posted on 2021-09-23, 14:37authored byFriederike Lünne, Jens Köhler, Christina Stroh, Lena Müller, Constantin G. Daniliuc, Christian Mück-Lichtenfeld, Ernst-Ulrich Würthwein, Melanie Esselen, Hans-Ulrich Humpf, Svetlana A. Kalinina
Claviceps purpurea is an ergot fungus known for
its neurotropic alkaloids, which have been identified as the main
cause of ergotism, a livestock and human disease triggered by ergot
consumption. Tetrahydroxanthone dimers, the so-called ergopigments,
presumably also contribute to this toxic effect. Overexpression of
the cluster-specific transcription factor responsible for the formation
of these pigments in C. purpurea led to the isolation
of three new metabolites (8–10).
The new pigments were characterized utilizing HRMS, NMR techniques,
and CD spectroscopy and shown to be xanthone dimers. Secalonic acid
A and its 2,4′- and 4,4′-linked isomers were also isolated,
and their absolute configuration was investigated. The contribution
of secalonic acid A, its isomers, and new metabolites to the toxicity
of C. purpurea was investigated in HepG2 and CCF-STTG1
cells. Along with cytotoxic properties, secalonic acid A was found
to inhibit topoisomerase I and II activity.