712 THE BIOCHEMISTRY OF B VITAMINS 



fungi, including Nematospora gossypii, 5d> 60 Lophodermium pinastri 60 and 

 Eremothecium ashbyii.® 1 The compound has been shown to be an absolute 

 essential for only a few organisms, such as Rhizopus suinus 62 and 

 "inositolless" mutant strains of Neurospora crassa. 63 



Woolley in 1940 isolated the "mouse anti-alopecia factor" from liver 

 concentrate and identified it as inositol. 64, 65 He showed that a loss of hair 

 and a severe dermatitis developed in mice on a purified diet and that the 

 administration of inositol cured these symptoms. 



Vitamin-like effects of inositol have also been reported for rats, 66, 67, 68, 69 

 guinea pigs, 70 hamsters, 71, 72 chicks, 73, 74 and pigs. 75 



Specificity 



Inositol, in contrast to other B vitamins, has a number of naturally 

 occurring, closely related analogues. Several of its geometrical isomers and 

 their derivatives are present in many natural products. 



Nine geometrical isomers of inositol are theoretically possible if the 

 six carbon atoms of the cyclohexane ring are considered to be coplanar. 

 These nine forms 76 are schematically represented below (Figure 9). 

 Four of these isomers (?^eso-inositol, ( + )- and ( — ) -inositol, and 

 scyllitol) are known to occur naturally either in the free state or in the 

 form of their esters or ethers. Their configurations as they are repre- 

 sented in Figure 9 have been established by the work of Posternak. 79, 80, 81 

 Three others isomers (epwnositol, aUo-inositol and muco-inositol) have 

 been synthesized and characterized. 79, 82, 83 



The possibility of additional isomers of compounds structurally related 

 to inositol has been indicated by x-ray studies on the /^-isomer of 1,2,3,4,- 

 5,6-hexachlorocyclohexane and the corresponding bromo derivative. 

 These studies 77, 78 indicate that the six carbon atoms do not lie in one 

 plane but in two parallel planes. This so-called "puckered ring" (chair 

 form) would make 16 isomers theoretically possible including six optically 

 active forms. While such structures may be stable in crystalline form, 

 it is possible that in solution such isomers resulting solely because of the 

 "puckered ring" or chair form of the cyclohexane ring may become inter- 

 convertible. 



The biological activity of the four naturally occurring isomers and 

 some of their most common derivatives 76 are listed in Table 49. Of all 

 these substances only meso-inositol was found to have vitamin activity 

 for both yeast and mice. 84 Indeed, in most instances only meso-inositol 

 or compounds which can readily form meso-inositol appear to be effective. 

 Esters of meso-inositol are active for mice but inactive for yeast. For 

 yeast only mytilitol (the methyl homologue of scyllitol) and hydroxy- 

 mytilitol have some activity in addition to meso-inositol itself. 



