title: Ipangulines and minalobines, chemotaxonomic markers of the infrageneric Ipomoea taxon subgenus Quamoclit, section Mina.
abstract: 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.
authors.affiliation: Institut für Pharmazie (Pharmazeutische Biologie), Freie Universität Berlin, Königin-Luise-Strasse 2+4, D-l4195 Berlin, Germany.
authors.forename: Kristina
authors.initials: K
authors.lastname: Jenett-Siems
authors.forename: Sonja C
authors.initials: SC
authors.lastname: Ott
authors.forename: Thomas
authors.initials: T
authors.lastname: Schimming
authors.forename: Karsten
authors.initials: K
authors.lastname: Siems
authors.forename: Frank
authors.initials: F
authors.lastname: Müller
authors.forename: Monika
authors.initials: M
authors.lastname: Hilker
authors.forename: Ludger
authors.initials: L
authors.lastname: Witte
authors.forename: Thomas
authors.initials: T
authors.lastname: Hartmann
authors.forename: Daniel F
authors.initials: DF
authors.lastname: Austin
authors.forename: Eckart
authors.initials: E
authors.lastname: Eich
mesh_terms: D008401:Gas Chromatography-Mass Spectrometry; D027741:Ipomoea / Q000737:chemistry* / Q000145:classification / Q000235:genetics*; D015394:Molecular Structure; D011763:Pyrrolizidine Alkaloids / Q000032:analysis* / Q000737:chemistry / Q000302:isolation & purification
chemical_list: D011763:Pyrrolizidine Alkaloids