<jats:title>ABSTRACT</jats:title><jats:p>Bioassay-guided fractionation of the extract from the fermentation broth of<jats:italic>Streptomyces</jats:italic><jats:italic>spectabilis</jats:italic>BCC 4785 led to the isolation of three principle antimalarial agents, metacycloprodigiosin, bafilomycin A<jats:sub>1</jats:sub>, and spectinabilin. Metacycloprodigiosin exhibited potent in vitro activity against<jats:italic>Plasmodium</jats:italic><jats:italic>falciparum</jats:italic>K1, with a 50% inhibitory concentration of 0.0050 ± 0.0010 μg/ml, while its cytotoxicity was much weaker.