Antimicrobial activity of saponins produced by two novel endophytic fungi from <i>Panax notoginseng</i>

<p>Endophytes in plants may be co-producer of the bioactive compounds of their hosts. We conducted a study to bioprospect for saponin-producing endophytic fungi from <i>Panax notoginseng</i> and evaluate the antimicrobial activity of saponins. Two novel fungal endophytes, <i>Fusarium</i> sp. PN8 and <i>Aspergillus</i> sp. PN17, were isolated from traditional Chinese medicinal herb <i>P</i>. <i>notoginseng</i>. After eight days of fermentation, the total saponins produced in the culture broth of PN8 and PN17 were 1.061 and 0.583 mg mL<sup>−1</sup>, respectively. The saponin extracts exhibited moderate to high (inhibition zone diameter 15.7–28.4 mm, MIC 1.6–12.5 mg mL<sup>−1</sup>) antimicrobial activity against pathogens tested. Further analysis showed that triterpenoid saponins produced by <i>Fusarium</i> PN8 were Rb<sub>1</sub>, Rd and 20(S)-Rg<sub>3</sub>, while <i>Aspergillus</i> PN17 had the ability to synthesise ginsenoside Re, Rd and 20(S)-Rg<sub>3</sub>. The isolated endophytes may be used as potential sources for microbial production of plant secondary metabolites and for antimicrobial agents.</p>