Absorption, Bioavailability, and Metabolism of Flavonoids

Figures & data

Figure 1 Subclasses of flavonoids. Classification is based on variations in the heterocyclic C-ring.

Figure 2 Structures of two glycosides, quercetin-4′-β-glucoside and quercetin-3-β-rutinoside, and a proanthocyanidin trimer C1.

Table 1 Plasma concentrations and kinetics after single-dose administration of flavonoids to humans^a.

Flavonoid	Source	Dose (µmol)	Cmax (µM)	Cmax/Dose (µM/µmol) × 10^3	Tmax (h)	Thalf (h)	References
Flavonols
Quercetin (Q)	Onions	225	0.74	3.3	0.7	28	Hollman et al. (1997)
	Apples	325	0.30	0.9	2.2	23	Hollman et al. (1997)
	Various foods	288	∼0.4	∼1.4	Tmax < 7^b	—	Manach et al. (1998)
Q-3-glucoside	Pure compound	325	5.0	15	0.6	19	Olthof et al. (2000)
Q-4′-gllucoside	Pure compound	331	4.5	14	0.5	19	Olthof et al. (2000)
Q-3-rutinoside	Pure compound	311	0.2	0.6	6.0	28	Hollman et al. (1999)
	Pure compound	662	2.0	3.0	7	7	Graefe et al. (2001)
	Black tea	662	1.0	1.5	4	7	Graefe et al. (2001)
Catechins
(+)-Catechin	Red wine	120	0.09	0.75	1.5	3.1	Donovan et al. (1999)
(−)-Epicatechin	Green tea	143	0.43	3.0	1.3	3.0	Lee et al. (2002)
	Chocolate	565	0.7	1.2	3	—	Richelle et al. (1999)
EGC	Green tea	467	0.73	1.6	1.3	1.7	Lee et al. (2002)
EGCg	Green tea	395	0.17	0.4	1.6	3.4	Lee et al. (2002)
	Green tea	230	0.31	1.3	2	—	Unno et al. (1996)
	Pure compound	284	0.076	0.27	1.6	3.7	Lee et al. (2002)
Proanthocyanidins
Dimer B2	Chocolate	630	0.08	0.1	2	—	Steinberg et al. (2002)
	Chocolate	443	0.04	0.09	2	—	Holt et al. (2002)
Flavanones
Hesperitin-7-rutinoside	Orange juice	727	1.3	1.8	5.8	—	Manach et al. (2003)
Naringin-7-rutinoside	Orange juice	166	0.2	1.2	5.0	—	Manach et al. (2003)
Anthocyanins
Cyanidin-3-rutinoside	Black currant concentrate	137	0.05	0.3	1.5	3.5	Matsumoto et al. (2001)
Delphinidin-3-rutinoside	Black currant concentrate	182	0.07	0.4	1.8	3.2	Matsumoto et al. (2001)
Cyanidin-3-glucoside	Black currant concentrate	24.4	0.005	0.2	1.3	1.3	Matsumoto et al. (2001)
Delphinidin-3-glucoside	Black currant concentrate	68.6	0.02	0.3	1.5	4.2	Matsumoto et al. (2001)
Isoflavones
Genistein	Soy milk	70	0.74	10.6	6.5	—	Xu et al. (1994)
	Pure compound	186	0.87	4.7	7.4	—	Setchell et al. (2003)
Genistein-7-glucoside	Pure compound	62	0.40	6.5	4–6	—	Izumi et al. (2000)
Daidzein	Soy milk	98	0.79	8.1	6.5	—	Xu et al. (1994)
	Pure compound	196	0.92	4.7	7.2	—	Setchell et al. (2003)
Daidzein-7-glucoside	Pure compound	55	0.2	3.6	4–6	—	Izumi et al. (2000)

C_max, peak level; T_max, time to reach peak level; T_half, elimination half life; —, data not given; EGCg, (−)-epigallocatechin gallate; EGC, (−)-epigallocatechin; EGCg, (−)-epicatechin gallate.

^aAdapted from Gonthier (2003).

^bPlasma only sampled at 3, 7, and 20 h after the test meal.

Figure 3 Compartments involved in the metabolism of plant phenols. A flavonoid that is well absorbed in the small intestine (e.g., quercetin-3-glucoside) is chosen as an example. White arrows depict the flow of flavonoids with an intact ring system inside the body. Gray arrows depict the flow of colonic metabolites, the phenolic acids. The width of the arrows indicate the relative importance of these two different classes of metabolites, however, experimental data are still far from complete (Hollman, 2001).

Table 2 Urinary excretion of metabolites with an intact flavonoid structure (as a percentage of the ingested dose) after various flavonoid supplements.

Flavonoid subclass	Excretion (%)	References
Flavonols	0.07–3.6	Hollman et al. (1997); Olthof et al. (2000); de Vries et al. (1998); de Vries et al. (2001)
Catechins	1.1–10	Lee et al. (1995); Donovan et al. (2002); Warden et al. (2001)
Flavanones	4–8	Manach et al. (2003)
Anthocyanins	0.1–5	Felgines et al. (2003); Wu et al. (2002); Matsumoto et al. (2001); Lapidot et al. (1998)
Isoflavones	9–30	Zhang et al. (2003); Xu et al. (1994); Setchell et al. (2003)