Diversity of Endophytic Fungi in Huperzia serrata and Their Acetylcholinesterase Inhibitory Activity

Abstract

Huperzia serrata is a Huperzine A (HupA)-producing herb. HupA is a potent, reversible, highly specific, centrally active and selective acetylcholinesterase inhibitor, and is commonly used to improve Alzheimer’s disease.At present, H. serrata resources have been overexploited and their artificial cultivation has lagged behind the need, so the market demand cannot be met. In this study, the diversity of the endophytic fungi in H. serrata was studied by high-throughput sequencing and traditional culture methods. Furthermore, the ability of the isolated endophytic fungi to produce acetylcholinesterase-inhibiting activity was evaluated. The results related to the diversity of fungi between high-throughput sequencing and traditional culture methods were compared. With high-throughput sequencing, five phyla, 22 classes, 55 orders, 120 families, and 178 genera of fungi were detected in Hubei Province, and five phyla, 22 classes, 54 orders, 124 families, and 196 genera were detected in Fujian Province. After cultivation with traditional culture methods, two phyla, three classes, five orders, six families, and six genera were detected in Hubei, and one phylum, three classes, five orders, five families, and six genera in Fujian. The endophytic fungi of H. serrata are highly diverse, and the results of high-throughput sequencing comprehensively reflect their community compositions. When the acetylcholinesterase-inhibiting activity of the isolated and cultured endophytic fungi was determined, five and three endophytic fungi from Hubei and Fujian Provinces, respectively, had good inhibitory activity (inhibition rate > 50%). Most of them were separated from leaf tissue. The strain HBR-1 and strain FJL-5 had the strongest inhibitory effects on AChE, with inhibition rates of 72.34% and 60.54%, respectively. Although only a proportion of the endophytic fungi was isolated with traditional culture methods, metabolites with broad potential applications can be isolated from these fungal cultures. The combination of high-throughput sequencing and traditional culture methods can be used to isolate and purify endophytic fungi in a targeted manner, gain many endophytic fungi, and enrich the endophytic fungi resource library.