Studies On Chemical Constituents Of Arnebia Euchroma And The Activity Against Multidrug-resistant Bacteria

Arnebia euchroma, a perennial herb belonging to Boraginaceae, has long been used as traditional Chinese medicine for its various pharmacological actions indicated by plenty of researches, such as antibacterial, anti-inflammatory, antitumor, antifungal, antiviral, anti-HIV, and contraceptive actions. In a search for active constituents, several chemical constituents including naphthoquinones, monoterpenyl phenols and benzoquinones, phenylpropanoids, terpenes and alkaloids have been found in A. euchroma. It has been discovered that naphthoquinones, the dominant chemical constituent of A. euchroma, are responsible for its therapeutic efficacy.Staphylococcus aureus is a severe bacterial pathogen which has been commonly considered as a major pathogen causing hospital-acquired infection. In recent years, it has been resistant to a majority of antibiotics. As a result, it is urgent to find new agents to inhibit the multidrug-resistant bacteria.Previously, we have evaluated the activity of the roots of Arnebia euchroma against the NorA overexpressing MDR S. aureus strain SA1199B. Encouraged by its good result, we carried out the Phytochemical research on Arnebia euchroma.On bioassay guided 8 compounds have been isolated from fractionation of ethanol extract for roots of Arnebia euchroma, including one known compoundβ,β-dimethylacrylalkannin (1) which belongs to naphthoquinone monomers. Compounds 2-8 are 7 blue solids identified as naphthoquinone dimers that were first separated from the plants. The structures of compound 2 (AE02-15-15), 3 (AE02-15-2), 4 (AE02-15-7), 5 (AE02-15-8) which are four new compounds have been determined.The activity tests on compounds and mixtures isolated from A. euchroma indicate the naphthoquinone monomers have excellent resistance againest various bacteria.GC-MS and Silica Column Chromatography were used to investigate the hydrophobic constituents of A. euchroma. With the experiments of AE and AEZ from different sources, 11 and 22 compounds have been identified, including 5 common compounds that were the main components. AE01-1, the hydrophobic constituents of AE, has 2 naphthoquinones, while AEZ01-1, the hydrophobic constituents of AEZ, has only lipid compounds.This thesis is consisted of three chapters. The first chapter is the preface, in which the research background of antimicrobial resistance in MDR-MRSA was discussed, together with the present research situation of Arnebia genus and A. euchroma species in the aspects of resources, phytochemistry, and pharmacology. In chapter 2, the isolation, purification and elucidation of the compounds obtained from the roots of A. euchroma were discussed, along with the results of activity tests against drug-resistant bacteria, and a study on hydrophobic constituents of A. euchroma. The related experimental material and methods as well as the physical and chemical data of the compounds were reported in chapter 3.