Investigation of baicalin, baicalein and low-dose sulfasalazine for orocecal transit time determination in saliva and plasma

The application of high-dose sulfasalazine (≥ 500 mg) followed by plasma or salivary sampling represents an established method for orocecal transit time determination. In the present study, we aimed to establish an alternative procedure. For this, we investigated. (1) whether the onset of baicalin or its aglycon baicalein in plasma or saliva after oral application correlated with the onset of sulfapyridine in plasma and. (2) whether the onset of sulfapyridine in saliva correlated with its onset in plasma. following the oral ingestion of low–dose sulfasalazine (50 mg) and 400 mg baicalin. Furthermore, in a second study arm 400 mg baicalein were applied together with 50 mg sulfasalazine to enhance the understanding of the oral pharmacokinetics and conversion of baicalin and baicalein. The oral application of baicalein led to an onset of plasma concentration that was substantially earlier than that of sulfapyridine. In contrast, the plasma appearance times of baicalin after oral baicalin administration was not statistically significant different from sulfapyridine plasma appearance time. However, baicalin was not secreted into saliva. Low–dose sulfasalazine proved to be a reliable salivary marker for the determination of the orocecal transit time, like already reported for high dosages. The correlation between plasma and salivary concentrations and appearance times was excellent. However, there was a statistically significant difference between sulfapyridine plasma and saliva appearance time, mainly attributable to the lower salivary sulfapyridine concentrations taking slightly more time to reach the threshold defined as appearance. Hence, it is necessary to consider the generally lower salivary sulfapyridine concentrations in appearance time determination. As this procedure only uses minimal dosages (1/10 of the lowest therapeutic dosage), the risk for side effects is reduced. Taking into consideration that the possibility for saliva sampling enables a non–invasive procedure without the need for specialized personal, this approach represents an easy to use method for studies investigating orocecal transit times.