Diversity, antibacterial and phytotoxic activities of culturable endophytic fungi from Pinellia pedatisecta and Pinellia ternata.

Background: Endophytic fungi of medicinal plants, as special microorganisms, are important sources of antibacterial compounds. However, the diversity and antibacterial activity of endophytic fungi from Pinellia Tenore have not been systematically studied.

Results: A total of 77 fungi were isolated from roots, stems, leaves, and tubers of Pinellia ternata and P. pedatisecta. All fungi were belonged to five classes and twenty-five different genera. Biological activities tests indicated that 21 extracts of endophytic fungi exhibited antibacterial activities against at least one of the tested bacteria, and 22 fermentation broth of endophytic fungi showed strong phytotoxic activity against Echinochloa crusgalli with the inhibition rate of 100%. Furthermore, four compounds, including alternariol monomethyl ether (1), alternariol (2), dehydroaltenusin (3) and altertoxin II (4), and three compounds, including terreic acid (5), terremutin (6), citrinin (7), were isolated from Alternaria angustiovoidea PT09 of P. ternata and Aspergillus floccosus PP39 of P. pedatisecta, respectively. Compound 5 exhibited strong antibacterial activities against Escherichia coli, Micrococcus tetragenus, Staphylococcus aureus, and Pseudomonas syringae pv. actinidiae with the inhibition zone diameter (IZD) of 36.0, 31.0, 33.7, 40.2 mm and minimum inhibitory concentration (MIC) values of 1.56, 3.13, 1.56, 1.56 μg/mL respectively, which were better than or equal to those of positive gentamicin sulfate. The metabolite 7 also exhibited strong antibacterial activity against P. syringae pv. actinidiae with the IZD of 26.0 mm and MIC value of 6.25 μg/mL. In addition, the compound 7 had potent phytotoxic activity against E. crusgalli with the inhibition rate of 73.4% at the concentration of 100 μg/mL.

Conclusions: Hence, this study showed that endophytic fungi of P. ternata and P. pedatisecta held promise for the development of new antibiotic and herbicide resources.