Flavonoids were referred to as Vitamin P (probably due to the effect they had on the permeability of vascular capillaries) from the mid-1930s to early 50s, but the term has since fallen out of use.
According to the IUPAC nomenclature,they can be classified into:
• flavones, derived from 2-phenylchromen-4-one (2-phenyl-1,4-benzopyrone) structure (examples: quercetin, rutin).
• isoflavonoids, derived from 3-phenylchromen-4-one (3-phenyl-1,4-benzopyrone) structure
• neoflavonoids, derived from 4-phenylcoumarine (4-phenyl-1,2-benzopyrone) structure.
Isoflavan structure
Neoflavonoids structure
The three flavonoid classes above are all ketone-containing compounds, and as such, are flavonoids and flavonols. This class was the first to be termed "bioflavonoids." The terms flavonoid and bioflavonoid have also been more loosely used to describe non-ketone polyhydroxy polyphenol compounds which are more specifically termed flavanoids, flavan-3-ols (or catechins).
The three flavonoid classes above are all ketone-containing compounds, and as such, are flavonoids and flavonols. This class was the first to be termed "bioflavonoids." The terms flavonoid and bioflavonoid have also been more loosely used to describe non-ketone polyhydroxy polyphenol compounds which are more specifically termed flavanoids, flavan-3-ols (or catechins).
BIOSYNTHESIS
Summary:
Flavonoids are secondary metabolites formed from phenylpropanoid and fatty acid derivatives and have important functions, acting as UV-B protectors [ Ryan01 ], attractors of pollinators and seed dispersers, insect feeding attractors, anti-feedants, signal molecules in legume-rhizobium bacteria interactions [ Peters86 ], and fungicides. Flavonoids have also received a lot of attention due to their effect of human health. In some plant species, flavonoids are required for fertility, but this is not the case in Arabidopsis [ Burbulis96 ].
Biosynthesis is thought to occur in the cytoplasm through enzymes that are associated with the endoplasmatic reticulum membranes [ Hrazdina87 ] where the enzymes form a large, macromolecular complex [ Burbulis99 ].
The structure of the major flavonoids in Arabidopsis have recently been described [ Veit99 ]. Under greenhouse conditions, only kaempferol glycosides accumulate in Arabidopsis . With higher UV exposure, quercetin metabolites can be detected as well [ Veit99 ]. Most flavonoids accumulate in the vacuole, the cuticular wax and in the cell wall [ Markham00 ].
Flavonoids constitute a relatively diverse family of aromatic molecules that are derived from Phenylalanine and malonyl-coenzyme A (CoA; via the fatty acidic pathway). [ WinkelShir01 ] There are six major subgroups found in most higher plants: the chalcones, flavones, flavonols, flavandiols, anthocyanins, and condensed tannins (proanthocyanidins); a seventh group, the aurones, are not ubiquitos.
Isoflavonoids are found mostly in legumes but also in a small number of non-legume plants and another specialized form of flavonoids, the phlobaphenes (monomers: 3-deoxyanthocyanins), have been detected in only a few species so far. Stilbenes, closely related to flavonoids, are synthesized by yet another group of unrelated species.
FUNCTION OF FLAVONOIDS IN PLANTS
Flavonoids are widely distributed in plants fulfilling many functions.
Flavonoids are the most important plant pigments for flower coloration producing yellow or red/blue pigmentation in petals designed to attract pollinator animals. In higher plants, Flavonoids are involved in UV filtration, symbiotic nitrogen fixation and floral pigmentation. They may act as a chemical messenger or physiological regulator, they can also act as cell cycle inhibitors. Flavonoids secreted by the root of their host plant help Rhizobia in the infection stage of their symbiotic relationship with legumes like peas, beans, clover, and soy. Rhizobia living in soil are able to sense the flavonoids and this triggers the secretion of Nod factors, which in turn are recognized by the host plant and can lead to root hair deformation and several cellular responses such as ion fluxes and the formation of a root nodule. In addition, some flavonoids have inhibitory activity against organisms that cause plant disease e.g. Fusarium oxysporum.
HUMAN HEALTH
Flavonoids (specifically flavanoids such as the catechins) are "the most common group of polyphenolic compounds in the human diet and are found ubiquitously in plants". Flavonols, the original bioflavonoids such as quercetin, are also found ubiquitously, but in lesser quantities.
The widespread distribution of flavonoids, their variety and their relatively low toxicity compared to other active plant compounds (for instance alkaloids) mean that many animals, including humans, ingest significant quantities in their diet. Preliminary research indicates that flavonoids may modify allergens, viruses, and carcinogens, and so may be biological "response modifiers". In vitro studies show that flavonoids also have anti-allergic, anti-inflammatory, anti-microbial, anti-cancer, and anti-diarrheal activities
Antioxidant activity in vitro
Flavonoids (both flavonols and flavanols) are most commonly known for their antioxidant activity in vitro. At high experimental concentrations that would not exist in vivo, the antioxidant abilities of flavonoids in vitro may be stronger than those of vitamin C and E, depending on concentrations tested.
Consumers and food manufacturers have become interested in flavonoids for their possible medicinal properties, especially their putative role in inhibiting cancer or cardiovascular disease. Although physiological evidence is not yet established, the beneficial effects of fruits, vegetables, tea, and red wine have sometimes been attributed to flavonoid compounds.
Negligible antioxidant properties of flavonoids in vivo
A research team at the Linus Pauling Institute and the European Food Safety Authority state that flavonoids, inside the human body, are of little or no direct antioxidant value. Body conditions are unlike controlled test tube conditions, and the flavonoids are poorly absorbed (less than 5%), with most of what is absorbed being quickly metabolized and excreted.
The increase in antioxidant capacity of blood seen after the consumption of flavonoid-rich foods may not be caused directly by the flavonoids themselves, but is probably due to increased production of uric acid resulting from excretion of flavonoids from the body. According to Frei, "we can now follow the activity of flavonoids in the body, and one thing that is clear is that the body sees them as foreign compounds and is trying to get rid of them."
Cancer
Flavonoids might induce mechanisms that affect cancer cells and inhibit tumor invasion. In preliminary studies, UCLA cancer researchers proposed that smokers who ate foods containing certain flavonoids, such as the flavan-3-ols (catechins) found in strawberries and green and black teas, kaempferol from brussel sprouts and apples, and quercetin from beans, onions and apples, may have reduced risk of developing lung cancer
POTENSIAL DELETERIOUS EFFECTS ON HUMAN HEALTH
Carcinogenic potential
Flavonoids were found to be strong topoisomerase inhibitors and induce DNA mutations in the MLL gene, which are common findings in neonatal acute leukemia. The DNA changes were increased by treatment with flavonoids in cultured blood stem cells. In one study, a high flavonoid-content diet in mothers seemed to increase risk of MLL+ acute myeloid leukemia in neonates. This result was not statistically significant though, and when the data on all types of leukiama in the study were taken together, a beneficial effect of the high-flavonoid diet was seen.
Natural phenols (flavonoids in one set of experiments and delphinidin in another ) were found to be strong topoisomerase inhibitors, similar to some chemotherapeutic anticancer drugs including etoposide and doxorubicin. This property may be responsible for both an anticarcinogenic-proapoptotic effect and a carcinogenic, DNA damaging potential of the substances.
EXAMPLE FLAVONOIDS
Quercetin
Flavonoids are secondary metabolites formed from phenylpropanoid and fatty acid derivatives and have important functions, acting as UV-B protectors [ Ryan01 ], attractors of pollinators and seed dispersers, insect feeding attractors, anti-feedants, signal molecules in legume-rhizobium bacteria interactions [ Peters86 ], and fungicides. Flavonoids have also received a lot of attention due to their effect of human health. In some plant species, flavonoids are required for fertility, but this is not the case in Arabidopsis [ Burbulis96 ].
Biosynthesis is thought to occur in the cytoplasm through enzymes that are associated with the endoplasmatic reticulum membranes [ Hrazdina87 ] where the enzymes form a large, macromolecular complex [ Burbulis99 ].
The structure of the major flavonoids in Arabidopsis have recently been described [ Veit99 ]. Under greenhouse conditions, only kaempferol glycosides accumulate in Arabidopsis . With higher UV exposure, quercetin metabolites can be detected as well [ Veit99 ]. Most flavonoids accumulate in the vacuole, the cuticular wax and in the cell wall [ Markham00 ].
Flavonoids constitute a relatively diverse family of aromatic molecules that are derived from Phenylalanine and malonyl-coenzyme A (CoA; via the fatty acidic pathway). [ WinkelShir01 ] There are six major subgroups found in most higher plants: the chalcones, flavones, flavonols, flavandiols, anthocyanins, and condensed tannins (proanthocyanidins); a seventh group, the aurones, are not ubiquitos.
Isoflavonoids are found mostly in legumes but also in a small number of non-legume plants and another specialized form of flavonoids, the phlobaphenes (monomers: 3-deoxyanthocyanins), have been detected in only a few species so far. Stilbenes, closely related to flavonoids, are synthesized by yet another group of unrelated species.
FUNCTION OF FLAVONOIDS IN PLANTS
Flavonoids are widely distributed in plants fulfilling many functions.
Flavonoids are the most important plant pigments for flower coloration producing yellow or red/blue pigmentation in petals designed to attract pollinator animals. In higher plants, Flavonoids are involved in UV filtration, symbiotic nitrogen fixation and floral pigmentation. They may act as a chemical messenger or physiological regulator, they can also act as cell cycle inhibitors. Flavonoids secreted by the root of their host plant help Rhizobia in the infection stage of their symbiotic relationship with legumes like peas, beans, clover, and soy. Rhizobia living in soil are able to sense the flavonoids and this triggers the secretion of Nod factors, which in turn are recognized by the host plant and can lead to root hair deformation and several cellular responses such as ion fluxes and the formation of a root nodule. In addition, some flavonoids have inhibitory activity against organisms that cause plant disease e.g. Fusarium oxysporum.
HUMAN HEALTH
Flavonoids (specifically flavanoids such as the catechins) are "the most common group of polyphenolic compounds in the human diet and are found ubiquitously in plants". Flavonols, the original bioflavonoids such as quercetin, are also found ubiquitously, but in lesser quantities.
The widespread distribution of flavonoids, their variety and their relatively low toxicity compared to other active plant compounds (for instance alkaloids) mean that many animals, including humans, ingest significant quantities in their diet. Preliminary research indicates that flavonoids may modify allergens, viruses, and carcinogens, and so may be biological "response modifiers". In vitro studies show that flavonoids also have anti-allergic, anti-inflammatory, anti-microbial, anti-cancer, and anti-diarrheal activities
Antioxidant activity in vitro
Flavonoids (both flavonols and flavanols) are most commonly known for their antioxidant activity in vitro. At high experimental concentrations that would not exist in vivo, the antioxidant abilities of flavonoids in vitro may be stronger than those of vitamin C and E, depending on concentrations tested.
Consumers and food manufacturers have become interested in flavonoids for their possible medicinal properties, especially their putative role in inhibiting cancer or cardiovascular disease. Although physiological evidence is not yet established, the beneficial effects of fruits, vegetables, tea, and red wine have sometimes been attributed to flavonoid compounds.
Negligible antioxidant properties of flavonoids in vivo
A research team at the Linus Pauling Institute and the European Food Safety Authority state that flavonoids, inside the human body, are of little or no direct antioxidant value. Body conditions are unlike controlled test tube conditions, and the flavonoids are poorly absorbed (less than 5%), with most of what is absorbed being quickly metabolized and excreted.
The increase in antioxidant capacity of blood seen after the consumption of flavonoid-rich foods may not be caused directly by the flavonoids themselves, but is probably due to increased production of uric acid resulting from excretion of flavonoids from the body. According to Frei, "we can now follow the activity of flavonoids in the body, and one thing that is clear is that the body sees them as foreign compounds and is trying to get rid of them."
Cancer
Flavonoids might induce mechanisms that affect cancer cells and inhibit tumor invasion. In preliminary studies, UCLA cancer researchers proposed that smokers who ate foods containing certain flavonoids, such as the flavan-3-ols (catechins) found in strawberries and green and black teas, kaempferol from brussel sprouts and apples, and quercetin from beans, onions and apples, may have reduced risk of developing lung cancer
POTENSIAL DELETERIOUS EFFECTS ON HUMAN HEALTH
Carcinogenic potential
Flavonoids were found to be strong topoisomerase inhibitors and induce DNA mutations in the MLL gene, which are common findings in neonatal acute leukemia. The DNA changes were increased by treatment with flavonoids in cultured blood stem cells. In one study, a high flavonoid-content diet in mothers seemed to increase risk of MLL+ acute myeloid leukemia in neonates. This result was not statistically significant though, and when the data on all types of leukiama in the study were taken together, a beneficial effect of the high-flavonoid diet was seen.
Natural phenols (flavonoids in one set of experiments and delphinidin in another ) were found to be strong topoisomerase inhibitors, similar to some chemotherapeutic anticancer drugs including etoposide and doxorubicin. This property may be responsible for both an anticarcinogenic-proapoptotic effect and a carcinogenic, DNA damaging potential of the substances.
EXAMPLE FLAVONOIDS
Quercetin
Quercetin
Quercetin, a flavonoid and more specifically a flavonol, is the aglycone form of other flavonoid glycosides, such as rutin and quercitrin, found in citrus fruit, buckwheat and onions. Quercetin forms the glycosides, quercitrin and rutin, together with rhamnose and rutinose, respectively.
Although there is preliminary evidence that asthma, lung cancer and breast cancer are lower among people consuming higher dietary levels of quercetin, the U.S. Food and Drug Administration (FDA), EFSA and the American Cancer Society have concluded that no physiological role exists. The American Cancer Society states that dietary quercetin "is unlikely to cause any major problems or benefits."
Epicatechin
Quercetin, a flavonoid and more specifically a flavonol, is the aglycone form of other flavonoid glycosides, such as rutin and quercitrin, found in citrus fruit, buckwheat and onions. Quercetin forms the glycosides, quercitrin and rutin, together with rhamnose and rutinose, respectively.
Although there is preliminary evidence that asthma, lung cancer and breast cancer are lower among people consuming higher dietary levels of quercetin, the U.S. Food and Drug Administration (FDA), EFSA and the American Cancer Society have concluded that no physiological role exists. The American Cancer Society states that dietary quercetin "is unlikely to cause any major problems or benefits."
Epicatechin
Epicatechin (EC)
Epicatechin may improve blood flow and has potential for cardiac health. Cocoa, the major ingredient of dark chocolate, contains relatively high amounts of epicatechin and has been found to have nearly twice the antioxidant content of red wine and up to three times that of green tea in vitro.[27][28] In the test outlined above, it appears the potential antioxidant effects in vivo are minimal as the antioxidants are rapidly excreted from the body.
DIETARY SOURCES
Good sources of flavonoids include all citrus fruits, berries, ginkgo biloba, onions (particularly red onion), parsley, pulses, tea (especially white and green tea), red wine, seabuckthorn, and dark chocolate (with a cocoa content of seventy percent or greater).
Citrus
The citrus bioflavonoids include hesperidin (a glycoside of the flavanone hesperetin), quercitrin, rutin (two glycosides of the flavonol quercetin), and the flavone tangeritin. In addition to possessing in vitro antioxidant activity and an ability to increase intracellular levels of vitamin C, rutin and hesperidin may have beneficial effects on capillary permeability and blood flow. They also exhibit anti-allergy and anti-inflammatory benefits of quercetin from in vitro studies. Quercetin can also inhibit reverse transcriptase, part of the replication process of retroviruses. The therapeutic relevance of this inhibition has not been established.
Tea
Main article: Polyphenols in tea
Wine
See also: Polyphenols in wine
Dark chocolate
Main article: Health effects of chocolate
Flavonoids exist naturally in cacao, but because they can be bitter, they are often removed from chocolate, even dark chocolate. Although flavonoids are present in milk chocolate, milk may interfere with their absorption.
SCIENTISTS WHO WORKED ON FLAVONOIDS
Jeffrey Harborne investigated the role of flavonoids in interactions between plants and insects. He also investigated the relationship between anthocyanins and the ecology of pollination. He has published on chemotaxonomy as in his research articles on the prevention of anthocyanins, flavones and auron in the primrose family (Primulaceae), in snapdragons (Antirrhinum) and a number of other plants. He also published on isoflavones and chemical ecology.
Epicatechin may improve blood flow and has potential for cardiac health. Cocoa, the major ingredient of dark chocolate, contains relatively high amounts of epicatechin and has been found to have nearly twice the antioxidant content of red wine and up to three times that of green tea in vitro.[27][28] In the test outlined above, it appears the potential antioxidant effects in vivo are minimal as the antioxidants are rapidly excreted from the body.
DIETARY SOURCES
Good sources of flavonoids include all citrus fruits, berries, ginkgo biloba, onions (particularly red onion), parsley, pulses, tea (especially white and green tea), red wine, seabuckthorn, and dark chocolate (with a cocoa content of seventy percent or greater).
Citrus
The citrus bioflavonoids include hesperidin (a glycoside of the flavanone hesperetin), quercitrin, rutin (two glycosides of the flavonol quercetin), and the flavone tangeritin. In addition to possessing in vitro antioxidant activity and an ability to increase intracellular levels of vitamin C, rutin and hesperidin may have beneficial effects on capillary permeability and blood flow. They also exhibit anti-allergy and anti-inflammatory benefits of quercetin from in vitro studies. Quercetin can also inhibit reverse transcriptase, part of the replication process of retroviruses. The therapeutic relevance of this inhibition has not been established.
Tea
Main article: Polyphenols in tea
Wine
See also: Polyphenols in wine
Dark chocolate
Main article: Health effects of chocolate
Flavonoids exist naturally in cacao, but because they can be bitter, they are often removed from chocolate, even dark chocolate. Although flavonoids are present in milk chocolate, milk may interfere with their absorption.
SCIENTISTS WHO WORKED ON FLAVONOIDS
Jeffrey Harborne investigated the role of flavonoids in interactions between plants and insects. He also investigated the relationship between anthocyanins and the ecology of pollination. He has published on chemotaxonomy as in his research articles on the prevention of anthocyanins, flavones and auron in the primrose family (Primulaceae), in snapdragons (Antirrhinum) and a number of other plants. He also published on isoflavones and chemical ecology.
hi desi,,
BalasHapusI've read your article
and i found the problem.
, some flavonoids have inhibitory activity against organisms that cause plant disease e.g. Fusarium oxysporum.
how flavonoids can inhibit it?
such as whether inhibiting activity?
please explain desi,
thanks :)
. In F. oxysporum trypsin the specificity pocket is larger than in bovine trypsin. This explains the preference of F. oxysporum trypsin for the bulkier arginine over lysine and the reverse preference in bovine trypsin. The binding cavity on the C-terminal side of the substrate is more restricted in F. oxysporum trypsin than in mammalian and Streptomyces griseus trypsins, which explains the relative inactivity of F. oxysporum trypsin towards
Hapusthanks liza
HapusI'll try to answer your problem
- how the flavonoids to inhibit the organisms that cause plant diseases
Plant roots secrete a signal that activates the expression of genes that play a role in bacterial nodulasi. After the last signal, the bacteria (rhizobia) will synthesize a signal that induces the formation of the nodule meristem and allow bacteria to enter into meristem through the process of infection. Chemical signals in the bacterial synthesis was essentially a modified amino acid (homoserin lactone) that carry varying acyl chain Substituents called acyl homoserin lactone (AHL).
Through the detection of and reaction to the chemical compounds of plant cells individually can feel how much the cells that surround them. Symbiotic interaction is due to the exchange of signals between plants and bacteria (rhizobia). Plants secrete substances that flavonoid phenols group together with NodD (activator protein) from the bacterium induces the expression of genes of rhizobia forming nodules (nod, zero, noe). As a result, the rhizobia produce Nod factors. Nod factors induced response by plants (one of them) with the formation of nodules.
Around the root hairs nuts collected a large number of bacteria Rhizobium either naturally or artificially. Due to accumulation of bacteria, the root hairs will issue triftopan, which is converted into indole acetic bacteria. The presence of indo acetate causes hair roots to be menkerut and bacteria also produce enzymes that can dissolve pektat compounds contained in vibril (cellulose) pelts root, so that bacteria can attach to reed roots
- inhibits the activity by Fusarium oxysporum
fungus Fusarium oxysporum fusarat also produces acid. Fusarat acid can inhibit the growth of callus and shoots. This is presumably due to disruption of cell membrane permeability, inhibition of cytochrome oxidation and respiration in mitochondria thereby inhibiting the synthesis of ATP, and decreased activity of phenol (Purwati, et al. 2007).
According to Waggoner and Dimond in Semangun (2001), Fusarium oxysporum produces enzymes pektolitik, terutaman pectin-methyl-esterase (PME) and depolimerase (DP). PME reduce etal of pectin chains and produce acids pektat. DP broke into poligalakturonida pektat acid chain with a different weight molekul.enzim these materials break down pectin in the cell walls of xylem vessels and xylem parenchyma pectin on.
Solving pectin of the cell wall material resulting in loss of cell rigidity so the plants wither. Pektat acid fragments into the xylem vessels and shape the colloidal material that may menggandung nonpektin and can clog arteries. Blockage by pektat acid fragments may hinder the delivery of water and soil nutrients.
This situation resulted in plants experiencing water shortages, especially when high transpiration rate. Water shortages lead to decreased cell turgor pressure and make the plant wilt. If not resolved soon, the plant will have a permanent wilt and die (Sarna et al, 2007).
guys,,
BalasHapusCan you find a solution to my problem
how the role of flavonoids in the interaction of plants and insects?
hy desi, i want to try answer your problem,,
HapusMost flavonoids function essential for plants to survive, such as towing for insects to aid pollination and seed dispersal, stimulants Rhizobium for nitrogen fixation and nutrient resorption for leaf formation. Besides flavonoids play a role in helping plants survive in suboptimal conditions,
hopefully this can help your problem, may be our friends can give other suggestions. thank's
how flavonoid induce mechanisms that affect cancer cells and inhibit tumor invasion ??
BalasHapusFotsis et al. reported that certain flavonoids are potent inhibitors of various human normal
Hapusand cancer cell lines in the low micromolar range. Luteolin was effective in all cell lines and was among the most potent inhibitors (IC50 concentrations between 1.1 μM and 7.6 μM) together with hydroxyflavone, 3',4'-dihydroxyflavone, 2',3'-dihydroxyflavone, fisetin, and apigenin. Thus, luteolin and some other flavonoids might be able to stop the development of solid tumors by suppressing angiogenesis.
Cherng et al. determined the inhibitory effect of 10 minor dietary constituents (e.g.baicalein,
linalool, caffeic acid, ferulic acid) on proliferation in human cancer cell lines from 10 different organs, and in normal leucocytes. Luteolin was effective in all 10 cancer types, with lowest IC50 for carcinoma of the stomach (25 μM), cervix (27 μM), lung (41 μM) and bladder (68 μM). Baicalein had a narrower spectrum, but was partly more specific (ratio of inhibitory concentration in cancer to normal cells). Most other compounds were ineffective, but linalool, a monoterpene, had a low IC50 of 1 μM and extremely high specificity in cervix cancer cells.
Takahashi et al. found luteolin and apigenin to strongly inhibit growth of HL60 human leukemia cells and to induce morphological differentiation into granulocytes, while quercetin, naringenin, galangin and kaempferol also caused inhibition but not morphological differentiation.
6-Hydroxykaempferol 3,6-diglucoside is a flavonoid compound isolated and purified from the herbs of Chrysactinia tinctorius. It shows weak inhibitory effects on the adenosine 5'-diphosphate (ADP)- induced platelet aggregation. 6-Hydroxykaempferol 3,6-diglucoside
BalasHapus