The Chemical Ecology of Hydrastis Canadensis L. (Ranunculaceae): Effects of Root Isoquinoline Alkaloids on the Hydrastis Endophyte, Fusarium oxysporum

Abstract

Goldenseal (Hydrastis canadensis L., Ranunculaceae) is a popular medicinal plant and has been listed in Appendix II of the Convention on International Trade in Endangered Species (CITES). The herbaceous perennial is distributed in North America under deciduous forest canopies throughout much of the south and eastern seaboard north into Canada. The rhizome, rootlets and root hairs produce medicinally active alkaloids. Although berberine, one of the Hydrastis alkaloids, has shown anti-fungal activity, the influence of Hydrastis alkaloids on the plant rhizosphere fungal ecology has not been investigated. While a Fusarium spp. was previously isolated from H. canadensis, this is the first report of a F. oxysporum endophyte isolated from Hydrastis root tissue. Additionally, F. solani was isolated from non-rhizosphere soil surrounding Hydrastis root tissue. A bioassay was developed to study the effect of goldenseal isoquinoline alkaloids on three Fusarium isolates, including the two species isolated from Hydrastis. And, in order to accurately detect the alkaloids, a HPLC-MS method was developed. The whole root extract treatment stimulated macroconidia germination and chlamydospore formation, while inducing mycotoxin production in the Hydrastis endophyte. Chlamydospore formation, macroconidial germination and mycotoxin production of PSU isolate, F. commune, was reduced by the whole root extract. The second Hydrastis isolate, F. solani, responded to the whole root extract by increasing germination rates, but with no other effects. The findings suggest that the Hydrastis root extract appears to provide selective advantage for the endophytic isolate and influences the fungal ecology associated with its root system.