LC-MS analysis of plant phenols

The study of natural products in plant extracts is an interesting challenge to LC-MS. Generally, the relevant compounds must be detected as minor components in complex mixtures. A combination of LC separation, especially to resolve isomeric stractures, and MS detection is needed. Furthermore, structural information is needed for the identification and dereplication of the unknown plant constituents. Because of the complexity of the sample pretreatment procedures involved in the isolation, MS in most cases is the only applicable spectrometric technique too much of a purified component would be needed for IR and NMR analysis. On-line analysis in relatively erode samples is obligatory for the detection of minor constitnents. When electrospray ionization (ESI) or atmospheric-pressnre chemical ionization (APCl) are applied for analyte ionization, structural information mnst be obtained by application of colhsion-indneed dissociation (CID), either via in-sonree CID or preferably via MS-MS or MS . LC-MS and LC-MS-MS have proved to be extremely snccessful in this area. 

Whereas LC-MS has been applied in the detection and characterization of other plant natnral prodnets, it was decided to foens on plant phenols, especially flavonoids. A general classification of plant phenols is given in Table 15.1. The application of MS to plant phenol characterization was reviewed [1]. 

Phenolic acid QC, Gallic acid, salicylic acid 

Hydroxycinnamic acids QC3 Ferulic acid, chlorogenic acid 

LC-MS plays a significant role in the analysis, dereplication, identification, and structural characterization of flavonoids. The MS analysis of flavonoid aglycones and flavonoid glycosides was reviewed by Cuyckens and Claeys [3], 

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