5a-Cyprinol

Deoxy-5a-cyprinol 5a-Cholestane-3o,7a,12a,26-tetrol Some fishes some frogs and toads... 

Fig. 2. 5a-Cyprinol sulfate(IV), anhydro-5a-cyprinol(V), 5a-cyprinol(VI) and dehydroanhydro-5a-cyprinol(VII).

Deoxy-5a-cyprinol, 5a-cholestane-3a,7a,12a,26-tetrol, has been identified as a minor companion of 5a-cyprinol in the carp bile [31]. This tetrahydroxy-5a-bile alcohol was prepared from anhydro-5a-cyprinol (VII) by lithium aluminum hydride reduction [2], 27-Deoxy-5a-cyprinol also occurs in bile of fishes [32], toads [9,33], and frogs [9]. 

In a thorough analysis of solvolyzed material from bullfrog bile. Noma et al. isolated 4 new Cjj bile alcohols along with 5a-ranol, 5)3-ranol, and 5a-cyprinol [41]. Comparison with synthetic samples showed that these were 4 diastereoisomers at C-5 and C-24 of 26-deoxyranol, 27-norcholestane-3a,7a,12a,24-tetrol [41]. The... 

Okuda et al. isolated a higher bile acid from the bile of Iguana iguana [66]. The structure was shown to be 3a,7 ,12a-trihydroxy-5a-cholestan-26-oic acid by lithium aluminum hydride reduction to 27-deoxy-5 -cyprinol [66]. The 5a-C27 bile acid was also partially synthesized from 27-deoxy-5a-cyprinol [67]. 3a,7a,12a-Trihydroxy-5a-cho estan-26-oic acid also occurs in bile of some species of frogs [18,19] and the alligator [68],... 

The major bile salt of the carp, Cyprinm carpio, is 5a-cyprinol sulfate [21]. When [4- C]cholesterol was injected intraperitoneally into the carp, radioactive 5a-cyprinol was isolated from gallbladder bile [148]. It has been shown that the initial step in the major pathway for the formation of 5a-cyprinol (VI) from cholesterol (XV) is the 7a-hydroxylation of cholesterol to form cholest-5-ene-3j8,7a-diol (XVI) [149] (Fig. 4). It has also been shown that the double bond is isomerized to the A position before being reduced [150]. These in vivo studies suggest that until the intermediary formation of a A compound, presumably 7 ,12a-dihydroxycholest-4-en-3-one (XVII), the sequence of reactions in the biosynthesis of 5 -cyprinol (VI) in the carp is the same as that in the conversion of cholesterol (XV) to cholic acid (XIV) in mammals. 7a,12a-Dihydroxycholest-4-en-3-one (XVII) was found to be converted into 5a-cholestane-3a,7a,12a-triol (XVIII) by the microsomal fraction of carp hver fortified with NADPH [151]. The conversion of the triol (XVIII) to 5a-cyprinol (VI) via 27-deoxy-5a-cyprinol (XIX) was also established. The 26-hydroxylation of the triol (XVIII) was catalyzed by the microsomal fraction fortified with NADPH, and the 27-hydroxylation of 27-deoxy-5a-cyprinol (XIX) was catalyzed by the mitochondrial fraction fortified with NADPH [151]. 

The formation of 27-deoxy-5a-cyprinol and 5a-cyprinol in the carp has been shown by Hoshita (121) and Masui et al. (178) to involve 26(27)-hydroxylation of 5a-cholestane-3a,7a,12a-triol, catalyzed by the microsomal fraction fortified with NADPH, followed by 26(27)-hydroxylation of 27-deoxy-5a-cyprinol, catalyzed by the mitochondrial fraction fortified with NADPH. 

In the carp, chub, and related fishes, 5a-cyprinol is a principal bile alcohol (220). It also occurs in the lungfish and in the coelacanth, where it is accompanied by its 3/9-epimer, latimerol. The characterization of 5a-cyprinol was accomplished by Hoshita et al. (221) and by Anderson et al. (222)... 

The ancient bony fish, the coelacanth, has bile that contains little if any bile acid and has as its principal bile alcohol the compound shown above, which is latimerol. Latimerol was isolated and characterized by Anderson and Haslewood (227). It occurs along with its 3a-epimer, 5a-cyprinol. 

This alcohol has been isolated from the bile of the carp (228). It may be the alcohol isolated much earlier from the toad Bufo vulgaris japonica) by Makino (229) and named tetrahydroxybufostane (194). 27-Deoxy-5a-cyprinol was prepared from anhydrocyprinol by Hoshita (230). Its 5,3-epimer may be an expected intermediate in the formation of trihydroxycoprostanic acid, but the alcohol has not been widely found. Both the 5 - and 5 -epimers of 27-deoxycyprinol were formed in toads given C-cholesterol (194). 

A probable intermediate in the biosynthesis of allocholic acid, 3a,7a, 12a trihydroxy-5a-cholestan-26-oic acid, has been found in the bile of the giant salamander (39). Amimoto (43) obtained allocholic acid and a second radioactive acidic metabolite from bile of the giant salamander after administration of 27-deoxy-5a-cyprinol (3a,7a, 2a, 26-tetrahydroxy-5a-cholestane). The unknown acid was esterified, reduced with LiAlH4, and the product identified as 27-deoxy-5a-cyprinol. Okuda et at. (44) isolated a few crystals (m.p. 227 °C) from the bile of iguana and obtained the same product on reduction of the ester with LiAlH4. 

Hoshita et al. (39) reported the synthesis of this acid from anhydro-5a-cyprinol (26,27-epoxy-3o ,7a,12a-trihydroxy-5a-cholestane) (XV) as shown in Fig. 10. Kallner (66) and Ziller, Mitra, and Elliott (68,40) prepared the ester as described under A, 2 and A, 3 respectively. 

To ascertain whether cholesterol is a precursor of 5a-cyprinol, Hoshita (133) administered C-cholesterol intraperitoneally to carp, in which 5a-cyprinol is the principal biliary sterol (134). After 12 days bile was collected from the gallbladder, and radioactive 5a-cyprinol corresponding to 0.14% of the administered sterol was recovered from bile. To ascertain whether choles-tanol or 7a-hydroxycholesterol was a precursor of 5a-cyprinol in this species Hoshita (58) administered these tritiated sterols intraperitoneally to carp and studied the distribution of in biliary constituents. From cholestanol-5,6- H, 1.1% of the biliary remained in the neutral fraction, of which 5a-cyprinol and 27-deoxy-5a-cyprinol were the major and minor constituents ( 22 1). Allocholic acid was the only radioactive component identified in the acid fraction. Two weeks after similar injection of 7a-hydroxycholesterol-7/S- H into carp, 17.6% of the radioactivity was recovered in bile, 86.5% of which was present in the neutral fraction and 6.3 % in the acid fraction. 5a-Cyprinol and 27-deoxy-5a-cyprinol ( 9 1) retained most of the tritium in the former fraction, whereas allocholic and cholic acids each retained ( 1.5 1) in the acid fraction. Thus, carp liver enzymes convert 7a-hydroxy-cholesterol to 5a sterols and to the 5/9- and 5a-C24 acids. Normally carp bile contains more cholic than allocholic acid. 

Masui et al. (136) have shown that carp liver microsomes contain the necessary 5a-reductase and a 26-hydroxylase to convert 7a,12a-dihydroxy-cholest-4-en-3-one (XXXVI) to 27-deoxy-5a-cyprinol when fortified with NADPH, and that a mitochondrial enzyme system requiring NADPH converts the latter 5a-sterol to 5a-cyprinol. They suggested that the microsomal system hydroxylated one of the terminal methyl groups in a stereospecific form (25 -form), and the mitochondrial system hydroxylated the 25a-form. 

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