OBJECTIVE

2

To investigate the absorption characteristics and tissue distribution of silybin （Sy） nanocrystals prepared by two methods in different intestinal segments of rats.

METHODS

2

Sy nanocrystals （i.e. Sy-NS-G and Sy-NS-F） with comparable particle sizes were prepared using high-pressure homogenization and anti-solvent precipitation methods， respectively. Rats were randomly divided into three groups： Sy raw drug group， Sy-NS-G group， and Sy-NS-F group. Each group was further divided into three subgroups with low， medium， and high （60， 120， 180 μg/mL） mass concentrations （calculated based on Sy）， with 3 rats in each subgroup. The absorption rate constant （

K

a

） and apparent absorption coefficient （

P

app

） of Sy raw drug， Sy-NS-G and Sy-NS-F in different intestinal segments were investigated by using the

in vivo

one-way intestinal perfusion experiment. Additionally， the rats were divided into three groups: Sy raw drug group， Sy-NS-G group， and Sy-NS-F group， with 20 rats in each group. Rats in each group were administered a single intragastric dose of 50 mg/kg （calculated based on Sy）. They were sacrificed at 0.3， 1， 4， 10， and 24 hours post-administration respectively， to investigate the tissue distribution of Sy raw drug， Sy-NS-G， and Sy-NS-F in the heart， liver， spleen， lungs， kidneys， brain and intestines.

RESULTS

2

In duodenum and jejunum， the

K

a

and

P

app

of the nanocrystals prepared by the two methods remained unchanged with the increase

of Sy concentration， and there was no significant difference （

P

＞0.05）； the absorption of Sy-NS-F in the duodenum was greater than that of Sy-NS-G； the absorption sites of Sy-NS-G and Sy raw drug were mainly in the ileum， while those of Sy-NS-F were mainly in the duodenum and ileum. The concentrations of Sy-NS-G and Sy-NS-F in different tissues of rats were different； Sy-NS-G peaked in most tissues at 1 h， and the distribution concentration was as follows： intestine＞spleen＞heart＞lungs＞liver≈brain＞kidneys. Sy-NS-F reached its peak at 1 h， and the distribution concentration was in the order of intestine＞spleen＞kidney＞lung＞heart≈liver＞brain.

CONCLUSIONS

2

The absorption mode of Sy nanocrystals in the duodenum and ileum is mainly passive diffusion. In the duodenum， the absorption of Sy-NS-F is greater than that of Sy-NS-G； there are significant differences in the tissue distribution of Sy-NS-G and Sy-NS-F in rats.