Pigments of the Moss Paraleucobryum longifolium: Isolation and Structure Elucidation of Prenyl-Substituted 8,8'-Linked 9,10-Phenanthrenequinone Dimers.

Dezső Csupor,Marianna Marschall,Norbert Kúsz,Katalin E Kövér,Tibor Kurtán,Péter Szűcs,Martin Vollár,Seyyed A Senobar Tahaei,István Zupkó,Attila Mándi,Judit Hohmann

doi:10.1021/acs.jnatprod.9b00655

Dezső Csupor, Marianna Marschall + Show 9 more

Open Access

https://doi.org/10.1021/acs.jnatprod.9b00655

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Abstract

In a search for new secondary metabolites from mosses, leucobryns A–E, axially chiral 9,10-phenanthrenequinone dimers, were isolated from Paraleucobryum longifolium (1–5), together with diosmetin triglycoside. Leucobryns B (2) and C (3) were proved to be homodimeric atropodiastereomers containing both axial and central chirality elements, while leucobryns D (4) and E (5) were found to be heterodimeric atropodiastereomers containing central chirality in only one of the two monomeric units. Axial chirality of the compounds was determined by ECD measurements and sTDA ECD calculations, while the central chirality elements were assigned by TDDFT-SOR calculations. Leucobryns represent the first 9,10-phenanthrenequinone dimers, the monomers of which are linked through their C-8 atoms. Leucobryns B–E contain an uncommon C10 monoterpenoid side chain, in which isoprenoid units are joined by 3,4 linkages. Leucobryns A and B exhibited weak antiproliferative activity against several human cancer cell lines.

Highlights

E (5) were found to be heterodimeric atropodiastereomers containing central chirality in only one of the two monomeric units
Axial chirality of the compounds was determined by ECD measurements and sTDA ECD calculations, while the central chirality elements were assigned by TDDFT-SOR calculations
The phytochemical and pharmacological potential of bryophytes is poorly explored because of the difficulties of their collection and botanical identification, numerous new compounds have been discovered from liverworts so far, including more than 40 new carbon skeletons of terpenoids and phenolic compounds.[1−5] Many moss species have been used as medicinal plants for infections and neurological disorders and for their nutritional value.[3−5] The biological effects ascribed to the compounds identified in liverworts are mainly related to cytotoxic, antimicrobial, antifungal, antiviral, insecticide, nematocide, enzyme inhibitory, antiallergic, muscle relaxant, and antioxidant activities.[3−6] Mono, sesqui, di, and triterpenoids, highly unsaturated fatty acids, flavonoids, bibenzyls, bis-bibenzyls, acetogenins, and phenanthrenes are the main chemical types of secondary metabolites of liverworts.[3−5]