Isolation And Chemical Characterization Of Bioactive Principles From Swertia Franchetiana

'Zang-Yin-Chen' ( ZYC) is a traditional Tibetan medicine for the treatment of hepatitis and cholecystitis. The plant Swertia franchetiana Smith (family Gentianaceae) is distributed in Qinghai-Tibet Plateau and used as plant materials of ZYC. In order to clarify the chemical foundation of this herb, the dissertation describes the preparation, isolation and characterization of bioactive principles from S. franchetiana. The main research results are as follows:The methanol crude extract of ZYC was screened by means of combined HPLC-UV-MS technique. The structural information was obtained from on-line UV and MS spectra at the early stage of preparative isolation. Phytochemical investigation of liposoluble fractions of the methanol extracts led to the isolation of fourteen pure compounds including eleven xanthone aglycones, of which seven compounds were isolated from this plant for the first time. Additional twenty-four compounds were isolated and characterized from n-BuOH fractions of methanol extracts from ZYC. Among them, two new iridoid glycosides and two new xanthone glycosides were obtained by means of preparative HPLC. The other 4 iridoid glycosides and 7 xanthone glycosides, together with isovitexin and erythrocentaurin, were all firstly found from this plant. Besides, two minor compounds from an aqueous fraction were tentatively identified as two new iridoid glycosides by means of HPLC-UV-MS analysis.Five xanthones from this plant were tested for the properties of radical scavenging by means of oscillopolarography and fluorescent spectrophotometry, and showedcapacity to scavenge both superoxide anion radical and hydroxyl radical. Bellidifolin was further tested for the protective activity on cerebral-ischemia animals in vivo. The results revealed that Bellidifolin possessed potent brain-protective activity and showed prospects of pharmaceutical application.The 1H and 13C NMR data of natural xanthones from ZYC and literatures were analyzed and summarized. Some rules of 1H and 13C chemical shifts were deduced in order to supply a theoretic reference for the NMR characterization of natural xanthone compounds.