Primary bile acids (PBAs)

Only about 5% of primary bile acids escape into the large intestine, where they are modified by gut microbiota into Secondary bile salts / Secondary bile acids (SBAs), such as the highly toxic deoxycholic acid (DCA), lithocholic acid (LCA), and ursodeoxycholic acid (UDCA) through a multistep process that involves deconjugation and dehydroxylation. This modification is facilitated by bacterial bile salt hydrolases and 7-alfa-dehydroxylase
Schubert et al. 2017 Immunological Reviews 279: 23-35
Hanafi et al. 2018 Biomolecules 8: 159
Sinha et al. 2020 Cell Host & Microbe 27: 659-670
Xie et al. 2021a

Cholic acid (CA) and chenodeoxycholic acid (CDCA) are the two most common primary bile acids conjugated to either taurine or glycine and the most common primary BAs in humans.
Hanafi et al. 2018 Biomolecules 8: 159
Taylor et al. 2022 Drug Metab Dispos 50: 456-467

Primary bile acids are made in hepatocytes of the liver and are mainly conjugated with glycine or taurine in humans (>99% conjugated = primary bile salts) and rodents. After their transport via BSEP they are stored in the [gallbladder] prior to their secretion into the proximal small intestine (?id=89a16211-4562-4d16-9dab-a3682da71322&linkText=gallbladder)
Hofmann 2009 Hepatology 49: 1403-18
Li & Chiang 2012 J. Lipids 2012: 754067
Sauerbruch et al. 2021 Front. Physiol. 12:718783

see also:
Bile acids / Bile salts
Bile Acids / Bile Salts & Enterohepatic circulation