Flavonoids are a large class of naturally occurring compounds widely present in fruits, vegetables and beverages derived from plants. These molecules have been reported to possess a wide range of activities in the prevention of common diseases, including CHD, cancer, neurodegenerative diseases, gastrointestinal disorders and others. The effects appear to be related to the various biological/pharmacological activities of flavonoids. A large number of publications suggest immunomodulatory and anti-inflammatory properties of these compounds. However, almost all studies are in vitro studies with limited research on animal models and scarce data from human studies. The majority of in vitro research has been carried out with single flavonoids, generally aglycones, at rather supraphysiological concentrations. Few studies have investigated the anti-inflammatory effects of physiologically attainable flavonoid concentrations in healthy subjects, and more epidemiological studies and prospective randomised trials are still required. This review summarises evidence for the effects of fruit and tea flavonoids and their metabolites in inflammation and immunity. Mechanisms of effect are discussed, including those on enzyme function and regulation of gene and protein expression. Animal work is included, and evidence from epidemiological studies and human intervention trials is reviewed. Biological relevance and functional benefits of the reported effects, such as resistance to infection or exercise performance, are also discussed. Flavonoids are biologically active polyphenolic compounds ubiquitously found in fruits, vegetables, nuts and plant-derived beverages, such as tea or wine. The composition of flavonoids in different fruit species varies greatly. Quercetin, kaempferol, myricetin and isorhamnetin are common flavonols, with quercetin being the predominant one. A second flavonoid group in fruits is proanthocyanidins and their monomer units, catechins (procyanidin) or gallocatechins (prodelphinidins), which are the natural substrates of polyphenol oxidases and are, therefore, involved in the browning phenomenon of fruits. The main anthocyanins in fruits are glycosides of different anthocyanidins, mainly cyanidin, that are widespread and commonly contribute to the pigmentation of fruits. Citrus fruits differ in their flavonoid profiles from other fruit species, containing flavanones and flavones (hesperidin and naringenin) that are not common in other fruits (1) . The major polyphenolic constituents present in green tea are epicatechin, epigallocatechin, epicatechin-3-gallate and epigallocatechin-3-gallate. In addition to small amount of catechins, black tea contains thearubigins and theaflavins, which are the polymerised forms of catechin monomers and are the major components formed during enzymatic oxidation and the fermentation process (2) . Flavonoids have been reported to possess a wide range of activities in the prevention of common diseases, including CHD, cancer, neurodegenerative diseases, gastrointestinal disorders ...
