N - Substituted N'-Hydroxythioureas' GIL CLIFTON,'
SARAH
K.
BRTAST, 91,DCHARLES
G. S X I S X E R
Ucparlnitnl of Chi naislry, *\\'orth Ttxus Slate Unlvtrslty, Dtnton, 2'txus
76203
Received A u y u s t 7 , 1969 A series of S-substitut,ed .\"-hydroxyureas and ,\"-hydroxythioureas were prepared, aiid their iiihibilory properties have been examined in several microbial systems. The hydroxyt,hiourea analogs proved to be toxic t o growth of Lactobacillus arabinosus, Leuconostoc dextranicum, and Streptococcus faeculis at, about 2 pg,'ml; however, the growth inhibition was reversed by adding supplement,sof cysteine aiid other sulfhydryl compounds not of natural origin. The toxicity of these derivat,ives may be due to protein denaturation since in an isolated enzyme system (yeast alcohol dehydrogenase) t,he enzyme is progressively deactivated by increasing coiicent'rations of i\--substituted ,\:'-hydroxythioureas, and the toxicity is negated by the presence of a variety of SH compounds. 111 contrast, to the rather extensive st.udieswhich have been carried out on the biological propert'ies of hydroxyurea as well as ot,her urea derivatives, it, was surprising to observe that' little data had been reported concerning the physiological propert,ies of hydroxythiourea derivatives. Thiourea per se has been utilized by plant physiologists in a variety of biological systems to affect, germination and g r o ~ t , hand , ~ cert'ain thiourea derivatives have been widely examined as chemot,herapeut,ic agent's. Hydroxyurea appare~it~ly inhibit's t,he synthesis of deoxyribonucleic acid in Escherichia C O Z ~ , ~ J ascites tumor cells,s and rat liver.g It has also proven t.o be eff ect'ive against a variet8yof leukemias and thus has been chosen for clinical evaluation.1o I n addition, N methyl-N'-hydroxyurea has been shown to be an impressive antmimicrobialagent which is active against pat,hogenic organisms." The present study is concerned with the inhibitory properties of some N-substituted N'-hydroxythioureas in various microbial systems, as well as a selected enzyme system, and with the reversal of these toxicities by sulfhydryl compounds. For comparative purposes, the corresponding N-subst'ituted N'-hydroxyureas were also prepared and examined in concurrent assays.
Experimental Section Microbiological Assay Procedures.-For the lactic acid bacteria a previously described amino acid medium'z was employed with the addition of calcium pantothenate at 0.2 pg/ml, and with additional modifications as noted: for Streptococcus j a c d i s 8043, 20 pglml of L-glutamine was added asept,ically without heating to each assay tube; for Leuconostoc dcrctranicunz 8086, 0.02 pglml of pantethine was added, and the phosphate concentration was increased fourfold. All of the la& bacteria assays were incu(1) Supported in part by the Kational Cancer Institute. Xational Institutes of Health (CA 8102), and b y the North Texas State University Faculty Research Fund. (2) N.D.E.A. Predoctoral Fellow, Title IV. (3) A. Poljakoff-Mayber and A . M. hlayer, I n d i a n J . Plant Phuaiol., 3, 128 (1960). (4) D. C. Ychroeder, C h e m . R e s . , 66, 181 (1955). ( 5 ) H. H. Fox, "Medicinal Chemistry." Alfred Burger, Ed., Interscience, S e w Tork, N. Y.1960, pp 970-996. (6) H . 9. Rosenkrana, A . J. Garro, J. .4. Levy, and H. S. Carr, B i o c h i m . Biophya. S e t a , 114, 501 (1966). (7) H . 8 . Rosenkranz and H. S. Carr, J . B a c t e r i d . , 93, l i s (1966). ( 8 ) J. W.Tarbro, B. J. Kennedy, and C . P. Barnum, Proc. 'Vat. Acud. Sei. U . S., 63, 1033 (1965). (9) J. W. Yarbro, W. G. Niehaus, and C. P. Barnum, Biochem. B i o p h y s . Ren. Commun., 19, 582 (1965). (10) 13. Stearns, I
