ABSTRACT
Flavonoids are a diverse group of secondary metabolites and include anthocyanidins, flavonols, flavones, flavanols, flavanones, chalcones, dihydrochalcones, and dihydroflavonols (Treutter, 2001). The flavonoid properties of fruits, vegetables, tea, coffee, and nuts play an important role in plant function by quenching reactive chemical species, particularly oxidative stress (Close and McArthur, 2002). They also appear to be important in maintaining healthy bodies (Hertog et al., 1997). This benefit is derived from the naturally occurring phenolic-derived flavonoids, which have the ability to scavenge free radicals produced during metabolism and reduce oxidative stress that leads to a number of chronic diseases such as heart disease. Antioxidant levels have been measured in rainforest plants by their 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging, ferric reducing activity potential (FRAP) assays and parallel measurement of total phenolic content (TPC) (Lu and Yeap Foo, 2000; Clarke et al., 2013) and this tends to indicate that measurement of total phenols may also be an important indicator of the ability to produce antioxidants. The free radical-scavenging ability of apples for instance tends to increase with the TPC and is correlated with the flavanols catechin and epicatechin, and the chalcones phloridzin and phloretin xyloglucoside, especially “Limoncella” in apple skin (D'Abrosca et al., 2007).
