Infraspecific Variation of Huperzine A and B in Icelandic Huperzia selago Complex.

The alkaloids huperzine A and huperzine B were originally isolated from the Chinese club moss . They are known inhibitors of acetylcholinesterase, and especially huperzine A shows pharmaceutical potential for the treatment of Alzheimer's disease. Its supply heavily relies on natural plant sources belonging to the genus , which shows considerable interspecific huperzine A variations. Furthermore, taxonomic controversy remains in this genus, particularly in the group. With focus on Icelandic taxa, we aimed to explore the relatedness of species using multi-locus phylogenetic analysis, and to investigate correlations between huperzine A contents, morphotypes, and genotypes. Phylogenetic analysis was performed with five chloroplastic loci (the intergenic spacer between the photosystem II protein D1 gene and the tRNA-His gene, maturase K, ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit, tRNA-Leu, and the intergenic spacer region between tRNA-Leu and tRNA-Phe). Huperzine A and huperzine B contents were determined using an HPLC-UV method. The phylogenetic analysis suggests that previously proposed and should not be considered species, but rather subspecies of . Three genotypes of Icelandic were identified and presented in a haplotype networking diagram. A significantly (p < 0.05) higher amount of huperzine A was found in genotype 3 (264 - 679 µg/g) than genotype 1 (20 - 180 µg/g), where the former shows a typical green and reflexed "selago" morphotype. The huperzine A content in genotype 3 is comparable to Chinese and a good alternative huperzine A source. Genotype 2 contains multiple morphotypes with a broad huperzine A content (113 - 599 µg/g). The content of huperzine B in Icelandic taxa (6 - 13 µg/g) is much lower than that in Chinese (79 - 207 µg/g).