Acylglycerols (=Glycerides) from the Glandular Trichome Exudate on the Leaves of Paulownia tomentosa

Abstract

Chemical investigations of the glandular trichome exudates on the leaves of Paulownia tomentosa (Scrophulariaceae) led to the identification of the thirty acylglycerols (=glycerides) 1–30, including five known ones (2, 3, 6, 9, and 15) (Fig. 1). Spectroscopic analysis combined with GC/MS studies of the glycerides and the liberated fatty acids, in the form of trimethylsilyl ether derivatives and trimethylsilylated methyl esters, respectively, established that the constituents belonged to 1,3‐di‐O‐acetyl‐2‐O‐(fatty acyl)glycerols, 1‐O‐acetyl‐2‐O‐(fatty acyl)‐sn‐glycerols, and 2‐O‐(fatty acyl)glycerols, wherein the fatty acyl moiety was either an eicosanoyl or an octadecanoyl group bearing OH and/or AcO groups at the 3‐, 3,6‐, 3,7‐, 3,8‐, or 3,9‐positions. The 1‐O‐acetyl‐2‐O‐[(3R,6S)‐3‐(acetyloxy)‐6‐hydroxyeicosanoyl]‐sn‐glycerol (12; 20% of the total glycerides), 2‐O‐[(3R,8R)‐3,8‐bis(acetyloxy)eicosanoyl]glycerol (17; 14%), 2‐O‐[(3R,9R)‐3,9‐bis(acetyloxy)eicosanoyl]glycerol (18; 12%), and 2‐O‐[(3R)‐3‐(acetyloxy)eicosanoyl]glycerol (10; 12%) were relatively abundant constituents. The configurations of the stereogenic centers of the fatty acyl moieties were determined by 1H‐NMR analysis of the monoesters obtained from (R)‐ and (S)‐2‐(naphthalen‐2‐yl)‐2‐methoxyacetic acid ((R)‐ and (S)‐2NMAOH and the hydroxy‐substituted fatty acid methyl esters (Fig. 2). The configuration at C(2) of the glycerol moiety of the 1‐O‐acetyl‐2‐O‐(fatty acyl)glycerols was determined to be (2S) by chemical conversion of, e.g., G‐2 (=2/3 1 : 10) to (+)‐3‐O‐[tert‐butyl)diphenylsilyl]‐sn glycerol of known absolute configuration.

2-Acety-1-(3-glycosyloxyoctadecanoyl)glycerol and dammarane triterpenes in the exudates from glandular trichome-like secretory organs on the stipules and leaves of Cerasus yedoensis

“…The configuration at sn-2 of glycerol moiety was determined to be S by converting compound 1 to a known stereo-defined compound, 1,2-di-O-(S)-MTPA-3-O-TBDPS-sn-glycerol as reported in our previous paper (Asai et al, 2009). The configuration at C-3 of the fatty acyl moiety was determined to be R by applying Mosher's ester method (Ohtani et al, 1991) diazomethane treatment of the resulting 3-hydroxyfatty acid.…”

“…The configuration at C-3 of the fatty acyl moiety was determined to be R by applying Mosher's ester method (Ohtani et al, 1991) diazomethane treatment of the resulting 3-hydroxyfatty acid. The structure and the homogeneity of the methyl ester were further established by 1 H and 13 C NMR spectroscopic data, as well as GLC and EIMS (as trimethylsilyl ether) analyses in direct comparison with a reference material (Asai et al, 2009). Glucose and rhamnose were identified in the aqueous layer of the above acidic treatment by TLC and GLC (as their trimethylsilyl derivatives) analysis.…”

“…Solid secretions are referred to as food bodies (Bell and Bryan, 2010). We have been interested in phytochemical studies aimed at further understanding of the biological roles of the secondary metabolites in the secretions from such secretory organs of plants, and reported the characterization of oxygenated fatty acylglycerols from the glandular trichome exudate on the leaves of Paulownia tomentosa (Asai et al, 2009) and geranylated flavanones from the oily secretions on the surface of the plant's immature fruits (Asai et al, 2008). More recently we reported the identification of glycosylated fatty acids and dammarane triterpenes from the glandular trichome exudates on the leaves of Ibicella lutea and Proboscidea louisiana and cyclic fatty acyl glycosides in the glandular trichome exudates on the calyxes of Silene gallica .…”

n-Octyl .ALPHA.-L-Rhamnopyranosyl-(1.RAR.2)-.BETA.-D-glucopyranoside Derivatives from the Glandular Trichome Exudate of Geranium carolinianum

“…aq. NH 4 Cl and partitioned between n-BuOH and H 2 O. Concentration of the n-BuOH layer under reduced pressure gave an oily residue.…”

“…Our previous studies led to the characterization of a series of oxygenated fatty acyl glycerols, in the glandular trichome exudate on the leaves, and geranylated flavanones, in the oily secretion on the immature fruit surface, from Paulownia tomentosa (Scrophulariaceae). 3,4) The glandular trichome exudates of Ibicella lutea and Proboscidea louisiana (Martyniaceae) contained glycosylated fatty acids and dammarane triterpenes. 5) Recently we identified a series of cyclic fatty acyl glycosides from the glandular trichome exudate of Silene gallica (Caryophyllaceae) 6) and 2-acetyl-1-(3-glycosyloxy-fatty acyl)octadecanoyl-sn-glycerol and dammarane triterpenes from the glandular trichome-like secretory organs in the young stipules and leaves of Cerasus yedoensis (Rosaceae).…”