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World J Gastroenterol. Mar 28, 2009; 15(12): 1518-1523
Published online Mar 28, 2009. doi: 10.3748/wjg.15.1518
Biotransformation of aesculin by human gut bacteria and identification of its metabolites in rat urine
Wei-Jun Ding, Yun Deng, Hao Feng, Wei-Wei Liu, Rong Hu, Xiang Li, Zhe-Ming Gu, Xiao-Ping Dong
Wei-Jun Ding, Yun Deng, Wei-Wei Liu, Rong Hu, Xiang Li, Xiao-Ping Dong, Chengdu University of Traditional Chinese Medicine, Chengdu 610075, Sichuan Province, China
Hao Feng, Zhe-Ming Gu, XenoBiotic Laboratories, Inc. 107 Morgan Lane. Plainsboro, NJ 08536, United States
Author contributions: Ding WJ, Dong XP, Gu ZM and Deng Y designed the research; Ding WJ, Deng Y, Liu WW, Feng H, Hu R and Li X performed the research; Hu R, Deng Y and Feng H analyzed the data; Ding WJ, Gu ZM and Deng Y wrote the paper.
Correspondence to: Dr. Wei-Jun Ding, Laboratory of Microbiology, Chengdu University of Traditional Chinese Medicine, 37#, Shier Qiao Street, Chengdu 610075, Sichuan Province, China.
Telephone: +86-28-61800219
Fax: +86-28-87763471
Received: January 14, 2009
Revised: February 27, 2009
Accepted: March 6, 2009
Published online: March 28, 2009

AIM: To observe the biotransformation process of a Chinese compound, aesculin, by human gut bacteria, and to identify its metabolites in rat urine.

METHODS: Representative human gut bacteria were collected from 20 healthy volunteers, and then utilized in vitro to biotransform aesculin under anaerobic conditions. At 0, 2, 4, 8, 12, 16, 24, 48 and 72 h post-incubation, 10 mL of culture medium was collected. Metabolites of aesculin were extracted 3 × from rat urine with methanol and analyzed by HPLC. For in vivo metabolite analysis, aesculetin (100 mg/kg) was administered to rats via stomach gavage, rat urine was collected from 6 to 48 h post-administration, and metabolite analysis was performed by LC/ESI-MS and MS/MS in the positive and negative modes.

RESULTS: Human gut bacteria could completely convert aesculin into aesculetin in vitro. The biotransformation process occurred from 8 to 24 h post-incubation, with its highest activity was seen from 8 to 12 h. The in vitro process was much slower than the in vivo process. In contrast to the in vitro model, six aesculetin metabolites were identified in rat urine, including 6-hydroxy-7-gluco-coumarin (M1), 6-hydroxy-7-sulf-coumarin (M2), 6, 7-di-gluco-coumarin (M3), 6-glc-7-gluco-coumarin (M4), 6-O-methyl-7-gluco-coumarin (M5) and 6-O-methyl-7-sulf-coumarin (M6). Of which, M2 and M6 were novel metabolites.

CONCLUSION: Aesculin can be transferred into aesculetin by human gut bacteria and is further modified by the host in vivo. The diverse metabolites of aesculin may explain its pleiotropic pharmaceutical effects.

Keywords: Aesculin, Biotransformation, Human gut bacteria, Rat urine, Sulfated derivatives, LC/ESI-MS, Aseculetin