Jumat, 30 November 2012
nicotine
Nicotine is an alkaloid compound found in tobacco plants as a natural insecticide and potential replacement for synthetic insecticides. Nicotine has biodegradable properties by natural factors so that does not leave a residue on the host plant. Isolation of nicotine can be done by maceration technique and followed by solvent extraction using chloroform. Isolation technique is quite simple and can produce isolates that contain nicotine in concentrations large enough and relatively unspoiled. The purpose of this study was to determine the time and the optimum volume for isolate maceration nicotine than 50 grams of dried tobacco leaves and to know pengruh rough isolates nicotine as natural insecticides against armyworms (Spodoptera litura).
NICOTINE
Tobacco production are abundant in Indonesia only useful as the tobacco industry are extremely negative impact on human health. Tobacco contains the alkaloid nicotine is bad for human health is also highly toxic to insects that nicotine can be used by humans As with the rice stem borer insecticide.
In this research, isolation of nicotine from tobacco leaves dried soxhletasi by using methanol and then do the salting with acid and alkaline extraction of alkaloids with. The extract obtained was then purified by TLC, and column chromatography. After it was analyzed using IR, UV, and GC-MS. Other tobacco extracts tested for its effectiveness as an insecticide rice stem borers by spraying the rice seedbed with various concentrations.
From the results of TLC analysis using prices obtained methanol solution developers Rf = 0.725. IR spectra analysis results indicate a tertiary aromatic amine, methyl, tertiary amine alifatis and aromatic CH bonds. The results of GC-MS chromatograms showed nicotine compounds appear at the top of the retention time = 9.245 s and 63% similarity index, this suggests that the tobacco alkaloid nicotine contained. Results from UV spectrophotometers generate maximum wavelength 206 nm indicating kearomatisan of pyridine ring in nicotine. Tobacco extracts are used to test the effectiveness of the rice stem borer, rice plants by spraying in which there is the rice stem borer, obtained Fhitung = 19,061 and F table = 3.48. Because Ftabel <Fhitung then Ho is rejected and Ha accepted, the concentration of tobacco leaf extracts affect its effectiveness as an insecticide rice stem borer.
In this research, isolation of nicotine from tobacco leaves dried soxhletasi by using methanol and then do the salting with acid and alkaline extraction of alkaloids with. The extract obtained was then purified by TLC, and column chromatography. After it was analyzed using IR, UV, and GC-MS. Other tobacco extracts tested for its effectiveness as an insecticide rice stem borers by spraying the rice seedbed with various concentrations.
From the results of TLC analysis using prices obtained methanol solution developers Rf = 0.725. IR spectra analysis results indicate a tertiary aromatic amine, methyl, tertiary amine alifatis and aromatic CH bonds. The results of GC-MS chromatograms showed nicotine compounds appear at the top of the retention time = 9.245 s and 63% similarity index, this suggests that the tobacco alkaloid nicotine contained. Results from UV spectrophotometers generate maximum wavelength 206 nm indicating kearomatisan of pyridine ring in nicotine. Tobacco extracts are used to test the effectiveness of the rice stem borer, rice plants by spraying in which there is the rice stem borer, obtained Fhitung = 19,061 and F table = 3.48. Because Ftabel <Fhitung then Ho is rejected and Ha accepted, the concentration of tobacco leaf extracts affect its effectiveness as an insecticide rice stem borer.
Minggu, 25 November 2012
MID SEMESTERS EXAM ANSWERS CHEMISTRY OF NATURAL PRODUCTS
NAME : DESI FEBRIANTI
NIM : RSA1C110011
For example: the ant nest
The results of the study on the color reaction test showed that the extract contains phenols, polyphenols, tannins and flavonoids. TLC test showed positive extract contains tannins and flavonoids. Antibacterial test method used in this study by measuring the clear zone pitting caused by the ethanol extract of tubers anthill with a concentration of 10%, 20%, 30%, 40%, and 50%. Positive controls used were ciprofloxacin 50ppm and negative controls were: DMSO. The results showed that the average diameter of clear zone obtained from the concentration of 10% to 50% is 1.540 cm, 1.752 cm, 1.945 cm, 2.033 cm and 2.076 cm. Research data obtained was analyzed by using the non-parametric Anova test krusskal-wallis test and Mann-Whitney test. The results of this study concluded that ethanol extract of tuber anthill has antibacterial activity against Staphylococcus aureus ATCC 25923 growth and there is a power difference between the concentration of antibacterial extract given.
2. In nature there are many chemical compounds that have benefits for humans, especially as drugs but sometimes the presence of these compounds is very limited so the chemist and pharmacy trying to make a clone of the compound in the laboratory in which we are familiar with the term synthesis. One example is the compound kalkon:
Kalkon is one of a group of flavonoids that are very limited distribution in nature and is found only in a few groups of plants in small amounts. On the other hand, this kalkon compounds have useful biological activities, such as antioxidant, anti-inflammatory and antibacterial properties, so it needs an effort to get kalkon compounds by synthesis. From several studies suggest that group-containing compound kalkon methylenedioxy (-O-CH2-O-) have activity as an antibacterial, so in this study will be the synthesis of compounds derived kalkon with piperonal and Acetophenone. Synthesis of 3,4-metilendioksikalkon through Claisen-Schmidt condensation reaction between piperonal and Acetophenone using NaOH catalyst with various Concentrations of NaOH catalyst is added at 40%, 50%, 60%, 70% and 80%. Results extracted using methylene chloride and then the solvent is evaporated using a rotary evaporator. The next stage characterization of physical properties of synthetic products and their structures analyzed using a spectrophotometer UV-Vis and FT-IR. After that tested the antibacterial activity against bacteria E. coli and S. aureus. Compounds synthesized solid form, is yellow and has a melting point of 80-85 ° C. UV-Vis Data converting the presence of two peaks, namely at λ 264 nm roomates is the absorption of benzoyl and λ 358 nm is the absorption sinamoil roomates. Data shows IR absorption spectra of the carbonyl group (C = O) at wavenumber 1658.7 cm-1, C = C aromatic absorption at wavenumber 1589.2 cm-1 and absorption at wavenumber 2923.9 cm-1 shows vibrational Csp3-H of methylene group (CH2 ). From these data it can be concluded that the compound 3,4-metilendioksikalkon been formed. Highest Yield of 72.58% was obtained at a concentration of 70% NaOH. From the results of the antibacterial test, the greatest inhibition zone Occurs at Concentrations of 3% roomates is 3 mm against E. coli and 2.5 mm against S. aureus.
3. Determination of the principal rules of the solvent compounds is a natural material choice of solvent to be used in the extraction process. Principles underlying the selection of a solvent in the extraction process is a rule of "like dissolve like ', polar compounds roomates means should be analyzed together with polar solvents. Extraction is generally performed for the separation of the laboratories, such as the separation of organic compounds (organic phase) of the aqueous solution (water phase) by using a solvent is not miscible roomates (Harvey 2000).
In the selection of the solvent to be used, be aware of the nature of chemical Constituents (metabolites) to be extracted. Important property is polar and polar groups on the compound to be extracted as an OH group, COOH, as well as other functional groups. By knowing the nature of the metabolites be extracted, it can Easily be selected a suitable solvent by polar metabolites and solvents. Polar compounds dissolve in polar solvents and non-polar compounds dissolve in non-polar solvents. In general, the extraction is done in a row starting with non-polar solvents (hexane or benzene) and a semi-polar solvents (ethyl acetate or diethyl ether), and then with a polar solvent (methanol or ethanol). Would thus obtained crude extract containing consecutive non-polar compounds, semi-polar and polar compounds (Hostetmann et al. 1997). Extraction with non-polar solvents Usually required for the removal of fat before it is extracted with a suitable solvent. Thus, the extracts be obtained free of fat (Harborne 1996).
For example:
1) material flavonoid compounds from plants that are commonly used polar solvents such as ethanol and methanol. Flavonoids are compounds that will dissolve in the polar solvent methanol and ethanol Because it has the same polarity properties. In addition to soluble polar, several flavonoid compounds are also known to be separated by semi-polar solvent. Likely this is due to the nature of polar compounds roomates growing niche to dissolve in polar solvents with higher levels lower
2) alkaloids, caffeine such as coffee powder dissolved in diethyl ether is non-polar Because so as to dissolve the caffeine roomates is also non-polar, but is also due to the low boiling point of chloroform. Because if the high boiling point solvent means possible to approach the boiling point of caffeine can lead to caffeine obtained crystals evaporate so little. With a low boiling point solvent, allowing it to evaporate only kloroformnya.
3) terpenoids soluble organic compounds such as ethers and alcohols.
4) Steroids have semipolar properties can be extracted with chloroform. Moreover, it can also by fat solvents such as ether, benzene, carbontetrachlorida, xylene and alcohol.
4. Examples of compounds of structural determination of caffeine, can be done with infrared spectroscopy. To produce the following data:
With infrared spectroscopy, the structure of caffeine contained in the sample can be determined, ie the typical absorption data from multiple functional groups, or with menbandingkan with standard IR spectrum of caffeine. From the results, it can spektorskopi diketahhui compound structure through cluster-Sugus functions contained therein.
Kamis, 01 November 2012
Cholesterol
Cholesterol, from the Greek chole- (bile) and stereos (solid) followed by the chemical suffix -ol for an alcohol, is an organic chemical substance classified as a waxy steroid of fat. It is an essential structural component of mammalian cell membranes and is required to establish proper membrane permeability and fluidity.
In addition to its importance within cells, cholesterol also serves as a precursor for the biosynthesis of steroid hormones, bile acids, and vitamin D. Cholesterol is the principal sterol synthesized by animals; in vertebrates it is formed predominantly in the liver. Small quantities are synthesized in other cellular organisms (eukaryotes) such as plants and fungi. It is almost completely absent among prokaryotes (i.e., bacteria).
Although cholesterol is important and necessary for human health, high levels of cholesterol in the blood have been linked to damage to arteries and cardiovascular disease.
François Poulletier de la Salle first identified cholesterol in solid form in gallstones, in 1769. However, it was only in 1815 that chemist Eugène Chevreul named the compound "cholesterine"
Physiology
Since cholesterol is essential for all animal life, each cell synthesizes it from simpler molecules, a complex 37-step process which starts with the intracellular protein enzyme HMG-CoA reductase. However, normal and especially high levels of fats (including cholesterol) within the blood circulation, depending on how it is transported within lipoproteins, are strongly associated with progression of atherosclerosis.
For a person of about 68 kg (150 pounds), typical total body-cholesterol synthesis is about 1 g (1,000 mg) per day, and total body content is about 35 g, primarily located within all the membranes of all the cells of the body. Typical daily dietary intake of additional cholesterol, in the United States, is 200–300 mg.
However, most ingested cholesterol is esterified and esterified cholesterol is poorly absorbed. The body also compensates for any absorption of additional cholesterol by reducing cholesterol synthesis. For these reasons, cholesterol intake in food has little, if any, effect on total body cholesterol content or concentrations of cholesterol in the blood.
Cholesterol is recycled. The liver excretes it in a non-esterified form (via bile) into the digestive tract. Typically about 50% of the excreted cholesterol is reabsorbed by the small bowel back into the bloodstream.
Some plants make cholesterol in very small amounts. Plants manufacture phytosterols (substances chemically similar to cholesterol produced within plants), which can compete with cholesterol for reabsorption in the intestinal tract, thus potentially reducing cholesterol reabsorption. However, phytosterols are foreign to animal cells and, if absorbed, accelerate the progression of atherosclerosis. When intestinal lining cells absorb phytosterols, in place of cholesterol, they usually excrete the phytosterol molecules back into the GI tract, an important protective mechanism.
Biosynthesis
All animal cells manufacture cholesterol with relative production rates varying by cell type and organ function. About 20–25% of total daily cholesterol production occurs in the liver; other sites of higher synthesis rates include the intestines, adrenal glands, and reproductive organs. Synthesis within the body starts with one molecule of acetyl CoA and one molecule of acetoacetyl-CoA, which are hydrated to form 3-hydroxy-3-methylglutaryl CoA (HMG-CoA). This molecule is then reduced to mevalonate by the enzyme HMG-CoA reductase. This step is the regulated, rate-limiting and irreversible step in cholesterol synthesis and is the site of action for the statin drugs (HMG-CoA reductase competitive inhibitors).
Mevalonate is then converted to 3-isopentenyl pyrophosphate in three reactions that require ATP. Mevalonate is decarboxylated to isopentenyl pyrophosphate, which is a key metabolite for various biological reactions. Three molecules of isopentenyl pyrophosphate condense to form farnesyl pyrophosphate through the action of geranyl transferase. Two molecules of farnesyl pyrophosphate then condense to form squalene by the action of squalene synthase in the endoplasmic reticulum. Oxidosqualene cyclase then cyclizes squalene to form lanosterol. Finally, lanosterol is then converted to cholesterol.
Konrad Bloch and Feodor Lynen shared the Nobel Prize in Physiology or Medicine in 1964 for their discoveries concerning the mechanism and regulation of cholesterol and fatty acid metabolism.
Jumat, 19 Oktober 2012
biosynthesis of flavonoids
Abstract
Kalkon is one of a group of flavonoids that are very limited distribution in nature and is found only in a few groups of plants in small amounts. On the other hand, this kalkon compounds have useful biological activities, such as antioxidant, anti-inflammatory and antibacterial properties, so it needs an effort to get kalkon compounds by synthesis. From several studies suggest that group-containing compound kalkon methylenedioxy (-O-CH2-O-) have activity as an antibacterial, so in this study will be the synthesis of compounds derived kalkon with piperonal and acetophenone. Synthesis of 3,4-metilendioksikalkon through Claisen-Schmidt condensation reaction between piperonal and acetophenone using NaOH catalyst with various concentrations of NaOH catalyst is added at 40%, 50%, 60%, 70% and 80%. Results extracted using methylene chloride and then the solvent is evaporated using a rotary evaporator. The next stage characterization of physical properties of synthetic products and their structures analyzed using a spectrophotometer UV-Vis and FT-IR. After that tested antibacterial activity against bacteria E. coli and S. aureus. Compounds synthesized solid form, is yellow and has a melting point of 80-85 ° C. UV-Vis data converting the presence of two peaks, namely at λ 264 nm which is the absorption of benzoyl and λ 358 nm which is the absorption sinamoil. Data shows IR absorption spectra of the carbonyl group (C = O) at wavenumber 1658.7 cm-1, absorption C = C aromatic at wavenumber 1589.2 cm-1 and absorption at wavenumber 2923.9 cm-1 shows vibrational Csp3-H of methylene group (CH2). From these data it can be concluded that the compound 3,4-metilendioksikalkon been formed. Highest Yield of 72.58% was obtained at a concentration of 70% NaOH. From the results of the antibacterial test, the greatest inhibition zone occurs at concentrations of 3% which is 3 mm against E. coli and 2.5 mm against S. aureus.
Kalkon is one of a group of flavonoids that are very limited distribution in nature and is found only in a few groups of plants in small amounts. On the other hand, this kalkon compounds have useful biological activities, such as antioxidant, anti-inflammatory and antibacterial properties, so it needs an effort to get kalkon compounds by synthesis. From several studies suggest that group-containing compound kalkon methylenedioxy (-O-CH2-O-) have activity as an antibacterial, so in this study will be the synthesis of compounds derived kalkon with piperonal and acetophenone. Synthesis of 3,4-metilendioksikalkon through Claisen-Schmidt condensation reaction between piperonal and acetophenone using NaOH catalyst with various concentrations of NaOH catalyst is added at 40%, 50%, 60%, 70% and 80%. Results extracted using methylene chloride and then the solvent is evaporated using a rotary evaporator. The next stage characterization of physical properties of synthetic products and their structures analyzed using a spectrophotometer UV-Vis and FT-IR. After that tested antibacterial activity against bacteria E. coli and S. aureus. Compounds synthesized solid form, is yellow and has a melting point of 80-85 ° C. UV-Vis data converting the presence of two peaks, namely at λ 264 nm which is the absorption of benzoyl and λ 358 nm which is the absorption sinamoil. Data shows IR absorption spectra of the carbonyl group (C = O) at wavenumber 1658.7 cm-1, absorption C = C aromatic at wavenumber 1589.2 cm-1 and absorption at wavenumber 2923.9 cm-1 shows vibrational Csp3-H of methylene group (CH2). From these data it can be concluded that the compound 3,4-metilendioksikalkon been formed. Highest Yield of 72.58% was obtained at a concentration of 70% NaOH. From the results of the antibacterial test, the greatest inhibition zone occurs at concentrations of 3% which is 3 mm against E. coli and 2.5 mm against S. aureus.
Kamis, 18 Oktober 2012
Flavonoids Biosynthesis
If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Locations of Mapped Genes:
Synonyms: flavonoid biosynthesis
Superclasses: Biosynthesis → Secondary Metabolites Biosynthesis → Phenylpropanoid Derivatives Biosynthesis → Flavonoids Biosynthesis → Chalcones Biosynthesis
Biosynthesis → Secondary Metabolites Biosynthesis → Phenylpropanoid Derivatives Biosynthesis → Flavonoids 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.
Minggu, 07 Oktober 2012
flavonoid
Flavonoids (or bioflavonoids) (from the Latin word flavus meaning yellow, their colour in nature) are a class of plant secondary metabolites.
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.
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.
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