Flavonoids half life

For most flavonoids, the maximum concentration in human plasma occurs 1-6 hours after ingestion with an elimination half-life (t1/2) from 1 to 28 hours.15-21 Therefore, flavonoids can accumulate in the circulation and in tissues with frequently repeated intakes. Plasma quercetin in free-living subjects, measured after overnight fast, is typically 50-80 nmol/L, though smaller values are observed following a low-flavonoid diet.15 Conversely, supplementation with 500 mg/d rutin for 6 weeks increased plasma quercetin to 165 nmol/L22 and to 0.63 and 1.5 prnol/L following supplementation with 80 mg and >1 g quercetin equivalents daily for 7 and 28 days, respectively.23-24... 

Source Flavonoid Tmax (h) Half life (h) Reference... 

A series of flavonoids from the milk thistle, Silybum mar-ianum (Asteraceae) have antihepatotoxic activity. The individually active compounds are silybin (54) (the major compound), silychristin (55), and silydianin (56), collectively called silymarin (Fig. 11.19). Silymarin is used in Germany for treatment of human liver disorders (Vogel, 1976,1982). The elimination half-life of silybin is about 2 h (Beier and Nigg, 1992). 

Although vacuolar HCAs, HBAs and flavonoids are potent antioxidants, their in vivo scavenging capacity has been questioned because they are not present in the compartments with intense ROS production. The largest part of ROS arises from electron leakage to O2 from the electron transport chains of chloroplasts and mitochondria (Asada, 1996 Moller, 2001). They additionally rise from photorespiration in peroxisomes, from apoplastic NADPH oxidases and various cell wall peroxidases. Most ROS are short-lived species (Moller etal, 2007). The mean half-life in plant tissues is estimated to be 1 o,s, 1 ps, 1 ms, and 1 ns, and their estimated traveling distances are of 30 nm, 30 nm, 1 p.m. 

Fig. 3.10. Gymnosperms are endowed with a sole type of O-methyltransferase. This was shown to act exclusively on the 3 -hydroxyl (45). Any additionally hydroxylated flavonoid thus may possess a very short half-life. In angiosperms, other O-methyltransferases direct O-methylation to other hydroxyls, protecting the flavonoids against oxidative degradation...

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