Insight into the secret of how indigo naturalis works: in vitro and in vivo validation of the critical role of bile­

Abstract

<jats:title>Abstract</jats:title> <jats:p><jats:bold>Background:</jats:bold> Indigo Naturalis (IN) has positive therapeutic effects on cancer, leukemia, colitis, psoriasis, fever and other diseases that seriously endanger human health. It contains 10% organic matter and 90% inorganic matter with extremely hydrophobic. However, the clinical usage of IN is mainly by oral administration. And how IN exerts its effect after oral administration is still a secret remained to be discovered. <jats:bold>Methods: </jats:bold>In this study, in <jats:italic>vitro </jats:italic>and in<jats:italic> vivo</jats:italic> experiments were performed. The <jats:italic>vitro</jats:italic> experiments simulate the in <jats:italic>vivo</jats:italic> process of IN by different digestive fluid and the effects of a small amount and normal amount of bile on the organic and inorganic matter release of IN were compared. And the surface morphology and elements of IN in different solutions were also observed. In addition, 2, 4-dinitrophenol-induced fever rat model was also used to investigate the intervention effect of IN on the fever of normal rats and bile duct ligation rats. <jats:bold>Results:</jats:bold> It was found that bile plays an important role in promoting the carrier dissolution and release of inorganic and organic matters from IN. And IN had better antipyretic effect on normal rats than on bile duct ligation rats, which further proved that bile is important to the curative effect of IN. <jats:bold>Conclusions:</jats:bold> The results indicate that the calcium carbonate carrier translates into a slightly soluble state in the acidic simulated gastric fluid. And a small amount of organic matter was released from the calcium carbonate carrier. When IN entering the simulated intestinal fluid which mixed with bile, a large amount of carrier dissolved, and organic substances such as indirubin dissolved out in large quantities, thereby being absorbed into the blood and exerting therapeutic effect. The above findings have certain guiding significance for the clinical application of IN. For patients with insufficient bile secretion such as cholangiotomy, oral IN may have poor curative effect and even doesn't work.</jats:p>