Two new isochromans, panowamycins A and B, were purified by solvent extraction, silica gel and octadecylsilyl silica gel (ODS) column chromatography followed by preparative HPLC, from a culture broth of Streptomyces sp. K07-0010, together with the known compounds NFAT-133, conglobatin, piericidin C series and dinactin. Structures of panowamycins were elucidated as new analogs of NFAT-133 by spectroscopic studies including various NMR experiments. Panowamycins A and B showed moderate antitrypanosomal activity, with IC(50) values of 0.40 and 3.30 μg ml(-1), respectively.