Colonization Of Isoflavone Biotransforming Bacterium In The Intestinal Tract Of ICR Mice

Soybean isoflavones (SI) are secondary metabolites produced in the growing process of soybeans and some other leguminous plants. It is known that SI are of different kinds of physiological bioactivities, such as antioxidant, antitumor, prevention of cardiovascular and cerebrovascular diseases, prevention of osteoporosis etc. After being absorbed SI can be degraded into different metabolites, including dihydrodaidzein (DHD), dihydrogenistein (DHG), equol and O-desmethylangolensin (O-Dma) by gastrointestinal microflora. Based on medical research, the metabolites of daidzein, such as equol and DHD, showed stronger and wider biological activities than that of their parent compound daidzein. Due to the influences of different eating habits, diseases, the use of antibiotics and different kinds of pressure, different animals or different varieties or individuals belonging to the same species are of different SI biotransforming capacity. In order to make those animals which do not have the capacity to biotransform SI to obtain SI biotransforming ability, we tried for the first time to plant the isoflavone biotransforming bacterium in the intestinal tract of ICR mice. In this study, anaerobic bovine rumen gastric bacterium strain Niu-O16 (AY263505) capable of biotransforming daidzein to DHD was used. In order to protect bacterium strain Niu-O16 from being damaged by gastric acid in the stomach of experimental ICR mice or oxygen in the atmosphere, strain Niu-O16 were wrapped into microcapsules before intragastric administration.In this study, ICR mice were chosen as the experimental animals because of their small body sizes and being fed exactly the same food. According to our previous study, different ICR mice showed consistent and steady SI biotransforming ability. That is the main reason why ICR mice were used as the experimental animals. Bacterium strain Niu-O16 can convert daidzein to DHD, however, ICR mice also has the ability to convert daidzein to DHD. Therefore we screened different varieties of antibiotics and chose a suitable one to feed healthy ICR mice. We obtained those ICR mice which have totally lost the ability to biotransform SI through intragastric administration after being treated with suitable antibiotic, the ICR mice of which were called experimental mice model. The results indicated that ICR mice completely lost the ability to transform SI and did not show any adverse symptoms after being fed azithromycin (AZI) continuously for one week through intragastric administration, the concentration of which was 420mg/mL. The ICR mice which have been fed AZI for one week recovered their capacity to biostransform SI after about 20 d since they were fed AZI. We fed the ICR mice model with microencapsulated strain Niu-O16 continously for 5 days. One week later, we began to detect the biotransforming capacity of the microflora of the ICR mice model. Based on HPLC detection profiles, the microflora of the ICR mice model, which had been fed the microcapsules of strain Niu-O16 for 5 d, could convert daidzein to DHD. However, we did not detect any similar biotransforming activity from the controls, i.e. those ICR mice models which were not fed strain Niu-O16. Our results indicated that bovine rumen bacterium strain Niu-O16 coated in the microcapsule was able to colonize in the intestinal tract of the ICR mice model.