Assalam 3alaykum Khalid, The chemistry of TUCA shows that it is a hydrophilic bile acid because it has many polar groups. There is no problem at all for such compound to cross the blood brain barrier because of its small size and hydrophilicity. It has been reported also elsewhere: Recent preclinical studies have demonstrated that TUCA is endowed with antioxidant, antiapoptotic and neuroprotective activities. In particular, TUDCA can cross the blood-brain-barrier and has been shown to exert a significant therapeutic effect in a model of HD mice.

Tauroursodeoxycholic acid (TUDCA) is a hydrophilic bile acid that is normally produced endogenously in humans at very low levels. TUDCA is synthesized in the liver by conjugation of taurine to ursodeoxycholic acid (UDCA), which is commonly used as a bile acid replacement therapy for the treatment of certain cholestatic syndromes.

Second Part of YOUR Question: My understanding SFO laks NORMAL BBB. See the details in this link: http://en.wikipedia.org/wiki/Circumventricular_organs