Ipangulines and minalobines, chemotaxonomic markers of the infrageneric Ipomoea taxon subgenus Quamoclit, section Mina
A comprehensive GC–MS analysis of 8 spp. revealed altogether 52 ipangulines (unique platynecine esters) and 21 minalobines (unique trachelanthamidine esters), respectively. Two minalobines have been isolated and structurally elucidated. A comprehensive GC–MS analysis of 8 Ipomoea species belonging t...
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Veröffentlicht in: | Phytochemistry (Oxford) 2005, Vol.66 (2), p.223-231 |
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Zusammenfassung: | A comprehensive GC–MS analysis of 8 spp. revealed altogether 52 ipangulines (unique platynecine esters) and 21 minalobines (unique trachelanthamidine esters), respectively. Two minalobines have been isolated and structurally elucidated.
A comprehensive GC–MS analysis of 8
Ipomoea species belonging to the subgenus Quamoclit, section Mina revealed that the members of this taxon form combinations of two necine bases with rare necic acids resulting in unique pyrrolizidine alkaloids. The occurrence and diversity of these metabolites show remarkable variations: Some species, especially
Ipomoea hederifolia and
Ipomoea lobata, are able to synthesize a large number of alkaloids whereas others, especially
Ipomoea coccinea and
Ipomoea quamoclit, are poor synthesizers with only a few compounds. However, these metabolites are apparently chemotaxonomic markers of this infrageneric taxon in general. They represent either esters of (−)-platynecine (altogether 48 ipangulines and 4 further esters including results of a previous study) or esters of (−)-trachelanthamidine, an additional novel structural type called minalobines (altogether 21 alkaloids). Both types are characterized by section-specific rare necic acids, e.g., ipangulinic/isoipangulinic acid, phenylacetic acid. The alkaloids of
Ipomoea cholulensis,
I. coccinea,
I. hederifolia,
Ipomoea neei, and
Ipomoea quamoclit were mono and diesters of platynecine. Minalobines turned out to be metabolites of
I. lobata (Cerv.) Thell. (syn.:
Mina lobata Cerv.) lacking ipangulines. The major alkaloid of this species, minalobine R, has been isolated and identified as 9-
O-(
threo-2-hydroxy-2-methyl-3-phenylacetoxy-butyryl)-(−)-trachelanthamidine on the basis of spectral data. Apparently only two of the species included in this study,
Ipomoea cristulata and
Ipomoea sloteri, are able to synthesize both, ipangulines as well as minalobines. Minalobine O could be isolated as a major alkaloid of
I. cristulata, its structure has been established as 9-
O-(
erythro-2-hydroxy-2-methyl-3-tigloyloxy-butyryl)-(−)-trachelanthamidine on the basis of spectral data. |
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ISSN: | 0031-9422 1873-3700 |
DOI: | 10.1016/j.phytochem.2004.11.019 |