Discovery, chemistry, and chemical biology of microbial products

Our long-standing and continual screening of microorganisms, especially for antiparasitic agents, has produced a wide variety of compounds of global importance, such as the avermectins. Recent discoveries include nafuredin, atpenins, argifin, and argadin. Nafuredin is a helminth-specific inhibitor of electron-tran sport enzyme, complex I, which exhibits anthelmintic activity against Haemonchus contortus in sheep. The atpenins are the most potent complex II inhibitors ever reported. Co-crystallization study of atpenin A5 and E. coli complex II indicated the binding mechanism of ubiquinone to complex II. Argifin and argadin are the first cyclic peptides to inhibit chitinase at low concentration. Though structurally similar, their chitinase inhibition mechanisms are quite different.