Bioavailability of flavonoids

Wojcicki J, Gawroska-Szkiarz B, Bieganowski W, Patalan M, Smulski HK, Samochowiec L, Zakrzewski J. (1995). Comparative pharmacokinetics and bioavailability of flavonoid glycosides of Ginkgo biloba after a single oral administration of three formulations to healthy volunteers. Materia Med Polona. 27(4) 141-46. 

Passamonti S, Terdoslavich M, Franca R, Vanzo A, TramerF, Braidot E, Petrussa E, Vianello A (2009) Bioavailability of flavonoids a review of their membrane transport and the function of bilitranslocase in animal and plant organisms. Curr Drug Metab 10 369-394... 

Olthof, M.R., Bioavailability of Flavonoids and Cinnamic Acids and their Effect on Plasma Homocysteine in Humans, PhD Thesis, Wageningen University, 2001. 

It is evident that flavonoid ingestion, either through the diet or as pure compounds or active principles in phytomedicines, results in the presence of these biologically active compounds in the gastrointestinal tract during a certain period of time. Thus, this system can be considered as the first putative target of flavonoid effects, especially if we consider the results obtained from the different studies which deal with the bioavailability of flavonoids, (extensively reviewed by Hollman and Katan [25]). 

Interpretation of the in vivo biological activity of flavonoids from in vitro data requires an understanding of their bioavailability, which includes absorption and metabolism. The bioavailability of flavonoids depends on the chemical structure and whether the molecule is conjugated. Although the apparent bioavailability of flavonoids appears to be highly variable between types of flavonoid, from the very... 

Simultaneous with the in vitro research, reports are appearing from the nutritional and human medical areas focusing on bioavailability of flavonoids and the importance of dietary antioxidants in preventing diseases such as coronary heart disease, cancer, vision deterioration and aging in vivo. When these two approaches meet in the hopefully not-too-distant future, the results should reveal scientifically sound conclusions regarding the health benefits of flavonoids. Although there is still much to be learned, there are indications that the scientific approach may reaffirm the basis for many of the remedies known from traditional therapeutic use of grape and berry products in folk medicine. 

The determinaton of the human bioavailability of flavonoids and hydroxy derivatives of cinnamic acid, such as coumaric (26), caffeic (25), chlorogenic (95) and ferulic (69) acids, was carried out by HPLC analysis of urine . 

Rice-Evans C, Spencer JP, Schroeter H, Rechner AR. Bioavailability of flavonoids and potential bioactive forms in vivo. Drug Metabol Drug Interact 2000 17(1-4) 291-310. 

The ubiquitous flavonoids may be cited as an example of the manifold factors affecting the bioavailability of phytochemicals thus, the bioavailability of flavonoids differs between food sources, predominantly due to the nature of the attached sugar(s). The chemical structure (glycoside or aglycone) of a phytochemical will affect intestinal absorption and first-pass metabolism and will, therefore, modulate its pharmacokinetics [4,6]. 

Hu, M., Commentary Bioavailability of flavonoids and polyphenols Call to arms. Molecular Pharmaceutics (2007) 4, 803-806. 

Holbnan PCH (1997) Bioavailability of flavonoids. Eur J Clin Nutr 5LS66-S69 Aggarwal BB, Bhardwaj A, Aggarwal RS, Seeram NP, Shishodia S, Takada Y (2004) Role of resveratrol in prevention and therapy of cancer preclinical and clinical studies. Anticancer Research 24(5A) 2783-2840... 

Understanding the Bioavailability of Flavonoids Through Studies in Caco-2 Cells... 

In this chapter, the phenolic composition and content of regularly consumed fruits and vegetables are extensively discussed through the analysis of the current relevant literature, in order to provide a comprehensive summary of the current compositional and quantitative data on some flavonoid-rich foods. Furthermore, the formal relation of the in vitro antioxidant potential of these fruits and vegetables to the quality of the phenolic and, to a lesser extent, vitamin C content is emphasized. The potential for antioxidant activity of flavonoid-rich fruits and vegetables in vivo is also discussed. The data described here allow identification of the potentially most effective fruits and vegetables in terms of phenolic content and antioxidant activity. However, much research is still needed the elucidation of the metabolism and bioavailability of flavonoids in vivo, as well as of the amounts and the forms in which they are taken up into cells and tissues, is cmcial in order to establish the mechanisms and the forms in which dietary phenolics may act in vivo [58]. Finally, it... 

Hollman PCH. Bioavailability of flavonoids. Eur J Clin Nutr 1997 51(suppl 1) S66-S69. 

To gain a better understanding of the various factors affecting the bioavailability of flavonoids, there have been two general approaches (1) isolated rodent intestinal preparations and (2) human intestinal cell culture using Caco-2 cells. The first of ffiese approaches has many proponents and has yielded much information about mechanisms of transport as well as metabolism [12-18]. As these experiments are done with rat or other rodent tissues, the relevance of the information obtained wifli fliis system to the human may, however, sometimes be questionable. 

Another approach to obtain a better understanding of the bioavailability of flavonoids and their absorption and metabolism in the small intestine has used cultured human caco-2 cells (see Chap. 13). 

Human intervention studies are ultimately necessary to determine the bioavailability of flavonoids from specific foods. A summary of recent studies including the doses, maximal plasma concentrations, and urinary excretion is shown in Table 2. There are large differences in the reported plasma levels among studies using seemingly similar food sources. The large interstudy variability cannot be explained by the doses used but may be explained by differences in experimental conditions and analytical methodology. 

Until recently, the extent of absorption and bioavailability of flavonoids was somewhat unclear. Studies with ileostomy patients have shown that humans can absorb significant amounts of quercetin and that glycosides can be absorbed from the small intestine. Absorption of quercetin glucosides was... 

---