ELEVENTH MEDAL AWARD TABLE 3--ANTIMICROBIAL ACTIVITY OF 2,2'-THIOBIS-PHENOLS 311 No. Compound ----Minimum Inhibitory Level, ug./ml.----, S. aureus T. S. (in Presence E. menta- aureus of Soap) coli grophytes Substltuents 29 5O 5O 25 30 4-(•/•ioro 3.12 13_i • 25 3.12 3l 4-Bromo 3.12 12.5 25 3.12 32 4,6-Dichloro,(bithionol) 1.56 3• 12 50 0.78 33 6-Bromo-4-chloro 1.56 3.12 50 1.56 34 3,4,6-Trichloro 0.78 6.25 50 50 35 Tetrachloro 0.78 12.5 50 50 36 4-Chloro-6-isopropyl-3-methyl 3.12 12.5 50 50 37 4-Chloro-3,5-dimethyl 6.25 12.5 50 50 38 2_Hydroxy-2-methoxy-5,5'-dichloro. diphenylsulfide 6.25 12.5 50 12.5 TABLE 4--ANTIMICROBIAL ACTIVITY OF RELATED BIs-PHENOLS No. Compound -Minimum Inhibitory I.evel, ug./ml.- --. S. aureus T. S. (in Presence E. menta- aureus of Soap) coli grophytes 39 1,1'-Methylenebis(2-naphthol) 6.25 12.5 50 6.25 40 3,3'-Methylenebis (2,4,6= trichloro- ,p, henol) 6.25 12.5 50 3.12 41 3,3 -Methylenebls(4-bromo-2,6- ,d, ichlorophenol) 12.5 12.5 50 12.5 42 4,4 -Methylenebls(2,3,6-trichloro- phenol) 12.5 12.5 50 3.12 43 2,2'-Oxybis(tetrachlorophenol) 0.78 1.56 50 50 44 4,4'-Thiodiphenol 50 50 25 45 2,2'-Sulfinylbis(3,4,6-trichlorophenol) 12.5 1•i• 50 25 46 o,oLDiphenol 5(} 70 50 47 4,4',6,6'-Tetrabromo-o,o'-diphenol 1.56 •i i2 50 6.25 48 Salicil(2,2'-dihydroxybenzil) 50 50 50 49 5,5'-Dichlorosalicil 3.12 151• 50 1.56 TABLE 5--BIs-PHENOLS SHOWING INHIBITORY LEVELS OF 50 btC./ML. AGAINST THE THREE TEST ORGANISMS No. Compound 50 2,2'-Me th¾1enediphen(•l 51 2,2'-Meth3lenebis(4,6-dim ethylphenoB 52 2,2'-Methylenebis(6-bromo-4-methylphencl) 53 2,2'-Methylenebis(4-nltrophenol) 54 2,2'-Methylenebis(4,6-dichlororesorcinol) 55 2,2'-Methylenebis(3,5,6-trichloroanisole) 56 4,4'-Methylenebis(2,6-dibromophenol) 57 2,2'-Thiobis (4-chloroanisole) 58 2,2'-Sulfinylbis (4-chlorophenol) 59 2,2'-Sulfonylbis(4-chlorophenol) 60 2,2'-Dihydroxy-5,5'-dichlorobenzophenone 61 1,1'-Methylenebis(6-bromo-2-naphthol) 62 1,1'-Methvlenebis(3,6-dibromo-2-naphthol) 63 4,4'-(3,4-Dimethoxybenzylidene) dithymol 64 Bis(3,5-dichloro-2-hydroxybenzyl)amine

312 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS investigated the in vitro antimicrobial activity of a series of bis-phenols with --S--, --SO--, --SO2--, --S--S--, --Sa-- and --S4-- linkages mostly in the ortho positions to the hydroxyl groups. The organisms employed were Staphy/ococcus aureus, Salmonella paratyphi, Trichophyton gypseum and Toru/opsis minor. The authors stated, as we and others have also observed, that the 2,2'-thiobis-phenols are more bacteriostatic and fungi- static than the 4,4'-thiobis-phenols, and that the introduction of chlorine or bromine increased the antimicrobial activity considerably. None of the compounds tested inhibited S. paratyphi at a concentration lower than 12 •g./ml., whereas a number of compounds were active against T. gypseum and S. aureus at a level of 1 •g./ml. and less. The most potent of these compounds against these two organisms and against roeoru/opsis minor was 2,2'-thiobis(4,6-dichlorophenol). A series of 2,2'-methylenebis-phenols, 2,2'-ethylidene and 2,2'-benzylidenebis-phenols, and a number of other compounds were examined by Florestano and Bahler (12) for antibacterial activity in vitro against a variety of organisms. They found that the compounds showed more or less specificity against gram-positive bacteria, being distinctly more active against them than against the gram-negative species tested. Halogen substituents were essential for potency bromine rather than chlorine substitution resulted in greater activity against gram- positive organisms, while antibacterial action on the gram-negatives remained the same. Florestano and Bahler also stressed the significance of the position of the hydroxy groups in the rings. Wendel (13) examined five bis-phenols, Nos. 1, 6 and 8 of Table 1, No. 40 of Table 4 and 4,4'-methylenebis (3,5-dichlorophenol), for their anti- bacterial potency against S. aureus, S. a/bus and a Streptococcus. He confirmed previous findings, namely, that the bacterial activity is con- nected with the number of chlorine atoms in the rings, an increase being shown from two to four to six chlorines and that this enhancement is only evident if the hydroxyl groups are adjacent to the methylene bridge. From the date presented in Tables 1 to 5 we are able to draw certain general conclusions (some of them in conformity with the findings of others) with regard to the relationship of the antimicrobial properties of the bis- phenols and their chemical structure. However, before doing so, we would like to call attention to the two compounds most closely related to hexachlorophene, namely Nos. 2 and 3. No. 2, 2,2'-methylenebis- (4,5,6-trichlorophenol), demonstrated approximately the same activity as hexachlorophene being perhaps slightly more inhibitory against S. aureus in the presence of soap. No. 3, 2,2'-methylenebis (3,4,5-trichloro- phenol), was outstanding, not only on account of its activity against S. aureus, but also because it was the only Ns-phenol which showed a fair degree of bacteriostatis against gram-negative organisms. We have given its activity against E. co/i as 6.25 ug./ml. This value resulted from two