From four Arnica species (A. angustifolia Vahl ssp. attenuata (Greene) Maguire, A. lonchophylla Greene ssp. lonchophylla Maguire (flowerheads), A. chamissonis Less. ssp. foliosa (Nutt.) Maguire, A. montana L. (roots and rhizomes)) a total of twelve lignans of the furofuran-, dibenzylbutyrolactone- and dibenzylbutyrolactol-type were isolated. No report on lignans as constituents of Arnica species exists so far. Besides the known pinoresinol, epipinoresinol, phillygenin, matairesinol, nortrachelogenin and nortracheloside, six dibenzylbutyrolactol derivatives with different stereochemistry and substitution at C-9 were isolated and their structures elucidated by NMR spectroscopic and mass spectral analysis.
Posters Planta Med. 57, Supplement Issue2 1991 R-O 2r HOH2C 0-Glucose 3 a R 2-O-acetyt-3,4-O-di-p-methoxycinnamoylrhsmflOse 3 b R = 4-O-acetyt-2,3-O-di-p-methcxycinnamOylrhatflflOSeture of both substances. They were characterized as 3a: 6-0-(2"-0-acetyl-3",4"-0-di-p-methoxycinnamoyl-a-L-rhamnopyranosyl)catalpol and 3b: 6-0-(4"-O-acetyl-2",3"-O-di-p-methoxycinnamoyl-a-L-rhamnopyranosyl)catalpol. Compound 4 was identified as acteoside, a phenyipropanoid previously isolated from S. scopolli (2), which is described here for first time in this plant.Compounds 3a and 3b were found to be very active in the topical inhibition of mouse ear edema induced by TPA (4) at a dose of 0.5 mg/ear. The effect was nearly the same as that of indomethacin, with a percentage inhibition of edema of73 .4%. 6 Chromenes (benzopyrans) and benzofurans are prominent natural products of many genera of the Asteraceae and have become useful taxonomic markers within this family (1, 2). Several of them have been shown to be biologically active (1). In previous papers (3, 4), we have reported on the occurrence of chromenes in the genus Am/ca. We now have isolated the chromenes 1-9 from the rhizomes and roots of Arn/ca chamissonis Less. ssp.foliosa (Nutt.) Maguire.Compounds 1, 3, 5, and 8 were identified on the basis of their mass and 1H-NMR spectral data. The constituents 2, 4, 6, and 7 occurred only in traces and were not obtained in pure form. Their identity was confirmed by direct comparison (TLC, GC, and GC-MS) with authentic samples. The structure of the minor constituent 9 followed from the GC-MS analysis. The mass spectrum IM 318] showed the same fragmentation pattern as 8, with only the ester group being changed. The characteristic fragments at m/z = 234 FM -C4H5=C=O] (62), 219 [M -(CH, + C4H5=C=O)]t (8), 203 [M -C4II9COOCH2Y (91), 201 FM -(CH3 + C4H9COOH)J (100), 175 FM -C4H9COOCH2CO] (1 8), 160 FM -(CH, + C4HCCOOCH2COW (49), 115 [C4H5COOCH2P (16), 85 [C4H9CO] (24), and 57 [85 -CO] (79) indicated clearly the presence of an isovaleryloxy or 2-methylbutyryloxy residue at C-12. H H H HO OH H OH HO OH H3CO H3C H3C'1( H C4H9yO H 0 H3C H3C'5" HO C4H5yON HO 0The chromenes 3, 4, 5, and 8 are found for the first time in the genus Am/ca. Compound 9 is a new natural occuring chromene. AcknowledgementsWe thank Dr. D. Wendisch, Zeniralbereich für Forachung und Entwicklung, Bayer AG Leverkusen, for recording the 1Fl-NMR spectra and Dr. U. Matthiesen, Institut für Physiologische Chemie der Heinrich-Heine-Universität Düsseldorf, for recording the mass spectra.
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