Isariotins E and F, Spirocyclic and Bicyclic Hemiacetals from the Entomopathogenic Fungus <i>Isaria tenuipes</i> BCC 12625

Abstract

New spirocyclic and bicyclic hemiacetals, isariotins E (1) and F (2), together with TK-57-164A (3) were isolated from the entomopathogenic fungus Isaria tenuipes BCC 12625. The absolute configuration of 3 was addressed by application of the modified Mosher's method. Isariotin F (2) exhibited activity against the malaria parasite Plasmodium falciparum K1 with an IC(50) value of 5.1 microM and cytotoxic activities against cancer cell lines (KB, BC, and NCI-H187) and nonmalignant (Vero) cells with respective IC(50) values of 15.8, 2.4, 1.6, and 2.9 microM.