Flavonoid content

It is important to quantify the content of tea infusions when evaluating the intake of flavoiioids from consuming tea. However, the daily consumption of flavonoids from tea is difficult to estimate because values depend on accurate assessment of drinking habits and flavonoid content in teas. 

Each plant tissue tends to have an obviously distinctive profile of flavonoids. The flavonoid content can reach about 0.5% in pollen, 10% in propolis, and about 6 mg/kg in honey. Havonoid aglycones appear to be present only in propolis and honey, while pollen contains flavanols in herosidic forms. The flavonoids in honey and propolis have been identified as flavanones and flavanones/flavanols (Campos et ah, 1990). The antimi-crobially active flavanone pinocembrine was foimd to be a major flavonoid in honey (Bogdanov, 1989). Amiot et ah (1989) studied two blossom and two honeydew Swiss honey samples and foimd that pinocembrine was the main flavonoid. Pinocembrine concentration varied between 2 and 3 mg/kg (Bogdanov, 1989). Berahia et ah (1993) analyzed sunflower honey samples and detected six flavone/flavols, four flavanone/ flavols, and pinocembrin, of which pinocembrin is the main flavonoid. The flavonoids in sunflower honey and propolis were characterized and assessed for their effects on hepatic drug-metabolizing enzymes and benzo [fl]pyrene-DNA adduct formation (Sabatier et ah, 1992 Siess et ah, 1996). 

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

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. 

Total flavonoid content. Quantitative analysis of flavonoids depends on the objective of the study. Colorimetric estimation of total flavonoid content is measured by the aluminum chloride colorimetric assay (Jia and others 1999 Chang and others 2002). The total flavonoid content measured in this way is normally expressed in equivalent values of a standard flavonoid, often catechin or quercetin equivalents. Not all subgroups of flavonoids can be quantified by colorimetric methods however, total anthocyanin content is determined using the pH-differentiation method (Boyles and others 1993). 

Chang CC, Yang MH, Wen HM and Chen JC. 2002. Estimation of total flavonoid content in propolis by two complementary colorimetric methods. J Food Drug Anal 10 178-182. 

Harnly JM, Doherty RF, Beecher GR, Holden JM, Haytowitz DB, Bhagwat SA and Gebhardt SE. 2006. Flavonoid content of US fruits, vegetables, and nuts. J Agric Food Chem 54 9966-9977. 

Jia Z, Tang M and Wu J. 1999. The determination of flavonoid contents in mulberry and their scavenging effects on superoxide radicals. Food Chem 64 555-559. 

Lee SU, Lee JH, Choi SH, Lee JS, Ohnisi-Kameyama M, Kozukue N, Levin CE and Friedman M. 2008. Flavonoid content in fresh, home-processed, and light-exposed onions and in dehydrated commercial onion products. J Agric Food Chem 56(18) 8541—8548. 

It seems that the effect of the induction of phenol-content increment by high oxygen atmospheres is affected also by the exposure time of the product to the given atmosphere (Ayala-Zavala and others 2007). Awad and others found no losses of flavonoids in apples stored under conventional or controlled atmosphere (Awad and others 2000). No changes in the concentration of simple phenols, flavonoids, and anthocyanins were observed for Delicious and Ralls apples held for 4 to 5 months under refrigeration (Ju and others 1996). However, they found a decrease in simple phenols in earlier harvested apples after 3 months of cold storage. However, after 7 days at 20°C storage, phenols and flavonoid content decreased rapidly. 

Irradiation of fresh-cut mangoes improved the antioxidant capacity of the product (Fig. 11.5, II), even when a long exposure could reduce the ascorbic acid and 3-carotene content (Gonzalez-Aguilar and others 2007). This was not proportional to the antioxidant capacity, which was influenced more by total phenols and flavonoid content. It seems that the antioxidant capacity improvement could be an additional factor to give added value in the fresh-cut mango industry. 

As discussed previously, UV-C irradiation increased the phenol and flavonoid content such compounds present high radical-quenching activity by themselves (Robles-Sanchez and others 2007). Few studies have been reported specifically about the effect of UV-C irradiation on antioxidant capacity of treated fruit. However, Fan and others... 

Normal-phase TLC using a silica stationary phase was employed for the optimization of the separation of flavonoid content of Matricariae flos (Chamomilla recutita L. Rauschert). Air-dried and powdered plant material was extracted by refluxing for 10 min with methanol. The suspension was filtered, evaporated and the residue was redissolved in methanol. The mobile phases included in the experiments were 1 = ethyl acetate-methylethylketone-formic acid-water (50 30 10 10, v/v) 2 = ethyl acetate-methanol-water (75 15 10 v/v) 3 = ethyl acetate-formic acid-water (80 10 10, v/v) 4 = ethyl acetate-formic acid-water (100 20 30, v/v) 5 = ethyl acetate-formic acid-acetic acid-water (100 11 11 27, v/v) 6 = n-butanol-acetic acid-water (66 17 17, v/v) 7 = ethyl acetate-methanol-formic acid-water (75 10 5 10, v/v) 8 = ethyl acetate-acetic acid-water (80 10 10, v/v). Development was carried out in the linear ascending mode at... 

The flavonoid content of the tinctures of Calendula officinalis L., Passiflora incarnata L and Silybum marianum (L.) Gaertn. was investigated by HPLC-DAD and HPLC-MS. The anti-inflammatory effect, and the beneficial influence to treat hepatic injuries, tension... 

The flavonoid content of honey has also been frequently investigated by HPLC. Thus, 15 flavonoids were found in the Australian jelly bush honey (Leptospremum polygali-folium), myricetin, luteolin and tricetin being the main constituents. The flavonoid composition of the New Zealand manuka (Leptospermum scoparium) honey differed markedly from the Australian one containing mainly quercetin, isorhamnetin, chrysin and luteolin. The method was proposed for the authenticity test of honey floral origin [162],... 

Another study used RP-HPLC for the determination of quercetin, luteolin, apigenin and kaempferol in honey and various other food products. The amounts of flavonoids found are compiled in Table 2.58. The data demonstrate again that the flavonoid content and profile are highly different in various foods and food products which has to be taken into consideration in the design of special diets [163],... 

Because of the importance of soybean and soybean products in both human and animal nutrition their flavonoid content has been investigated many times. Thus, HPLC-UV and HPLC-MS have been applied for the determination of flavonoids and other phytochemicals in soybean extracts and in onion with and without hydrolysis, lg of onion was homogenized and mixed with 8 ml of methanol-water (8 2, v/v). After 2h the suspension was centrifuged at 4°C and the supernatant injected. Powdered soybean (500 mg) was defatted by 2 X 10 ml of hexane and further treated as the onion sample. Flavonoids were hydrolyzed by mixing 2 ml of extract with 2 ml of 2 M HC1 and heated to 130°C for 2 h. The solution was neutralized with 4 M of NaOH. Separation was performed in an ODS column (125 X 4.6 mm... 

It has been established that the flavonoid content in the ground samples was considerably higher than in the unground ones. It was further stated that the results can be employed for the determination of the daily intake of these compounds [182],... 

In an attempt to influence flavor characteristics, CHS antisense and overexpression constructs were introduced into grapefruit by Agrobacterium tumefaciens [16, 59]. CHS overexpression constructs were shown to lead to morphological abnormalities and frequently to death, while a number of CHS antisense constructs resulted in a statistically significant reduction in flavonoid content in the transgenic plants even though there was a large variation in the flavonoid concentration [16]. 

Koca U (2007) Elevation of the flavonoid content in grapefruit by introducing chalcone isomerase gene via biotechnological methods. Turk J Pharm Sci 4(3) 115-124... 

Moved] Cranberry fruit of Early Black cultivar was fractionated chromatographically and fractions were analyzed for flavonoid content. The effects of the flavonoid fractions and ursolic acid, an abundant triterpenoid in cranberry peel, were assessed in two models of colon cancer and one model of breast cancer. Clonogenic soft agar assays were used to determine the effect of these compounds on tumor colony formation in HCT-116, HT-29 and MCF-7 cells. MTT and trypan blue assays were performed to assess their ability to inhibit tumor cell proliferation. TUNEL assays were performed to assess apop-totic response to the cranberry compounds. The proanthocyanidins inhibited tumor colony formation in HCT-116 and HT-29 cells in a dose-dependent manner, with greater effect on the HCT-116 cell line. Ursolic acid strongly inhibited tumor colony formation in both colon cell lines. These compounds also decreased proliferation in all three tumor cell lines with the HCT-116 cell line most strongly affected. (150 words)... 

Knowledge of the flavonoid content of plant-based foods is paramount to understanding their role in plant physiology and human health. Analytical methods are also important to identify adulteration of beverages, for example. And flavonoids are indispensable markers for chemotaxonomic purposes. 

Before a species is analyzed with respect to its flavonoid content, knowledge about earlier reports on the chemistry and flavonoid distribution within the genus and related species may be of value. The most exhaustive source for such information is Chemical Abstracts, and excellent reviews on structures and distribution of flavanoids have been compiled regularly.Several reviews have recently addressed the general field of flavonoid analysis.Among the earlier reviews in the field, we will particularly recommend consulting Techniques of Flavonoid Identification by Markham and Plant Phenolics by Harborne. References to review articles on specific spectroscopic techniques applied on flavonoids will be cited under the various spectroscopic methods covered in this chapter. Spectroscopic information of importance is also presented in several other chapters in this book. 

Tolonen, A. and Uusitalo, L, Fast screening method for the analysis of total flavonoid content in plants and foodstuffs by high-performance liquid chromatography/electrospray ionization time-of-flight mass spectrometry with polarity switching. Rapid Commun. Mass Spectrom., 18, 3113, 2004. 

El Euch, C. et al.. Expression of antisense chalcone synthase RNA in transgenic hybrid walnut microcuttings. Effect on flavonoid content and rooting ability. Plant Mol Biol, 38, 467, 1998. 

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. 

To ensure compatibility with the Royal Society of Chemistry s food composition tables, predetermined screening procedures were used (Table 4.6), which were derived from those outlined for the nutrient tables." All publications and reports on flavonoid content of foods were subsequently evaluated employing the screening procedures (Table 4.6). In brief, inclusion criteria were (a) randomly selected food items purchased from various commercial outlets during different seasons of the year, (b) food samples prepared using normal domestic... 

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