Cyclohexadepsipeptides from the insect pathogenic fungus Hirsutella nivea BCC 2594

Two new cyclohexadepsipeptides, hirsutatins A (1) and B (2), were isolated from a culture filtrate of the insect pathogenic fungus Hirsutella nivea BCC 2594. Structures of these compounds were elucidated primarily by NMR and mass spectroscopic analyses. The alpha-carbon stereochemistry of 1 was established by HPLC analysis of its acid hydrolysate using a chiral column. Hirsutatin B (2) exhibited activity against the malarial parasite Plasmodium falciparum K1 with an IC50 value of 5.8 microg/mL, while hirsutatin A (1) was inactive at a concentration of 20 microg/mL.