The antifungal potential of 12 isolates of Streptomyces derived from the bottom sediments of Trondheim Fjord, the Norwegian Sea, was investigated. It was found that the metabolites produced by the Streptomyces sampsonii INA01478 strain had pronounced antifungal activity against the opportunistic fungi Candida albicans and Fusarium oxysporum. To analyze the biologically active metabolites formed, a method of preparative separation using HPLC and a method for isolating individual compounds from the eluent were selected. The chromatograms of the tested samples obtained using the HPLC method showed two peaks with close retention times. Repeated preparative HPLC resulted in the isolation of two pure compounds that were identified using NMR and an MS data analysis. The major component of the subfraction was determined to be daidzein ([7-hydroxy-3-(4-hydroxyphenyl)-4H-1-benzopyran-4-one]), an isoflavonoid that has previously been described. The minor component had a similar but simultaneously different structure, the establishment of which is being studied. Daidzein exhibited a direct antifungal effect at 25 – 30 mm on Saccharomyces cerevisiae INA 01042 and the opportunistic filamentous fungi Aspergillus niger ATCC 16404 and Fusarium oxysporum VKPM F-148 and was totally inactive against the bacterial test organisms.

Daidzein is a naturally occurring phytoestrogen belonging to the group of non-steroidal estrogens. It is structurally similar to mammalian estrogen, so it can replace and/or inhibit it and thus has protective effects against diseases associated with estrogen control. _{[Goleij P et al., 2004].} In addition, daidzein inhibits oxidative damage and regulates immune reactions and apoptosis. Daidzein has a wide range of pharmacodynamic properties and represents a promising compound for drug development.