|其他摘要||In China the modernization of Traditional Chinese Medicine is based on the research of the sustainable development of medical plants resources. The phytochemical investigation on medicinal plants will provide strong support for promotion of the sustainable development by means of modern scientific technology.
This thesis focuses on not only the discovery of new natural compounds from six medicinal plants in west China (Gentiana rigescens Franch ex. Hemsl., G. rhodantha Franch ex. Hemsl., G. straminea Maxim, Phyllanthus urinaria, Dracaena argustifolia and D. cambodiana), but also the resources investigation of these plants. 146 compounds, including iridoidal glycosides, xanthones, flavonoids and phenolic glycosides, as well as triterpenoid and steroidal saponins, have been purified and identified. Among of them, there are 48 new compounds. Bioactive assay showed that some triterpenoids and steroids have antifungal activity, while phenolic glycosides displayed inhibitory activity on tyrosinase and acetylcholinesterase. Moreover, the thesis established HPLC analytical methods for quality control of two medicinal plants, Gentiana rigescens and Phyllanthus urinaria. The methods for large scale isolation and purification of gentiopicroside and corilagin from plants were also invented.
The thesis consists of the following four chapters.
Chapter 1. As a part of our research on Gentianaceous medicinal plant, three species from genus Gentiana, G. rigescens, G. rhodantha, and G. straminea, were systematically studied, which led to the isolation of 100 compounds. Among of them, there are 32 new compounds, including six new 20S,25-epoxy dammarane triterpenoids. A possible biogenetic pathway of the isolated iridoidal compounds, the major components in G. rigenses was proposed.
In addition, a rapid, sensitive and selective quantitative analytical method was established by HPLC, for the analysis of loganic acid, swertiamarin, gentiopicroside, sweroside and 2'-(o,m-dihydroxybenzoyl)-sweroside, the five major bioactive compounds in roots of G. rigescens. It can be readily utilized as a suitable method for the quality control of G. rigescens.
Moreover, a method for large scale isolation and purification of gentiopicroside from Gentiana spp. was invented, which is low-cost and suitable for industrial use.
The above research results showed the significance of molecular diversity in genus Gentiana for not only the discovery of new bioactive natural products, but also the sustainable ultilization of its plant resources. The phylogeny of genus Gentiana was discussed on the basis of the biosynthetic pathway of iridoid glucosides, the major components in this genus. And, the rules of accumulation and distribution of the secondary metabolites in the plants and its significance for chemotaxonomy is discussed.
Chapter 2. Liliales that contains steroidal glycosides as main constituents is an important group in Monocotyledons. Many of them are important medicinal plants. In order to further investigate the molecular diversity of natural steroids and to discover bioactive products, 2 species (Dacaena angustifolia and D. cambodiana) were studied. 31 compounds was isolated and identified, including 16 new compounds. Antifungal test showed that some of the isolated steroids had inhibitory activity on Cryptococcus neoformans.
Chapter 3. A detailed phytochemical investigation on Phyllanthus urinaria was carried out, which led to the isolation of 15 phenolic compounds (1-15). Among them the structure of repandinin B (1) is represented by total assignment of NMR data. With the examination of the DPPH assay and inhibitory activity on tyrosinase, most of the isolated compounds showed stronger antioxidant activity than that of the positive control.
In addition, a HPLC fingerprint analysis method was established and used in the analysis of the P. urinaria. A quantitative study of this herb was concluded. A new method for large scale isolation and purification of corilagin from plant resources was invented, which was low-cost and suitable for industrial use. Based on this study, a new standard of P. urinaria was proposed.
Chapter 4. Review
The advances including the medicinal plant resources and biological activities of genus Gentiana were reviewed.
Based on above research work, three papers have been published, two papers have been accepted, one paper has been submitted, and another six are in preparation. Moreover, two patents were published.|