Structure Determination of Bioactive Metabolites from Marine-Derived Fungi and Simultaneous Analysis of Herbal Medicines by HPLC-DAD-ELSD-MS

Abstract

Part A. Structure Determination of Bioactive Metabolites from Marine-Derived Fungi Marine natural products have been proven to be a prolific source of novel therapeutic agents that have demonstrated significant activities in various pathological conditions including cancer, viral infection, inflammation, analgesia, and immune modulation. The marine-derived fungi is one of the three dominated phylogenetic groups, have shown great diversity of their secondary metabolites and a wide range novel secondary metabolites have been isolated since 1980s. Marine-derived fungi alone have produced more than 400 novel compounds, of which several have exhibited potent and diverse bioactivities. The purpose of this study is to investigate new marine natural products from marine-derived fungi and study their biological activities. During the course of searching for bioactive metabolites from marine-derived fungi, two strains Penicillium sp. and Aspergillus sp. were selected for chemical investigation based on LC-ESIMS analysis and bioassay screening of the crude extracts. Secondary metabolites from the selected fungi were isolated and structure determination based on 1D, 2D NMR, and IR, UV, OR and MS. As a result, 9 novel compounds and 9 known compounds were structurally determined using integrated spectroscopic analysis and chemical approaches. These compounds belonged to various structural classes: meroterpenoids, alkaloids, anthroquinones, and lipopeptides. The biological activities of the isolated compounds were studied on various bioactivity tests: cytotoxicity, antimicrobial activities, inhibition against the enzymes isocitrate lyase (ICL), sortase A (SrtA) and Na+/K+-ATPase, and quinone reductase. Structure-activity relationships were also deduced. Part B. Simultaneous Analysis of Herbal Medicines by HPLC-DAD-ELSD-MS Traditional herbal medicines have been practiced to maintain health and treat diseases especially in the Asia communities for more than 2,000 years. Increment of worldwide attention and concomitant pharmaceutical research has made it essential to carry out the quality control measurement for the herbal medicines. However, serious hindrance has been attributed to the lack of recognition and regulation of professions, qualified practitioners, quality-controlled herbal medicines, and evidence-based clinical studies. Thus it is urgently needed to establish a comprehensive qualified evaluation method that could accurately reflect the quality of herbal medicines. The purpose of this study is developing simultaneous analysis methods of bioactive compounds in herbal medicines. Two herbal medicines, which are Kalopanacis Cortex and Semen Ziziphus jujuba were subjected to the current study. In herbal medicines, it is hard to consider that single or a few compounds would determine the overall pharmacological activities. Rather, it is more likely that multiple compounds act simultaneously and attribute to the therapeutic function of the herbal medicine. For this reason, most bioactive metabolite in the selected herbal medicines were analyzed and determined. In particular, three phenolics and nine hedergenin saponins were selected for the analysis of Kalopanacis Cortex. Moreover, one alkaloid, five flavonoid saponins and three jujuboside saponins from Semen Ziziphus jujuba were also analyzed. The methods based on HPLC-DAD-ELSD-MS was established for the quantitative and qualitative analysis of a selected folk medicine. Various validation parameters, such as linearity, limit of detection, limit of quantification, recovery, accuracy, and precision, were successfully obtained. In addition, the efficiencies of diverse extraction methods were compared for the development of a standard analytic method. The verified methods were successfully applied to the quantitative determination of representative metabolites in commercial samples from Korea, Myanmar and China.