Abstract
Fischerella ambigua was isolated during a screening program from soil sample collected from paddy-fields in the north of Iran. It was shown that it excreted broad-spectrum antibacterial and antifungal substance in culture medium. Bioassay-guided fraction of the culture medium of the F. ambigua led to isolation of a novel antimicrobial substance, which was named parsiguine, that exhibited antifungal and antibacterial activities. The structure of parsiguine was determined by spectroscopic methods, including NMR, MS, IR, and UV.