Preparation Of Active Sesquiterpene Lactone Glucosides From Ixeris Sonchifia (Bge.) Hance And Studies On Their Biotransformation

Ixeris sonchifolia (Bge.) Hance is an annual composite plant which is abundantly distributed throughout the northeastern China. Among the complex chemical constituents of I. sonchifolia, sesquiterpene lactones are major ingredients with patent biological activity.In our study of the bioactive constituents of I. sonchifolia, two sesquiterpene lactone glucosides(including lactone glucoside I and II) were isolated with chromatograghy in porous resin, silica gel and preparative HPLC etc. The structures of them were elucidated by analyses of spectra and comparation with published data. Lactone glucoside I was identified as 1(10), 3,11(13) -guaiatriene-12,6-olide-2-one-3-O-glucopyranoside, and lactone glucoside II was identified as 1(10), 3-guaiadiene-12, 6-olide-2-one-3-O-glucopyranoside. Preparative method of the combination of these two sesquiterpene lactone glucosides were established by optimizing the experiment conditions. The content of lactone glucoside I and II in the native plant was measured with HPLC and the technology consideration was also carried out.Previously, A. versicolor D-1 was reported to have the ability to reduce the conjugatedγ,δ-double bond of the unsaturated lactone by our group. In this study, A. versicolor D-1 was tested for the ability to transform the sesquiterpene lactone glucosides (including lactone glucoside I and II) as substrates. It was found that the results of biotransformation were different by using growing culture and resting culture. HGD was isolated from the broth of growing culture, while lactone glucoside II was isolated from the broth of resting culture. The result indicated that in the process of the biotransformation of growing culture,β-glucosidic bond was hydrolysed as while as theα,β-double bond outside the unsaturated lactone ring was reduced. However, in the process of the biotransformation of resting culture, only theα,β-double bond was reduced.Otherwise, by the determination of the reductase using HPLC analyses, it was further confirmed that the reduction of theα,β-double bond outside the unsaturated lactone ring could be catalyzed by A. versicolor D-1. It is also indicated that lactone glucoside I reductase is an intracellular soluble protein in cytoplasm. Single-factor experiments were carried out to evaluate the effects of initial pH, temperature, initial concentration of substrate and addition stage of substrate on reduction of I. sonchifolia lactone glucoside I by resting culture of A. versicolor D-1. The results showed that the reduction activity of the resting culture was at maxium after incubation of gh in pH 7.0 buffer containing substrate (0.2mg/mL) at 28℃. Dynamic curve showed that in optimized condition, A. versicolor D-1 reduced lactone glucoside I in over 95% yield after incubation of 8h.