Levels Of Flavones Research Articles

Enhancement of flavone levels through overexpression of chalcone isomerase in hairy root cultures of Scutellaria baicalensis

A complementary DNA (cDNA) encoding Scutellaria baicalensis chalcone isomerase (SbCHI) was isolated using rapid amplification of cDNA ends polymerase chain reaction. After the treatment of wounding or methyl jasmonate, SbCHI transcripts were increased in S. baicalensis cell suspensions. SbCHI-overexpressed and SbCH-silenced transgenic hairy root lines were established by using an Agrobacterium rhizogenes-mediated system. SbCHI-overexpressed hairy root lines not only enhanced SbCHI gene expression but also produced more flavones (i.e., baicalin, baicalein, and wogonin) than the control hairy root line. In contrast, SbCHI-silenced hairy root lines reduced SbCHI transcripts and flavone production compared to those of the control hairy roots. In addition, the amount of wogonin in all hairy root cultures was increased compared to that of wild-type roots of S. baicalensis. Finally, this study showed the importance of CHI in flavone biosynthesis and the efficiency of metabolic engineering in S. baicalensis hairy roots.

Polyphenol composition, vitamin C content and antioxidant capacity of Mauritian citrus fruit pulps

The pulp extracts of twenty-one varieties of citrus fruits (oranges, satsumah, clementine, mandarins, tangor, bergamot, lemon, tangelos, kumquat, calamondin and pamplemousses), commonly grown in Mauritius, were characterised in terms of their total soluble solids (TSS), titratable acidity (TA), polyphenol composition and vitamin C contents. Total phenolics ranged from 406.3±14 to 1694±19μgg−1 fresh weight (FW). Total flavonoids varied between 133±6 and 965±7μgg−1 FW and vitamin C contents were from 166±19μg/mL to 677±22μg/mL. The pulp of a pamplemousse variety had the highest TSS/TA ratio whereas lemon pulps had lowest TSS/TA ratios. The antioxidant activities of the pulp extracts were assessed and total phenolics correlated strongly with the trolox equivalent antioxidant capacity (TEAC), ferric reducing antioxidant capacity (FRAP) and hypochlorous acid (HOCl) scavenging activity assays. Based on their antioxidant activities, nine citrus fruits namely, one orange, tangor, kumquat, calamondin and pamplemousse variety and two mandarin and tangelo varieties were further characterised for their flavanone, flavonol and flavone levels by HPLC. Hesperidin (6.89±0.06 to 26.98±0.07mg/g FW) and narirutin (0.27±0.01 and 20.91±0.10mg/g FW) were present at high concentrations compared to the other flavonoid glycosides in the pulp extracts. Naringin was detected only in pulp extracts of pamplemousses. In the light of the data obtained, citrus fruit pulps represent an important source of phytochemicals with potent antioxidant capacity.

Flavonoid composition of lemon-yellow sorghum genotypes

Flavonoid composition of lemon-yellow sorghums grown in two locations in Texas, USA was evaluated and compared with that of white and red sorghums using high performance liquid chromatography (HPLC-PDA). Sorghums from Lubbock were brighter in colour and had minimal weathering compared to those from College Station. Sorghums with red/purple secondary plant colour had the highest levels of 3-deoxyanthocyanidins (8–187μg/g) and their levels were highest in grains from College Station (39–187μg/g). Pericarp colour did not have any effect on 3-deoxyanthocyanidin levels (p>0.05). The tan plant lemon-yellow sorghum Tx2953 had the highest levels of flavones (268–362μg/g). Among the genotypes, lemon-yellow sorghums had the highest levels of flavanones (134–1780μg/g), which are located in the pericarp and their levels were increased in the grains with a bright yellow pericarp and minimal weathering. The high flavanone levels in lemon-yellow sorghums makes this sorghum genotype a good source of those compounds.

Profile of polyphenols and phenolic acids in bracts and receptacles of globe artichoke ( Cynara cardunculus var. scolymus) germplasm

The aim of this work was to assess and quantify polyphenols and hydroxycinnamic acids in different parts of the heads of 6 globe artichoke cultivars by HPLC–DAD–MS/MS. Globe artichoke ( Cynara cardunculus var. scolymus) has been used in folk medicine since Roman times, possibly because of high hydroxycinnamic acid and flavone levels. However, to our knowledge, little is known about how these compounds are distributed in different parts of the artichoke head (outer bracts, inner bracts and receptacle). The phenolic profile was significantly different between cultivars and in different parts of the head, suggesting that individual compounds are accumulated preferentially in specific head parts and cultivars. In particular, the phenolic profile of the outer bracts exhibits very low (443 mg kg −1 dry matter) or zero hydroxycinnamic acid content, and these compounds are present mainly in the receptacle (the edible part; mean value, 1473 mg kg −1 dry matter). This study presents data that indicate the different levels of phenolics in different parts of artichoke, and shows the potential of various artichoke parts as a source of different levels of dietary phenolics.

Bioactive phenolics and antioxidant propensity of flavedo extracts of Mauritian citrus fruits: Potential prophylactic ingredients for functional foods application

The flavedo extracts of twenty-one varieties of citrus fruits (oranges, satsumah, clementine, mandarins, tangor, bergamot, lemon, tangelos, kumquat, calamondin and pamplemousses) grown in Mauritius were examined for their total phenolic, flavonoid and vitamin C contents and antioxidant activities. Total phenolics correlated strongly with the trolox equivalent antioxidant capacity (TEAC), ferric reducing antioxidant capacity (FRAP) and hypochlorous acid (HOCl) scavenging activity assays ( r > 0.85). Based on their antioxidant activities in these three assays nine citrus fruits namely, one orange, clementine, tangor and pamplemousse variety, two tangelo varieties and three mandarin varieties, were further characterized for their flavanone, flavonol and flavone levels by HPLC and their antioxidant activities were assessed by the copper-phenanthroline and iron chelation assays. The flavanone, hesperidin, was present at the highest concentrations in all flavedo extracts except for pamplemousses where it was not detected. Contents in hesperidin ranged from 83 ± 0.06 to 234 ± 1.73 mg/g FW. Poncirin, didymin, diosmin, isorhoifolin and narirutin were also present in all extracts whereas naringin was present only in one mandarin variety. The nine flavedo extracts exhibited good DNA protecting ability in the cuphen assay with IC 50 values ranging from 6.3 ± 0.46 to 23.0 ± 0.48 mg FW/mL. Essentially the flavedos were able to chelate metal ions however, tangor was most effective with an IC 50 value of 9.1 ± 0.08 mg FW/mL. The flavedo extracts of citrus fruits represent a significant source of phenolic antioxidants with potential prophylactic properties for the development of functional foods.

Flavonoid composition of red sorghum genotypes

Abstract The effect of genotype on flavonoid composition was investigated in 13 sorghum varieties using HPLC-DAD. Sorghums with red/purple secondary plant colour had the highest levels of 3-deoxyanthocyanins (32–680 μg/g) with the black pericarp sorghums having the highest. Sorghums with red secondary plant colour had a high proportion of apigeninidin compounds (66–89%), which suggested that secondary plant colour affects 3-deoxyanthocyanin composition. Red pericarp sorghums with tan secondary plant colour had the highest levels of flavones (60–386 μg/g). Flavanones were also detected in all sorghums with a red pericarp (8–48 μg/g) and secondary plant colour did not affect their levels ( p > 0.05). The elevated 3-deoxyanthocyanin levels in the black sorghums were due to their pericarp colour. Black sorghum panicles that were exposed to sunlight during their development had three times more 3-deoxyanthocyanins (617 μg/g) than those that were covered with a paper bag (212 μg/g). This study showed that flavonoid levels and composition were affected by sorghum genotype. This information will help sorghum breeders to produce sorghum genotypes with maximum levels of desired flavonoids.

Robustness of QTLs across germplasm pools using a model quantitative trait

Knowledge of the inheritance of C-glycosyl flavone synthesis in maize (Zea mays L.) silk tissues has been acquired through detailed genetic studies involving primarily germplasm from the Corn Belt Dent race. To test the robustness of this genetic knowledge, we examined C-glycosyl flavone synthesis in a genetically distinct germplasm pool, popcorn. C-glycosyl flavone profiles and levels and the involvement of three specific genes/quantitative trait loci (p, pr1, and sm1) in C-glycosyl flavone synthesis were examined in popcorn germplasm representing at least two races and various diverse geographic regions. Twenty-four inbred lines and 23 hybrids involving these inbred lines and inbred line R17 were characterized for their flavone profiles and levels in silk tissues. Two F2 mapping populations were constructed to examine the involvement of p, pr1, and sm1 on C-glycosyl flavone synthesis. C-glycosyl flavone levels threefold higher than previously reported in Corn Dent Belt materials and a novel class of compounds were discovered. The gene action of sm1 was different, the functional p allele was not always dominant, and pr1 did not affect mays in synthesis. Based on this rather simplistic "model" quantitative trait, it appears that caution should be exercised when attempting to apply quantitative trait locus knowledge accumulated in one germplasm base to a germplasm base that is known to be distinctly unique.

Tissue distribution in mice and metabolism in murine and human liver of apigenin and tricin, flavones with putative cancer chemopreventive properties

The flavones apigenin and tricin, which occur in leafy vegetables and rice bran, respectively, possess cancer chemopreventive properties in preclinical rodent models. Their pharmacology is only poorly understood. We compared their tissue levels in mice in vivo and their metabolism in liver fractions in vitro. Mice received apigenin or tricin (0.2%) with their diet for 5-7 days, and flavone levels were compared in the plasma, liver and gastrointestinal mucosa using HPLC-UV. Flavone metabolism was investigated in murine and human liver microsomes or cytosol in vitro co-incubated with uridine 5'-diphosphoglucuronic acid or 3'-phosphoadenosine-5' phosphosulfate. Flavone metabolites were characterized by on-line HPLC-mass spectrometry. After dietary administration of flavones for 7 days, levels of tricin in plasma, liver and mucosa exceeded those of apigenin by 350, 33 and 100%, respectively. Apigenin was more rapidly glucuronidated than tricin in liver microsomes, whilst tricin underwent swifter sulfonation than apigenin in liver cytosol. For either flavone the rate of glucuronidation was much faster than that of sulfonation. Flavone monoglucuronides and monosulfates were identified as metabolites in microsomal and cytosolic incubations, respectively. When consumed with the diet in mice tricin seems to be more available than apigenin in blood and tissues. Differences in their glucuronidation may account for their differential availability. Thus tricin may have a pharmacokinetic advantage over apigenin. This type of information may help decide which flavonoids to select for clinical development.

Pathway engineering for healthy phytochemicals leading to the production of novel flavonoids in tomato fruit

Flavonoids are a large family of plant polyphenolic secondary metabolites. Although they are widespread throughout the plant kingdom, some flavonoid classes are specific for only a few plant species. Due to their presumed health benefits there is growing interest in the development of food crops with tailor-made levels and composition of flavonoids, designed to exert an optimal biological effect. In order to explore the possibilities of flavonoid engineering in tomato fruits, we have targeted this pathway towards classes of potentially healthy flavonoids which are novel for tomato. Using structural flavonoid genes (encoding stilbene synthase, chalcone synthase, chalcone reductase, chalcone isomerase and flavone synthase) from different plant sources, we were able to produce transgenic tomatoes accumulating new phytochemicals. Biochemical analysis showed that the fruit peel contained high levels of stilbenes (resveratrol and piceid), deoxychalcones (butein and isoliquiritigenin), flavones (luteolin-7-glucoside and luteolin aglycon) and flavonols (quercetin glycosides and kaempferol glycosides). Using an online high-performance liquid chromatography (HPLC) antioxidant detection system, we demonstrated that, due to the presence of the novel flavonoids, the transgenic tomato fruits displayed altered antioxidant profiles. In addition, total antioxidant capacity of tomato fruit peel with high levels of flavones and flavonols increased more than threefold. These results on genetic engineering of flavonoids in tomato fruit demonstrate the possibilities to change the levels and composition of health-related polyphenols in a crop plant and provide more insight in the genetic and biochemical regulation of the flavonoid pathway within this worldwide important vegetable.

Simultaneous Quantification of Adrenergic Amines and Flavonoids in C. aurantium, Various Citrus Species, and Dietary Supplements by Liquid Chromatography

An analytical method was developed for the simultaneous quantitative analysis of 6 amines and 20 flavonoids in fruits and extracts of 30 Citrus species, including C. aurantium, near-Citrus relatives, and dietary supplements by liquid chromatography with photodiode array detection. The separation was achieved with a Phenomenex Synergi Hydro reversed-phase column using gradient mobile phase of sodium acetate buffer (pH 5.5) and acetonitrile. Elution was run at a flow rate of 1.0 mL/min and UV at 254, 280, and 330 nm. Among the amines analyzed, synephrine, the main component, was present in the levels from 0.11 to 2.0 mg/g dry weight in 21 Citrus species and 0.07 to 18.62% in dietary supplements claiming to contain C. aurantium. The flavanones and flavones were analyzed in the same Citrus samples and were species-specific. The levels of flavones were very low compared with those of flavanones. The method facilitated the simultaneous quantification of 6 amines and 20 flavonoids in various Citrus species, the distinction between the different Citrus species, and the analysis of dietary supplements containing C. aurantium.

Two different mutations are involved in the formation of white-flowered gentian plants

Japanese cultivated gentian plants have naturally blue flowers, but some white-flowered cultivars are being bred through the utilization of spontaneous mutants. To determine the molecular basis of white coloration in gentian flowers, we compared two white-flowered cultivars Homoi and Polano White to a blue-flowered cultivar Maciry using biochemical and molecular approaches. High performance liquid chromatography (HPLC) analyses showed that flavone levels in cv. Polano White were only about one-half the amounts measured in the other two cultivars, while anthocyanins were absent in the two white-flowered cultivars compared to cv. Maciry in which high levels accumulated. Northern blot analysis of 10 flavonoid biosynthetic structural genes, previously reported to be temporally regulated in cv. Maciry [1] showed that cv. Homoi lacked transcripts for the anthocyanidin synthase ( ANS) gene while cv. Polano White had decreased expressions for ANS as well as for chalcone synthase ( CHS), flavanone 3-hydroxylase ( F3H), flavonoid 3′,5′-hydroxylase ( F3′,5′H), dihydroflavonol 4-reductase ( DFR), UDP-glucose:flavonoid 3-glucosyltransferase ( 3GT) and anthocyanin 5-aromatic acyltransferase ( 5AT). Southern blot analysis confirmed the deficiency of one of two ANS loci in cv. Homoi. Transient expression of ANS in flower petals also strongly suggested that white flowers of cv. Homoi were derived from ANS mutation. Furthermore, analysis of stress-induced flower pigmentation suggested that rather than mutations in multiple structural genes being the cause, a defect in one or more regulatory factors controlling the later steps of flavonoid biosynthesis is responsible for white coloration in cv. Polano White.

Estimated phytochemical content of the Dietary Approaches to Stop Hypertension (DASH) diet is higher than in the control study diet

The Dietary Approaches to Stop Hypertension (DASH) diet substantially lowers blood pressure and reduces blood lipid levels. The DASH diet menus were designed to reach beneficial levels of fiber, potassium, magnesium, and calcium, and therefore contain more fruits, vegetables, and whole grains relative to the control menus, and consequently more phytochemicals. Using the US Department of Agriculture food composition databases, the polyphenol, carotenoid, and phytosterol contents of the diets used in the DASH study were estimated. When compared with the control diet, the DASH diet is higher in flavonols, flavanones, flavan-3-ols, β-carotene, β-cryptoxanthin, lycopene, lutein+zeaxanthin, and phytosterols. Flavone levels are similar, whereas isoflavones are present in a small amount in the DASH diet. The roles of these compounds in disease risk reduction are becoming recognized. It therefore is possible that the health benefits of the DASH diet are partially attributable to the phytochemicals and might extend beyond cardiovascular disease risk reduction.

Chemical profiling of Ocimum americanum using external flavonoids

A HPLC survey was undertaken of the external flavonoids in 111 herbarium specimens of Ocimum americanum L. ( O. canum Sims), which were largely collected from their natural habitats throughout Africa and Asia. The purpose of this study was to establish the flavonoid profiles of this species over the full range of its geographic distribution in order to use these for authentication purposes. Six different external flavonoid chemotypes were found. The major chemotype, present in circa 80% of the specimens of both var. americanum and var. pilosum collected throughout the distribution area of the species, was characterised by very high levels of nevadensin, slightly lower levels of salvigenin and much lower levels of up to 15 other external flavones. Of the remaining five chemotypes, two were found in var . americanum and three in var. pilosum. All specimens belonging to these chemotypes were collected in South or East Africa and represented by only a few specimens. These samples contained much smaller levels of flavones than present in the major chemotype of O. americanum and all lacked nevadensin. Xanthomicrol, a compound absent from the main chemotype, was the dominant flavone in two of the minor chemotypes. The external flavonoid profiles found in the six chemotypes of O. americanum were compared with those of O.×citriodorum (11 herbarium specimens studied) and seven other closely related species of Ocimum. The main nevadensin/salvigenin pattern present in O. americanum was also found in O.×citriodorum, O. basilicum and some specimens of O. minimum, but there were strong quantitative differences in external flavonoids among these taxa. The other chemotypes of O. americanum showed some similarities in their external flavone profiles to those found in the closely related East African species O. fischeri, O. forskolei, O. kenyense and O. kilimandscharicum, which occur in the same geographic areas. This suggests that the uncommon chemotypes of O. americanum may have originated by an exchange of genes with other Ocimum species, e.g. by introgressive hybridisation. Despite some similarities in profiles, chemical differences were also found among the species, so that it should be possible to authenticate a large proportion of leaf samples of O. americanum on the basis of external flavonoid profiles.

Rapid Analysis of Polymethoxylated Flavones from Citrus Oils by Supercritical Fluid Chromatography

The analysis of citrus essential oils for their content of polymethoxylated flavones (PMFs) using packed column supercritical fluid chromatography (SFC) is described. Samples of sweet orange and mandarin oil were quantitatively analyzed and the resulting flavone levels compared to the values obtained using liquid chromatography. In addition, milligram quantities of all six individual flavone compounds were isolated from a sample of sweet orange oil. Flavone retention in SFC is explained on the basis of substituent dipolarity. Dipoles were calculated using molecular modeling techniques, and the effects of substituent positions or neighboring dipoles were investigated. It is postulated that steric hindrance plays a role in the retention mechanism.

Anp, a genetic locus controlling organ-specific accumulation of anthocyanins in Phaseolus vulgaris L.

A genetic locus, Anp, controls anthocyanin accumulation in the epidermal cell layers of bean (Phaseo-lus vulgaris L.) pods and pulvini, and in the standard petals of bean flowers. The expression of the Anp-dependent phenotype requires normal purple pigmentation of the hypocotyl and of the cotyledons. In the Anp-deficient bean genotype, La Victoire, the mRNA transcripts of chalcone synthase and chalcone isomerase accumulated to levels comparable to those of the Anp-carrying genotype AFN. The two genotypes had similar amounts of chalcone synthase enzyme in the epidermal cells where anthocyanins are accumulated in AFN, as shown by immunocytolocalization. The genotype La Victoire accumulated low levels of flavones, flavonols and proanthocyanins but absolutely no anthocyanins in the organs in which pigmentation is controlled by Anp. The data indicate that Anp represents a locus involved in the organ-specific expression of the late steps of the anthocyanin pathway.

Heat-Induced Quantitative Changes in Carotenoids and Protochlorophyll Precursors in Zea mays

When etiolated seedlings of Zea mays were heat-stressed at 45°C for 16 hours in darkness and then illuminated at 25°C, the accumulation of carotenes and protochlorophyllide was retarded while that of xanthophylls, flavones and phytol was enhanced. Phytol accumulation was retarded in dark-grown seedlings. It is concluded that the increased xanthophyll and flavone levels contribute to the heat-induced yellowing of leaves, and that the reduced protochlorophyllide and phytol levels account, at least partly, for the retardation in protochlorophyll accumulation previously reported in heat-stressed seedlings.