Lycopodiaceae herb from Vietnam as a promising medicinal source of natural hupezine and novel huperzine-producing endophytic fungi.

Objectives: (1) To evaluate the potential of producing huperzine (Hup) and anticholinesterase (AChE) activities of nine native Lycopodiaceae species collected in Vietnam; (2) Isolation, identification and characterization of a novel fungus producing both HupA and HupB isolated from Lycopodium casuarinoides Spring.

Results: All methanolic extracts of nine plants showed AChE inhibition from 8.55 to 71.81%. Of note, Huperzia serrata (Thunb.) Trevis, L. casuarinoides, Lycopodium clavatum L., Phlegmariurus squarrosus (G. Forst.), and P. phlegmaria (L.) T. Sen & U. Sen were shown to biosynthesize both HupA and HupB by high-performance liquid chromatography (HPLC). Plants H. serrata, L. casuarinoides and L. clavatum showed the most potent AchE IC inhibition. HupA and HupB concentrations from six plants were greater than those of previously reported Lycopodiaceae species. Sixty-four endophytic fungi were isolated from tissue of natural L. casuarinoides and then screened for HupA- and HupB-production by HPLC. Out of 64 fungal strains, only TTD2-2.7 extract could produce both HupA and HupB with the yields of 0.034 and 0.028 µg gdcw, respectively. Moreover, TTD2-2.7 extract also had inhibitory effects on AChE with the IC of 129.76 ± 4.13 µg ml, which was lower than the extract of host plant L. casuarinoides (94.03 ± 4.13 µg ml). The fungus was identified as Aspergillus sp. TTD2-2.7 by morphological characteristics and Internal Transcribed Spacer sequence analysis.

Conclusions: These are the first reports of (1) two species L. clavatum and L. casuarinoides producing both HupA and HupB, and (2) L. casuarinoides as novel sources of Hup-producing endophytic fungi as well as (3) fungus Aspergillus as a novel HupA- and HupB-producing endophyte isolated from L. casuarinoides.