| The soil Actinomycete, Streptomyces luteogriseus strain 670, showed to produce secondary metabolites with the remarkably inhibitory activities against several saccharide hydrolases, such as sucrose invertase and ct-amylase. The effective fraction, WC670, was extracted and isolated from the culture filtrate of S. luteogriseus, which found to be a very complex mixture of aminooligosaccharides, possibly containing the known hypoglycemic agents, isovalertatins. An agricultural trial proved that WC670 could significantly increase the sucrose output of sugarbeet. Therefore, WC670 might be further developed in agriculture and in treating diabetes and obesity in medicine. The aims of this study were to interpret the chemical composition of WC670 by applying the advanced techniques of chemical screening and structural characterization, and to under- stand the biotransformation pattern of aminooligosaccharides by microorganisms and in rats. 1. Structural reinvestigation of the six known isovalertatins A preliminary LC/ESI-MS analysis confirmed that the WC670 contains all of the six known isovalertatins. However, when verifying their structures, we found several inconsistencies in the spectroscopic data. This encouraged us to reinvestigate their structures. B The WC670 sample was dissolved in water and used for separation by means of semi- preparative RP-HPLC on a Spheisorb C3 column where the mobile phase was ACN-1.5 mmol/L aqueous ammonia with UV detection at 206 nm, which yielded the six oligomers. Careful inspections of the CII) spectra and the hydrolysis results catalyzed by the glucoamylase led to the confirmation of the composed units and their linkage sequence. And, extensive analyses of the NMR data and the color reaction results made the revisions of their linkage positions and glycosidic bond configurations. Thus, their chemical structures were finally established. The names for the six oligomers were redesignated isovalertatins M03, M13, M23, D03, D13, and D23, respectively. 2. Compositional interpretation of the secondary metabolits produced by S. luteogrisew The ESI-MS analysis of WC670 sample illustrated the complexicity of the mixture. Besides the six known isovalertatins, there existed much more homologues with different numbers of glucose and pseudoU-isaccharide units, and variable linkage sequences and an esterized side chain. The combination of these changeable structural factors made the expectation of the possible compositions. And, by exploiting the summarized positive ESI-MS fragmentation patterns for isovalertatins, the miz values for the protonated molecular ions of the desired components and their potential CII) product ions derived from the single bond cleavages could also be predicted. Thus, by using a unique and active LCIESI-MSIMS procedure of analyzing - lv - ABSTRACT V these desired components through the SRM chromatograms and the corresponding CID spectra. we had totally identified the presence of 138 components. Of all the detected compositions, six isovalertatins are the known. And among the 132 newly characterized components, eleven oligomers, isovalertatins M33, D33, D43, 103, 113, butytatins M03, M13, and isohexanytatins M33, M43, D23, D43 had been prepared by RP-HIPLC methods. Their determined structures were a...
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