Quercetin aglycone

Fig. 2.90. Electropherograms of sterile root exudate before (a) and after incubation with Mesorhizobium loti (b) and Rhizobium leguminosarum bv. trifolii (c). From their UV spectra, peaks 1-6 were identified as resorcinol, rhamnetin, catechin, quercetin glycoside, quercetin aglycone and hesperidin. Differences in the retention times of the same compounds in different samples could be due to the variations in buffer temperature or sample composition. Reprinted with permission from H. L. Steele et al. [213].

I. Erlund, T. Kosonen, G. Alfthan, J. Maenpaa, K. Perttunen, J. Kenraali, J. Parantanien and A. Aro, Pharmakokinetics of quercetin from quercetin aglycone and rutin in healthy volunteers. Ear. J. Clin. Pharmacol. 56 (2000) 545-552. 

Expressed as quercetin-3-rhamnoside (converted to quercetin aglycone). Source Reproduced from Kuhnau, J., World Rev. Nutr. Diet., 24, 117, 1976. With permission. 

Figure 2.18 HPLC profile of flavonols of a Brunello di Montalcino wine recorded at wavelength 360nm. (1) myricetin glucuronide, (2) myricetin glucoside, (3) quercetin glucuronide, (4) quercetin glucoside + quercetin rutinoside, (5) kaempferol glucuronide, (6) kaempferol glucoside, (7) quercetin aglycone...

Das demonstrated that oral administration of labeled 3-0-methylcatechin to three volunteers was followed by plasma peak levels within 2 hours after administration [69]. Hollman et al. studied the absorption of different glycosides of quercetin and the quercetin aglycone in nine healthy ileostomy subjects to avoid losses caused by colonic bacteria [30-31]. The absorption after oral administration decreased in the following order 52% for quercetin glucosides from fried onions > 24% for quercetin aglycone > 17% for quercetin nitinoside [31]. Consequently, humans absorb considerable amounts of quercetin, but the absorption depends on the glycosidic nature of the flavonoid [31]. 

Erlund I, Kosonen T, Alfthan G, Maenpaa J, Perttunen K, Kenraah J, Parantainen J, Aro A. Pharmacokinetics of quercetin from quercetin aglycone and rutin in healthy volunteers. Eur J Clin Pharmacol 2000 56 545-553. 

Morand C, Manach C, Crespy V, Remesy C. Respective bioavailability of quercetin aglycone and its glycosides in a rat model. Biofactors 2000 12 169-174. 

In a study comparing the absorption from dietary supplements of quercetin aglycone with rutin at various doses [16], ratin showed a clear maximal plasma concentration (of quercetin metabolites) at 6 h, with almost no quercetin in plasma at 4 h, indicative of absorption in the distal parts of the small intestine or in the colon. Late absorption was observed with all doses administered (16, 40, 100 mg rutin). In contrast, quercetin (8, 16, 50 mg aglycone) showed no clear maximal plasma concentration (tmax 1-9, 2.7, 4.9 h, respectively), but some absorption was observed from 30 min after ingestion, as is consistent with absorption along the length of the small and large intestine. 

The levels of the individual quercetin glucosides and quercetin aglycone were determined for the ethanol extracts from all the three onion powder samples. Changes in the composition of the quercetin conjugates due to drying... 

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