Studies On Chemical Constituents Of Hypericum Chinense L.

Staphylococcus aureus is a common organism that is cited as being a major hospital-acquired pathogen emerging serious drug resistance. It is urgent to develop new agents to combat multidrug-resistant (MDR) bacteria. We have obtained an active xanthone from Hypericum sampsonii, which exhibited promising activity against a multidrug-resistant strain of S. aureus. As part of our ongoing research to discover new classes of drugs or leads against MDR bacteria, we continued the phytochemical research in the plants of Hypericum genus.Hypericum chinense L., is a plant of Hypericum genus (Hypericeae). This semi-evergreen herb is widely spread as a landscape plant in many provinces of China. Besides, it has long been used by the folk people as traditional Chinese medicine to treat depression, rheumatism, cough, trauma, etc. The extract of H. chinense L. having been studied by many researchers indicated various pharmacological actions such as antibacterial, antiviral, free radical scavenging, tyrosinase inhibitory and cytotoxic activities. Its chemical constituents were mainly reported by the Japanese researchers. So far to our knowledge, there have been 74 compounds discovered from this herb, most of which are xanthones. Other types include phloroglucinols, spiro-lactones, etc. These compounds have shown a broad range of pharmacological functions which are responsible for those exhibited by the extract. To investigate more molecules that may possess important pharmacological actions, or may be new structure skeletons, this thesis has made further effort trying to demonstrate the diversity of H.chinense L. of both its chemical structures and biological activities.In this phytochemical research,15 compounds have been isolated from H. chinense L. from the ethyl acetate extract of its roots, leaves and fruits, respectively (Figure 1). Spectroscopic analysis was used to elucidate all the structures. Six of them are identified as new compounds (7,9-11,13,14), another known four (4,8,12,15) are first reported from this species.The compounds were examined for the anti-MDR bacteria activity. Among them,11 and 12 showed promising inhibitory activity with the MIC values at 2 and 4μg/mL, respectively. While the MIC value of the positive control antibiotic norfloxacin was 16-32μg/mL.This thesis contains three chapters. Chapter 1 is the preface, in which the traditional medical use of H. chinense L. was discussed, together with the present research situation of Hypericum genus and H. chinense L. species in the aspects of resources, phytochemistry, and pharmacology. In chapter 2, the isolation, purification and elucidation of the compounds obtained from the roots and leaves of H. chinense L., along with the results of bioactive research of these compounds, were discussed. The related experimental material and methods as well as the physical and chemical data of the compounds were reported in detail in chapter 3.