New compounds from Metaxya rostrata

Metaxya rostrata C. Presl (Metaxyaceae) is a tree fern and its rhizome is used as traditional herbal remedy against intestinal diseases in Costa Rica. Until now, very unusual methylene-cylcopropane glucosides, betulinic acid, polyphenols, glycosides of phenolic acids and common sterols are known from the rhizome of this plant [1]. In recent investigations, the very potent cytotoxic substance 2-deprenyl-rheediaxanthone B, which causes active cell death by a mechanism similar to mitotic catastrophe, was isolated [2]. In continuation of these studies, the aqueous and the ethylacetate extract of the rootlets were further analyzed and fractionated by partition and different chromatographic methods such as vacuum liquid chromatography on silica, gel permeation chromatography on Sephadex^Ò LH20 and solid phase extraction on RP-18 as stationary phases. Besides the known compounds squalen and fern-9(11)-en [3], four new natural compounds were isolated. Their structures were elucidated on the basis of detailed spectroscopic data analysis (NMR, MS) as (4'E)-1-O-(β-glucopyranosyl)-N-(2'-hydroxytetracosanoyl)-4,8-sphingadienine (d18:2/h24:0-GlcCer) (1), to our knowledge the first glucoceramide identified in a fern, (2E)-2-(hydroxy-hexyliden)cyclopropyl-1®3-diglucoside (2), (6E)-6[2-(ß-glucopyranosyloxy)cyclopropyliden]-hexanoic acid methylester (3) and 2-deprenyl-7-hydroxy-rheediaxanthone B (4).

Fig. 1

References:

[1] Kainz KP, Virtbauer J, Kählig H, Arion V, Donath O, Reznicek G, Huber W, Marian B, Krenn L. Helv. Chim. Acta 95: 1531 – 7 (2012)

[2] Kainz K, Krenn L, Kählig H, Zehl M, Berger W, Bursch W, Marian B. PlosOne, submitted

[3] Merkinger B. Diploma Thesis, University of Vienna, 2011