Abstract:

[Objective] The present study aimed to evaluate the controlled-releasing performance of benzoic acid in different forms in vitro and in vivo. [Method] This study consisted of two parts, an in vitro dissolution test and an in vivo controlled-release test. ① In vitro dissolution test: Artificial gastric liquid and artificial intestinal liquid was prepared, with ordinary benzoic acid or controlled-release benzoic acid in the 200 mesh baskets. Samples were taken from the dissolution meter at 1, 2 h for artificial gastric liquid or 1, 2, 3 and 4 h for artificial intestinal liquid. High-performance liquid chromatography （HPLC） was used to determine the content of benzoic acid, and the dissolution rate and retention rate were calculated. ② In vivo controlled-release test: A total of 36 healthy Qingyuanma broilers with similar weights were selected and assigned into 3 groups after pre-feeding, with 12 individuals in each group. After morning feeding, the broilers in control group, ordinary benzoic acid group and controlled-release benzoic acid group were immediately fed with pure flour pills, flour pills containing 0.1% ordinary benzoic acid and flour pills containing 0.1% controlled-release benzoic acid, respectively. On 0, 1, 2 and 4 h after given the pills, three broilers were chosen from each group, respectively. The broilers were slaughtered and the contents in each segment of gastrointestinal tracts were taken. The concentration of benzoic acid in the gastrointestinal contents of broilers were assessed by HPLC. [Result]① In vitro dissolution test: In artificial gastric liquid for 1 h, the retention rate of controlled-release benzoic acid was 3.45 times that of ordinary benzoic acid. In artificial gastric liquid for 2 h, ordinary benzoic acid was not detected, while the retention rate of controlled-release benzoic acid was 56.18%. The retention rate of controlled-release benzoic acid was 40.10% in the artificial intestinal fluid for 4 h, while ordinary benzoic acid was not detected at 1 h. ② In vivo controlled release test: The concentration of benzoic acid in glandular stomach and muscular stomach of the controlled-release benzoic acid group was 5.46 times of the ordinary benzoic acid group 1 h post ingestion of the pills, exhibiting a significant （P<0.05） difference. The concentration of benzoic acid in contents of jejunum, ileum and cecum of the controlled-release benzoic acid group 2 h post ingestion of the pills was 1.61, 2.43 and 1.95 times of the ordinary benzoic acid group, respectively, all exhibiting significant （P<0.05） differences. The concentration of benzoic acid in ileum contents of the controlled-release benzoic acid group was 6.68 times of the ordinary benzoic acid group 4 h post ingestion of the pills, exhibiting a significant （P<0.05） difference. [Conclusion] Both in vitro dissolution test and in vivo controlled-release test showed that the controlled-release benzoic acid prepared by coating treatment had a high gastric pass rate and was able to slowly release into the entire intestinal tract after entering to achieve long-term antibacterial effect.

Key words: benzoic acid, dissolution rate, controlled-release, artificial simulation