Glycyrrhetinic acid (GA), the major bioactive pentacyclic triterpene aglycone of licorice root, was known to play a vital role in anti-ulcer, anti-depressant, anti-inflammatory, and anti-allergic. In this study, we semi-synthesized five GA derivatives by a series of chemical reactions. They were selected as substrates for the biotransformation and yielded thirteen metabolites by Bacillus subtilis ATCC 6633 and Bacillus megaterium CGMCC 1.1741. Their structures were identified on the basis of extensive spectroscopic methods and nine of them were found for the first time. Two main types of reactions, regio- and stereo-selective hydroxylation and glycosylation, especially in the unactivated C-H bonds including C-11, C-19 and C-27, were observed in the biotransformation process, which greatly expand the chemical diversities of GA derivatives. All compounds were tested for their inhibitory effects on nitric oxide (NO) generation in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. Among them, olean-12-ene-3β,7β,15α,19α,30-pentol (16) and olean-12-ene-3β,7β,15α,27,30-pentol (17) showed significant inhibitory effect with IC50 values of 0.64 and 0.07 μM, respectively.

中文翻译：

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枯草芽孢杆菌ATCC 6633和巨大芽孢杆菌CGMCC 1.1741对甘草次酸衍生物的微生物转化。

甘草次酸（GA）是甘草根的主要生物活性五环三萜糖苷配基，已知在抗溃疡，抗抑郁，抗炎和抗过敏方面起着至关重要的作用。在这项研究中，我们通过一系列化学反应半合成了五种GA衍生物。它们被选作生物转化的底物，并被枯草芽孢杆菌ATCC 6633和巨大芽孢杆菌CGMCC 1.1741产生13种代谢物。根据广泛的光谱学方法鉴定了它们的结构，并且首次发现了其中的九种。在生物转化过程中观察到两种主要类型的反应，区域和立体选择性羟基化和糖基化，特别是在未激活的CH键中，包括C-11，C-19和C-27，大大扩展了GA的化学多样性衍生品。测试了所有化合物对脂多糖（LPS）刺激的RAW 264.7细胞中一氧化氮（NO）生成的抑制作用。其中，olean-12-ene-3β，7β，15α，19α，30-pentol（16）和olean-12-ene-3β，7β，15α，27,30-pentol（17）对IC50表现出明显的抑制作用值分别为0.64和0.07μM。