Kotake, 1930) were identical with the prosapogenin actually melting at 330° C (Fujita, Itokawa and Shibata, 1962).
Nevertheless further progress on the isolation and characterisation of ginseng glycosides was very slow. Unlike the alkaloids which could be readily isolated as salts and had been discovered in quick succession after the first such compound, morphine in opium, had been isolated by the German apothecary Wilhelm Sertürner in 1817, glycosides presented much greater difficulties being usually high molecular weight, sugar-linked compounds that would readily hydrolyse and so lose part or the whole of the solubilising side-chains which were often composed of mixed sugars. Therefore progress in the isolation and characterisation of the complex glycosides in the pharmaceutically important species of the genera Digitalis, the fox-gloves yielding cardenolide glycosides, Drimia, the squills producing bufodienolide cardiac glycosides and Panax, the ginsengs containing triterpenoid saponin glycosides, was restricted until the development of efficient new separation techniques including, in particular, chromatographic methods, and sophisticated, diagnostic, instrumental techniques such as spectrometry from 1960 onwards.
In the period up to the 1960's other workers had discovered in various Panax species sugars such as glucose, arabinose, sucrose and rhamnose, sterols such as ^-sitosterol and stigmasterol, high molecular weight fatty acids (panax acids), fatty acid esters and the triterpenoid genin oleanolic acid (Lin, 1961). However it was not only the development of new analytical techniques that stimulated research into the phytochemistry of ginseng. In Russia (1957) Professor Israel Brekhman and in Bulgaria (1959) Professor Wesselin Petkov had independently studied the pharmacological features of ginseng and, although their ideas were not universally accepted by pharmacologists, they did prompt chemists in Russia and Japan to research the chemistry of the controversial Panax species.
It is generally considered that the most important compounds occurring in ginseng roots form a complex series of closely related triterpenoid saponin glycosides, sugar-linked chemicals possessing the property of lowering the surface tension of water with consequent soap-like frothing or lather formation on shaking; hence the name "saponin". In addition typical saponins possess a bittersweet taste and are sternutatory as such compounds irritate nasal mucous membranes with consequent sneezing. Saponins are toxic to cold-blooded animals including insects and molluscs although not normally affecting warmblooded animals. However, saponins do form colloidal aqueous solutions that can cause haemolysis of red blood cells and are therefore dangerous if injected into the human blood stream (Trease and Evans, 1993; Harborne and Baxter, 1993). The saponin glycosides were thought at first to be responsible for most of the recorded biological effects of ginseng and its preparations.
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