Isolation and Characterization of New Phenazine Metabolites with Antifungal Activity against Root-Rot Pathogens of <i>Panax notoginseng</i> from <i>Streptomyces</i>

Abstract

Three new phenazine metabolites, strepphenazine A-C (<b>1-3</b>), along with a known compound baraphenazine E <b>4</b> were isolated from the culture broth of a <i>Streptomyces</i> strain YIM PH20095. The structures were elucidated based on the spectral data. Compounds <b>1-4</b> showed different antifungal activity against <i>Fusarium oxysporum</i>, <i>Plectosphaerella cucumerina</i>, <i>Alternaria panax</i>, and <i>Phoma herbarum</i>, which caused root-rot disease of <i>Panax notoginseng</i> with minimal inhibitory concentrations (MICs) of 16-64 μg/mL; compared with compound <b>4</b>, compounds <b>1-3</b> showed better antifungal activity against some of these pathogenic fungi with MICs of 16-32 μg/mL, while compound <b>4</b> showed antifungal activity against <i>F. oxysporum</i>, <i>P. cucumerina</i>, and <i>A. panax</i> with the same MICs of 64 μg/mL. Thus, strain YIM PH20095 provides new sources for the development of biological control agents to prevent the infection of pathogenic fungi of <i>P. notoginseng</i>.