Characterization And Biosynthetic Mechanism Of Azoxymycins

Azoxy compounds have been long used as dyes, reducing agents, chemical stabilizers, polymerization inhibitors, therapeutic agents and explosive materials. Recently, the light-controllable liquid crystalline properties of aromatic azoxy compounds have attracted considerable attention. Materials synthesized from these compounds have light-controllable properties and are used in liquid crystal laser systems and devices capable of converting light energy to macroscopic motion. In such functions, a light-induced switch between the trans to cis configurations of the azoxy bond is utilized. To date, only a few natural azoxy compounds have been reported, and only a few biosynthetic studies conducted. The bio synthetic mechanism of the azoxy bond has likewise not yet been fully elucidated. Discovering the biosynthesis of these important compounds, especially the synthetic mechanism of the azoxy bond, might facilitate the biological or semi-biological synthesis of similar liquid crystalline materials.Streptomyces chattanoogensis L10, an industrial natamycin producing strain, has been observed to produce some unidentified yellow pigments. In this research, three aromatic azoxy products, azoxymycins A, B and C, are isolated from S chattanoogensis L10. Their molecular formulas are calculated and confirmed by the isotope replace experiments. The structures of azoxymycins A and B were elucidated using 1D and 2D NMR. Due to low solubility, the clear NMR spectra of azoxymycin C are not determined. Thus the structure of azoxymycin C is elucidated by MS, UV absorption and acid hydrolysis experiments.While the biosynthesis of azoxy bond has remained unclear, S. chattanoogensis L10 might provide a suitable model to elucidate this process. Based on the identified structures of azoxymycins and bio informatics analysis, the biosynthetic gene cluster are screened from the sequenced genome of S. chattanoogensis L10. Further gene deletion experiments strongly support the proposed gene cluster and the biosynthetic pathways. Besides, a special N-oxidase, AzoC, is proved to be associated with the key azoxy bond formation in the biosynthesis of azoxymycins. The biosynthetic study of azoxymycins might address the mystery of azoxy bond biosynthesis.The bioactivity and chemical activities are evaluated in this thesis. Azoxymycins show no inhibition to the tested bacteria, fungus and cell lines at the cellullar level. However, they have Caspase-3 and PTP1B inhibition activity at the molecular level. Chemically, all three azoxymycins exhibit light-induced isomerization, which is the base of the aromatic azoxy compounds’ liquid crystalline property.In conclusion, three novel aromatic azoxy compounds, azoxymycins A, B and C, are isolated and identified from S. chattanoogensis L10, their biosynthetic pathways are elucidated, and their biological and chemical activities are studied as well.