Studies On Chemical Constituents Of Acid Degradation Products Of The Total Ginsenosides From The Roots Of Panax Ginseng

Ginseng, the root of Panax ginseng C. A. Meyer, has long been prized as a panacea in Chinese medicine. Ginseng was ranked as an upper grade medicine, meaning it is nontoxic and can be used as a tonic to maintain physical vitality, in Shennong Bencao Jing, a Chinese compilation of medicinal herbs. Ginsenosides are divided into four types, oleanonic acid type, protopanaxadiol type (PPD), protopanaxatriol type (PPT), and some side-ring and skeleton changed type. PPD and PPT types are the most abundant ginsenosides, with a structure of dammarane-type tetracyclic triterpene.Numerous studies have investigated ginsenosides are the pharmacologically active constituents of Panax ginseng. Ginseng has a broad range of beneficial effects including tonic, adaptogenic, immunomodulatory, anti-inflammatory, anti-oxidant, anti-aging, anti-diabetes, anti-mutagenic, anti-cancer, cancer chemopreventive and neurovascular modulatory activities. Recent studies have demonstrated that most ginsenosides are metabolized in the gastrointestinal tract through a series of deglycosylation steps into some active partly deglycosylated saponins and aglycon derivatives. There are many studies showing that the intestinal bacterial metabolites exhibited excellent antitumor activities and were responsible for the main pharmacological activities of ginseng. It is necessary and meaningful to obtain active partly deglycosylated saponins and aglycon derivatives by acid degradation of the total ginsenosides from the roots of Panax ginseng.In the thesis, base on the summary of the chemical constituents, pharmacology, degradation methods and metabolism of ginsinosides, the acid degradation of the total ginsenosides from the roots of Panax ginseng was studied. Our investigation focused on its chemical constituents. The acid degradation products were isolated using the chromatography and recrystallizaton. The compounds were elucidated by chemical evidence and the extensive application of 1D (1H, 13C-NMR and DEPT) and 2D (COSY, HMQC, HMBC) NMR techniques. The total ginsenosides from the root of Panax ginseng were hydrolyzed for 8 h at 80°C in a solution of 50% EtOH, which contained 10% HCl. The reaction mixture was neutralized with NaOH solution and then evaporated to dryness to obtain acid hydrolysate (I). Five compounds have been isolated from the acid hydrolysate (I). The process of isolation was as follows: The acid hydrolysate (I) was subjected to silica gel chromatography and eluted with mixtures of petroleum ester and ethyl acetate (5:3) to afford four fractions (I-IV). The fraction II was further subjected to repeated silica gel column chromatography using petroleum ether and ethyl acetate (5:3) as eluent to afford crude, 20(S)-panaxadiol and 20(S)-panaxatriol were obtained by repeated recrystallization with MeOH (aqueous), dammar-(E)-20(22)-ene-3β,12β,25-triol was obtaind by further purification through octadecyl silica gel chromatography using methanol-ethyl and water (8:1) as eluent and repeated recrystallization with MeOH (aqueous). The fraction III was further subjected to repeated silica gel column chromatography using chloroform-methanol-ethyl acetate-water (8:1:8:2, lower layer) as eluents to afford crude, dammarane-3β, 12β, 20(S), 25-tetrol was obtaind by repeated recrystallization with MeOH (aqueous), dammar-24-ene- 3β, 6α, 12β, 20(R)-tetrol was by further purification through octadecyl silica gel chromatography using methanol-ethyl and water (2:1) as eluent and repeated recrystallization with MeOH (aqueous).The total ginsenosides from the root of Panax ginseng were hydrolyzed for 2 h at 80°C in a solution of 50% EtOH, which contained 2% HCl. The reaction mixture was neutralized with NaOH solution and then evaporated to dryness to obtain acid hydrolysate (II). Three compounds have been isolated from the acid hydrolysate (II). The process of isolation was as follows: The acid hydrolysate (II) was subjected to silica gel chromatography and eluted with chloroform-methanol-ethyl acetate-water (2:2:4:1, lower layer) to afford three fractions (I- III). The fraction II was further purified through octadecyl silica gel chromatography using methanol-ethyl and water (4:1) as eluent to afford crude, 25-OH-20(R)-Rg3 and 20(R)-Rh2 were obtained through repeated recrystallization with MeOH (aqueous), 20(R)-Rg3 was obtained through repeated recrystallization with ACE.