Apigenin, hydrolysis

Fig. 2.55. Gradient reversed-phase HPLC analysis of flavonoids in white onions (a) and celery (b). ODS column of 150 X 3.9mm i.d particle size 5pm. Mobile phase 20min gradient of 15-35 per cent acetonitrile in water adjusted to pH 2.5 with TFA. Fowrate lml/min. Upper and lower traces represent samples before and after hydrolysis, respectively. Detection wavelength 365 nm. IS = internal standard Qc = quercetin Ap = apigenin Lt = luteolin. Reprinted with permission from A. Crozier et al. [159],...

An HPLC separation method with diode array detector and mass spectrometric (MS) detection equipped with atmospheric pressure ionization (API) was developed to determine flavone, flavonol, and flavanone in various vegetables, including green bean, broccoli, brussels sprouts, celery, kale, leek, onion, parsley, pepper (green, yellow, and red), and tomato (118). The flavonoids were analyzed as aglycones after acid hydrolysis. The extraction and acid hydrolysis conditions are based on previous work by Hertog et al. (119). Quercetin is the overall major flavonol, followed by kaempferol. The flavones, apigenin and luteolin, were found only in limited foods,... 

Hertog et al. (119) developed a fast HPLC method for the identification and quantification of five major flavonoid aglycones (quercetin, kaempferol, myricetin, luteolin, and apigenin) in freeze-dried vegetable and fruits. However, due to the inadequate resolution of quercetin and luteolin on RP-HPLC on Nova-Pak C]8, two different eluents of different solvent strength and viscosity were utilized. The conditions for hydrolysis and extraction were tested based on different conditions of hydrochloric acid concentration (1.2-2.0 M), reaction period (0.5-6 h), and meth-... 

Justesen and Knuthsen (2001) quantified, by HPLC and mass spectrometry, flavonoids in commonly eaten fresh herbs, including parsley. Five major flavonoid aglycones were detected and quantified by HPLC after acid hydrolysis apigenin,... 

Harborne compared the behavior of flavonoid glycosides and of several C-glycosyl compounds in a 1 1 solution of ethanol in 2 V hydrochloric acid at 100°, and found that the former are invariably hydrolyzed, whereas the latter are not. Thus, even apigenin 7-D-glucosiduronic acid, which is resistant to acid hydrolysis, is completely cleaved in 4 hours, whereas no C-glycosyl compound tested liberates sugar under these conditions. This procedure provides a convenient method for distinguishing between the two types of compound. 

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