Diversity, Chemical Constituents, and Biological Activities of Endophytic Fungi Isolated From Ligusticum chuanxiong Hort

Abstract

The objective of this study was to evaluate the diversity of endophytic fungi of different parts of Ligusticum chuanxiong Hort (CX) and further characterize their biological activities and identify chemical compounds produced by these endophytic fungi. A total of 21 endophytic fungi were isolated and identified from CX. Penicillium oxalicum, Simplicillium sp., and Colletotrichum sp. were identified as promising strains by the color reaction. Comparing different organic extracts of the three strains, it was observed that the ethyl acetate extract of Penicillium oxalicum and Simplicillium sp. and the n-butanol extract of Colletotrichum sp. showed significant antioxidant and antibacterial activities. The ethyl acetate extracts of Penicillium oxalicum had outstanding antioxidant and antibacterial effects, and its radical scavenging rates for ABTS and DPPH were 98.43 ± 0.006% and 90.11 ± 0.032%, respectively. At the same time, their IC₅₀ values were only 0.18 ± 0.02 mg/mL and 0.04 ± 0.003 mg/mL. The ethyl acetate extract of Penicillium oxalicum showed MIC value of only 0.5 mg/mL against Escherichia coli and Staphylococcus aureus. By liquid chromatography-mass spectrometry (LC-MS), we found that Penicillium oxalicum could produce many high-value polyphenols, such as hesperidin (36.06 μmol/g), ferulic acid (1.17 μmol/g), and alternariol (12.64 μmol/g), which can be a potential resource for the pharmaceutical industry. In conclusion, these results increase the diversity of CX endophytic fungi and the antioxidant and antibacterial activities of their secondary metabolites.

Keywords: antimicrobial activity; antioxidant activity; chuanxiong; endophytic fungi; phenolic compounds.

FIGURE 1

Neighbor-joining tree of the ITS sequences of the endophytic fungi associated with CX. Numbers at nodes are bootstrap scores obtained from 1000 replications. Mucor racemosus was used as an out group.

FIGURE 2

Antioxidant activities of the P. oxalicum (A), Simplicillium sp. (B), and Colletotrichum sp. (C) extracts. a: ABTS scavenging activity. b: Hydroxyl radical scavenging activity. c: DPPH radical scavenging activity. d: Superoxide anion radical scavenging activity. a–d: Significant differences between different groups (p < 0.05).

FIGURE 3

Effects of ethyl acetate extracts from endophytic fungi on cell membrane integrity of E. coli, S. aureus, and P. aeruginosa by fluorescence microscope. (A) Untreated bacterial cells; (B) bacterial cells treated with P. oxalicum extracts at 2MIC; (C) bacterial cells treated with Simplicillium sp. extracts at 2MIC; (D) bacterial cells treated with Colletotrichum sp. extracts at 2MIC. The scale bar was 100 μm.