Isolation of glutathione-S-transferase inhibitors.

doxorubicin8). Inhibitors of this enzyme, ethacrynic acid and piriprost are already known and their potential therapeutic utility in combination with alkylating agents has been suggested by Tew and his colleagues9). Our group has been screening for novel inhibitors of glutathione S-transferase from microbial origin and we recently isolated tryptophandehydrobutyrine diketopiperazine10) (TDD) and rishirilide B11} (Fig. 1). Although the structures of these compounds are already known, it seems to be worth while to report their enzymological and biological properties because of their potential usefulness. Wereport here the inhibitory effect of these compounds on glutathione-S-transferase ac-