II. CHEMISTRY 5G1 



response curve for oxybiotin seems to be different from that for biotin.'^' 

 The relati\-e actix'ity for oxybiotin is higher for a siiboptimal (6.0%) than 

 lor near maximal (2.9 %) response. For chicks it was claimed that oxybiotin 

 injected intramiiscularlj'- was approximately 17% as active as (+)-biotin 

 with the shape of the dose-response curve essentially similar for both 

 i-ompounds.'-'' In contrast, the statement was also made that oxybiotin, 

 w hen admhiistered as a supplement in the diet instead of being given paren- 

 lerally, fails to replace biotin completely for growth of the chick on a 

 biotin-deficient diet. Oxybiotin is reported to have about one-third the 

 activity of biotin in curing the specific cutaneous signs of biotin deficiency. 

 However, e\en withup to 100 7 per 1000 g. of diet, oxybiotin failed to support 

 optimal gr(n\tli in chicks. Thus it was assumed — without confirmation — 

 that oxybiotin, at least when given in the food, fulfilled only a part of the 

 function of biotin in the chick. ^"^ 



There are several methods available for the differential assay of biotin 

 and oxybiotin, respectively. Whereas Raney nickeP*- or oxidation with 

 permanganate^-^^ will destroy biotin, the same procedures leave oxybiotin 

 unaffected. Raney nickel converts biotin to desthiobiotin and permanganate 

 oxidizes biotin to corresponding sulfone. Neither of these compounds has 

 any appreciable activity for Lactohacillns arahinosus, as well as for several 

 other organisms. Thus, in such mixtures oxybiotin may be quantitatively 

 determined as a groAHh factor for L. arahinosus and similar organisms. 



Inasmuch as Streptococcus faecalis R. is imable to utilize oxybiotin effec- 

 tively, especially at low pH when it still responds to biotin, S. faecalis may 

 be used for the quantitative estimation of biotin with only negligible 

 interference from the oxygen analog. ^^^ 



A further indirect assay of biotin in the presence of oxybiotin depends 

 on the inhibitory effect of biotin sulfone or T-(3,4-ureylene-cyclohexyl)bu- 

 tyric acid in the response of Lactobacillus arahinosus for moderate amounts 

 of oxy biotin. ^^* Under these conditions, neither of the inhibitors appreciably 

 affects the utilization of biotin by the organism. 



With these assays, oxybiotin has been found not to occur naturally in 

 any of the organisms or animal tissues tested. On the other hand, it has 

 also been demonstrated that Saccharomyces cerevisiae, Rhizohium trifolii, 

 and Lactobacillus pentosus grown in the presence of oxybiotin utilized the 

 compound as such, and not after conversion into biotin. •-'*• ^'^^' '^^ Various 

 tissues taken from biotin-deficient chicks treated with oxybiotin have 

 yielded low values for biotin and appreciable amounts of the oxygen analog. 



131 K. Hofmann, J. Am. Chem. Soc. 71, 164 (1949). 



"2 K. Hofmaim, T. Winnick, and A. E. Axelrod, ./. Biol. Chem. 169, 191 (1947'. 



'" K. Hofmann and T. Winnick, J. Biol. Chem. 160, 449 (1945). 



l3^ A. E. A.xelrod, J. DeVVoody, and K. Hofmann, J. Biol. Chem. 163, 771 (1946). 



"5 A. E. Axelrod, B. C. Flin, and K. Hofmann, /. Biol. Chem. 169, 195 (1947). 



