Simple Esters — Occurrence and Structural Analysis

Gallic acid is almost invariably found in plant tissues in ester form (109). Various simple esters of gallic acid have been described from plant sources (Table 1 and Table 5) and these metabolites are in many ways analogous to the hydroxycinnamoyl esters occurring in plants (31). These esters are thus formed by association with sugars, polyols, glycosides and other phenols. In contrast to the hydroxycinnamic acids however (100), fully authenticated examples of the occurrence of N-acyl derivatives (with amines, amino-acids and alkaloids) of gallic acid have not yet been described in the literature. 

Camellia sinensis Camellia sinensis Bergenia crassifolia Bergenia cordifolia Camellia sinensis Camellia sinensis Bergenia crassifolia Bergenia cordifolia Arctostaphylos uva-ursi 

Aconiun lindleyi Tellima grandiflora Euphorbia sp. Euphorbia sp. Tolmiea menziesii Acacia farnesiana 

5-o-Galloylquinic acid (theogalHn) Camellia sinensis Theaceae 69) 

A further means for ready identification of a galloyl ester is by mass spectrometry of the methylated (diazomethane) ester. The mass spectral fragmentation pattern usually displays the ion (13) as base peak, m/e 195 22, 63). 

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