The biotransformation of digitoxin and some of its derivatives extracted from Digitalis lanata by Streptomyces isolated species was investigated. Cultures of a Streptomyces strain designated EUSA2003B, isolated from an Egyptian soil sample, efficiently induced selective 12β-hydroxylation of the steroid aglycone of digitoxin (DT) and its α-acetyl and β-methyl derivatives. The transformation reaction was performed within a 5-day fermentation process, products were isolated and their aglycone moiety was obtained by acid hydrolysis and their structures were elucidated by 13C and 1H NMR. The biotransformation resulted mainly digoxin (DG, ∼87%), meanwhile, digoxigenone (DGON, ∼7.0%) was also afforded as a side product. The present study revealed that: 1-Streptomyces isolate EUSA2003B harbors its specific 12β-hydroxlase and has the capability to transform DT and it's α-acetyl and β-methyl derivatives into their corresponding digoxins at reasonable yields. 2-The minor structural differences in the trisaccharide side chain seemed ineffective on the transformational capability of this organism. 3-The Streptomyces might also possess a specific glycosidase that splits the saccharidic side chain beside another dehydrogenase that oxidizes C3 at the steroid nucleus into its ketone form (DGON).
从毛花洋地黄中提取的
地高辛及其部分衍
生物,通过分离的链霉菌种进行
生物转化研究。从埃及土壤样本中分离得到的链霉菌株EU
SA2003B,能够高效诱发
地高辛(DT)及其α-乙酰和β-甲基衍
生物的甾体苷元发生选择性的12β-羟基化。该转化反应在5天的发酵过程中进行,产物通过酸
水解分离并得到其苷元部分,其结构通过13C和1H核磁共振波谱技术鉴定。
生物转化结果主要产生的是
地高辛(DG,约87%),同时也有少量
地高辛酮(DGON,约7.0%)作为副产品产生。本研究揭示:1- 链霉菌分离株EU
SA2003B含有特异的12β-羟化酶,具有将
地高辛及其α-乙酰和β-甲基衍
生物转化为相应
地高辛的能力,产量合理。2- 三糖侧链的细微结构差异对该
生物的转化能力似乎没有影响。3- 链霉菌可能还具有特定的糖苷酶,能够切割糖侧链,以及另一种将甾体核C3位氧化为其酮形式的脱氢酶(形成DGON)。