4. SPECIES DIFFERENCES IN BILE SALTS
209
acid is 3a:,7a!,12a-trihydroxycholanic, whose allo (5«) epimer also occurs
(37).
Hyocholic acid (VI) from pig bile (37a) is 3a,6a,7a:-trihydroxycholanic (38-40).
CH 3
I
3
HO CH-CH 2 -CH 2 -COOH
HO"
(V)
^OH
Two acids recently found in rat bile are 3afiß,7a- and Saßß,7ß-trihydroxycholanic acids (a- and ß-muricholic acids, VII, VIII) (41), and
OH
HO'
3a,6o:,7/?-trihydroxycholanic acid (ω-muricholic acid, IX) is formed
(41, 42) when rats are treated with 3a,6a-dihydroxycholanic acid
(hyodeoxycholic acid) well known as a constituent of pig bile (see
38). 3ß,6a- and 3«,6ß-Dihydroxycholanic acids have also been isolated from pig bile (30, 42-44), as well as the keto acid, 3a-hydroxy7-oxoallo(5α)cholanic (X) (45), which has a trans A/B junction and is
HO'
OH
HO"
OH
(IX)
probably formed from the corresponding cholanic (5ß) acid during
alkaline hydrolysis of the bile. Another widely distributed acid is
chenodeoxycholic (3a,7a-dihydroxy cholanic) (XI). Its epimer, 3a,7ßdihydroxycholanic, ursodeoxycholic acid (XII) has been found in coypu
HO"
OH
HO'
OH
(XI)
(XII)