Tumor Inhibition by a Sulfhydryl-blocking Agent Related to an Active Principle of Garlic (Allium sativum)^*

Extracts of garlic (Allium sativum) contain a bactericidal agent which is formed by the action of an enzyme on a substrate present in garlic bulbs. The active principle formed by this enzymatic process is an alkylthiosulfinic alkyl ester (R-SO-S-R) which is an -SH inactivator and reacts rapidly with cysteine. Since cell processes dependent. upon the availability of reduced -SH groups have been implicated in both normal and malignant growth, several related alkylthiosulfinic esters were investigated for tumor-inhibitory effects. Enzymatically formed ethylthiosulfinic ethyl ester as well as various synthetically prepared alkylthiosulfinic alkyl esters were shown to have tumor-inhibitory effects in the test systems used. The implications of tumor inhibition by a compound which is an -SH inactivator are discussed.