Diacyl CGAs

Monoacyl CGAs are more polar than the diacyl CGA, so they eluted first and appeared early in the chromatogram [6-8,10,11,13,15-20]. Generally, water, acetic acid, methanol, and acetonitrile have been used as solvents for HPLC with reverse phase stationary phases, such as C18, C8, phenyl hexyl, and diphenyl. 

The diacyl and triacyl CGAs behave similarly, giving the equivalent parent ion [diacyl CGA H] and [triacyl CGA H], respectively [7,10-13,20]. AU diacyl CGAs either produce [diacyl CGA—cinnamoyl—H] (Figs. 11-13) or [diacyl CGA—cinnamoyl H2O H] (Figs. 14 and 15). 

Fragmentation of the MS base peak for 3,5-diCQA yields a comparatively intense [caffeoyl—H] ion (Ai = 50% of base peak) (Fig. 13). This is consistent with [3-CQA—H] being the MS base peak rather than [5-CQA-H] where only a weak [caffeoyl—H] is detected. Based on these arguments, the acylated residue at position 4 is the most difficult to remove, whereas that at position 5 is the easiest. These facts are also true for CFQA and other hetero-diacyl CGAs (Figs. 16-20 and Table 4) [10,11,20]. 

TABLE 4 MS, MS, and MS Data of Diacyl CGAs in Negative Ion Mode... 

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