3. Results and discussion
The profile of phenolic compounds in fresh lettuce extract was
determined by HPLC analysis. Relative changes in the concentration
of individual phenolic compounds in lettuce with time as
influenced by the addition of 0.5% AA, 0.05% cysteine, 0.5% CA
and 0.5% OA at 25 C were compared to that of the control. Protocatechuic
acid, chlorogenic acid, caffeic acid, p-coumaric acid, ferulic
acid and phloridzin were identified by matching the retention
time of the compounds determined in the lettuce extract to those
of pure standards (Fig. 1). The chemical structures of the peaks
identified in the lettuce extract were further confirmed by comparing
their UV spectra to those of pure standards.