E/Z-Thesinine- O-4′-α-rhamnoside, pyrrolizidine conjugates produced by grasses (Poaceae)

• Published in: Phytochemistry (Oxford) 2008-06, Vol.69 (9), p.1927-1932
• Main Authors: Koulman, Albert, Seeliger, Claudine, Edwards, Patrick J.B., Fraser, Karl, Simpson, Wayne, Johnson, Linda, Cao, Mingshu, Rasmussen, Susanne, Lane, Geoffrey A.
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Chemical constitution; chemical structure; Festuca arundinacea; Fundamental and applied biological sciences. Psychology; Fungal plant pathogens; glycosides; Isoretronecanol; Lolium perenne; Magnetic Resonance Spectroscopy; Molecular Structure; Monosaccharides - chemistry; Monosaccharides - isolation & purification; Pathology, epidemiology, host-fungus relationships. Damages, economic importance; Phytopathology. Animal pests. Plant and forest protection; Plant Extracts - chemistry; Plant physiology and development; Poaceae; Poaceae - chemistry; Pyrrolizidine alkaloids; Pyrrolizidine Alkaloids - chemistry; Pyrrolizidine Alkaloids - isolation & purification; rhamnose; spectral analysis; trachelanthamidine
• ISSN: 0031-9422; 1873-3700
• DOI: 10.1016/j.phytochem.2008.03.017

E- and Z-thesinine- O-4′-α-rhamnoside, saturated pyrrolizidine conjugates from grasses (Poaceae) are reported. Based on direct infusion mass spectrometry we identified a novel alkaloid as a major component of perennial ryegrass ( Lolium perenne). Initial mass spectral data suggested it to be a pyrrolizidine conjugate. As this class of alkaloids has not been described before from grasses, we isolated it to elucidate its structure. The isolated alkaloid proved to be a mixture of two stereoisomers. The structures of the two compounds as determined by 1D and 2D NMR spectroscopy, were E-thesinine- O-4′-α-rhamnoside ( 1) and Z-thesinine- O-4′-α-rhamnoside ( 2). These identifications were supported by the characterisation by GC-MS and optical rotation of (+)-isoretronecanol as the necine base released on alkaline hydrolysis of these alkaloids. 1 and 2 together with the aglycone and a hexoside were also detected in tall fescue ( Festuca arundinacea). This is the first report of pyrrolizidine alkaloids produced by grasses (Poaceae).