Irregular sesquiterpenoids from Ligusticum grayi roots |
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Authors: | Laurence G Cool Karl E Vermillion Rosalind Y Wong |
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Institution: | a United States Department of Agriculture, Agricultural Research Service, 800 Buchanan St., Albany, CA 94710, USA b United States Department of Agriculture, Agricultural Research Service, 1815 N. University St., Peoria, IL 61604, USA |
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Abstract: | Root oil of Ligusticum grayi (Apiaceae) contains numerous irregular sesquiterpenoids. In addition to the known acyclic sesquilavandulol and a sesquilavandulyl aldehyde, two thapsanes, one epithapsane, and 14 sesquiterpenoids representing eight hitherto unknown carbon skeletons were found. These skeletons are: prethapsane, i.e. 1,1,2,3a,7,7-hexamethyloctahydro-1H-indene; isothapsane, i.e. 1,2,3a,6,7,7a-hexamethyloctahydro-1H-indene; ligustigrane, i.e. 1,1,2,7,7,7a-hexamethyloctahydro-1H-indene; isoligustigrane, i.e. 1,1,2,6,7,7a-hexamethyloctahydro-1H-indene; preisothapsane, i.e. 1,1,2,3a,6,7-hexamethyloctahydro-1H-indene; isoprethapsane, i.e. 1,1,2,4,7,7-hexamethyloctahydro-1H-indene; allothapsane, i.e. 1,1,2,3a,7,7a-hexamethyloctahydro-1H-indene; and oshalagrane, i.e. 1,1,2,4,6,6-hexamethylspiro4.4]nonane.The bicyclic sesquiterpenoids are presumably biosynthesized by head-to-head coupling of geranyl diphosphate and dimethylallyl diphosphate, followed by a cyclization sequence leading to a hydroindane skeleton with six one-carbon substituents. Subsequent rearrangements—primarily methyl migrations—account for the remarkable variety of structures represented in L. grayi root oil. |
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Keywords: | Ligusticum grayi Apiaceae Gray&rsquo s lovage Root Sesquiterpenoids Thapsane Epithapsane Prethapsane Isothapsane Preisothapsane Ligustigrane Isoligustigrane Allothapsane Isoprethapsane Oshalagrane |
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