Flavonoids databases

Source information was collected from the USDA Flavonoids database Release 2.1 Kawaii and others 1999, Zhao and others 2005, Tsao and others 2003, Lee and others 2007. 

The total and individual flavonoid contents in commonly consumed fruits and vegetables can be found in several recent surveys of the literature (Arabbi and others 2004 Franke and others 2004 Chun and others 2005 Harnly and others 2006 Sun and Powers 2007). They have been collected and compiled into a database (USDA Flavonoids Database Release 2.1, 2007). Table 5.1 enlists some of the most typical flavonoids, found in the major subgroups just discussed, for selected popular fruits and vegetables based on this database and current literature. 

Flavanones In some cases, flavanones produced by CHI will accumulate to sizeable amounts instead of being diverted away to form flavonols, anthocyanins, and flavanols (see Fig. 5.4). These flavanone products, hesperetin and naringenin being the most common, are frequently encountered in citrus fruits and juices (USDA Flavonoids Database Release 2.1,2007). In most of these cases, essentially no flavonols or anthocyanins are encountered the flavonoid pathway is essentially blocked at the F3H step. 

USDA Flavonoids Database, Release 2.1. 2007. http //www.ars.usda.gov/nutrientdata... 

Consequently, the aims in this chapter are to critically examine the available literature on the flavonoid composition of foods and to establish a food flavonoid database, which can be continually expanded as more information becomes available. By using predetermined selection criteria to ensure critical assessment of data quality, the intention is to provide researchers with an improved resource for use in studies exploring the relationships between flavonoid intake and health as well as highlighting important food groups where flavonoid content data are currently lacking. 

FIGURE 4.1 Schematic of selection and evaluation processes used to compile the flavonoid database. 

Estimation of Scottish Dietary Flavonoid Intake Using the New Comprehensive Flavonoid Database... 

The flavonoid database described in this chapter was applied to 4-day weighed food records obtained from healthy Scottish men n = 41) and women ( = 52) to provide a provisional estimate of flavonoid intake in Scotland. All subjects consumed foods containing flavonols, procyanidins, and catechins, dietary intakes of which are given in Table 4.15. The main flavonol consumed was quercetin, accounting for 66 and 63% of the total flavonol intake of 18.8 mg/day. Primary sources of flavonols were from black tea (42.7%), onions (14.3%), apples (10.2%i), and lager (7.2%i) (Table 4.16). 

Compilation of this flavonoid database could not have taken place without funding from the Scottish Executive Environment and Rural Affairs Department (SEERAD), the Ministry of Agriculture Fisheries and Food, UK, and the EU Framework V Programme. We are also grateful to Dr Geraldine McNeil for much needed help and advice. 

US Department of Agriculture. 2007a. USDA database for the flavonoid content of selected foods. Beltsville, MD USDA. 

The 4-coumarate CoA ligase (4CL EC 6.2.1.12) enzyme activates 4-coumaric acid, caffeic acid, ferrulic acid, and (in some cases) sinapic acid by the formation of CoA esters that serve as branch-point metabolites between the phenylpropanoid pathway and the synthesis of secondary metabolites [46, 47]. The reaction has an absolute requirement for Mg " and ATP as cofactors. Multiple isozymes are present in all plants where it has been studied, some of which have variable substrate specificities consistent with a potential role in controlling accumulation of secondary metabolite end-products. Examination of a navel orange EST database (CitEST) for flavonoid biosynthetic genes resulted in the identification of 10 tentative consensus sequences that potentially represent a multi-enzyme family [29]. Eurther biochemical characterization will be necessary to establish whether these genes have 4CL activity and, if so, whether preferential substrate usage is observed. 

The key role of CHS in flavonoid biosynthesis has made it a focus of research for many years, and it is now very well characterized. The isolation of a cDNA for CHS represented the first gene cloned for a flavonoid enzyme. CHS sequences, and a series of C//S -like sequences, have now been characterized from many species, and Austin and Noel have identified close to 650 C//S -like sequences in public databases. 

To ensure comprehensive coverage of foods and relevant flavonoids, compilation of the flavonoid composition database followed a preset development profile (Figure 4.1). This was a multistage process that evolved from a review of two major food composition data-bases" and from other early stage nutrient bases such as those for vitamin and... 

To ensure coverage of a broad spectrum of journals containing both original and review articles, bibliography databases, such as CAB abstracts, BIDS ISI and Embase, Medline and Current Contents Agriculture and Food Citation index, were searched. Terms used for all database searches were kept simple to limit the risk of missing any original publications (Table 4.5). Initially, each flavonoid subclass was entered and then cross-searched with the... 

The database (Table 4.9-Table 4.12) currently contains entries for 35 types of fruits, 31 vegetables, 26 beverages, eight different jams, three types of chocolate, and 12 herbs. Data are presented as average, minimum, and maximum values (mg/100 g) for each of the flavonoid... 

The data in Table 4.9 Table 4.12 are comprehensive estimates of five classes of flavonoids in commonly available foods in the United Kingdom. Moreover, these estimates are derived from critically assessed published sources and the evaluation procedures adopted ensured the inclusion of content values for edible parts of plant materials available to the UK consumer. A USDA compiled database (http //www.nal.usda.gov/fnic/foodcomp/Data/Flav/flav.pdf) aimed primarily at the North American diet is also available. These databases are in contrast to another literature-derived database that is available for flavonoids where data quality was not formally assessed and flavonoid values determined using semiquantitative methods were also included. 

However, other factors affecting flavonoid levels such as analytical variations, environmental factors, species characteristics, and the effects of processing and storage are more difficult to take into account when compiling the database. 

Despite these caveats, the database constructed in the present study is a comprehensive assessment of the currently available data on the flavonoid contents of foods. 

A comprehensive and critical review of food flavonoid literature has led to the development of a food composition database for flavonols, flavones, procyanidins, catechins, and flava-nones. This database can now be used and continuously updated to estimate flavonoid intake of populations, to identify dietary sources of flavonoids, and to assess associations between flavonoid intake and disease. However, there is a need for better food composition data for flavones, procyanidins, and flavanones as current literature is sparse particularly for citrus fruits, fruit juices, and herbs. In addition, anthocyanin food composition data are lacking although validated methods of determination are becoming available. 

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