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PubMed1999

Comparative analysis of the effects of flavonoids on proliferation, cytotoxicity, and apoptosis in human colon cancer cell lines.

Flavonoids are polyphenolic compounds that occur ubiquitously in foods of plant origin. Their proposed protective role in tumor development may prevail especially in the intestinal tract due to direct exposure of intestinal epithelia to these dietary ingredients. We have screened more than 30 flavonoids for their effects on cell proliferation and potential cytotoxicity in the human colon cancer cell lines Caco-2, displaying features of small intestinal epithelial cells, and HT-29, resembling colonic crypt cells. In addition, for selected compounds we assessed whether they induce apoptosis by determining caspase-3 activation. Studies on the dose dependent effects of the flavonoids showed antiproliferative activity of all compounds with EC50 values ranging between 39.7 +/- 2.3 microM (baicalein) and 203.6 +/- 15.5 microM (diosmin). In almost all cases, growth inhibition by the flavonoids occurred in the absence of cytotoxicity. There was no obvious structure-activity relationship in the antiproliferative effects either on basis of the subclasses (i.e., isoflavones, flavones, flavonols, flavonones) or with respect to kind or position of substituents within a class. In a subset of experiments we examined the antiproliferative activities of the most potent compound of each flavonoid subgroup in addition in LLC-PK1, a renal tubular cell line, and the human breast cancer cell line MCF-7. Out of four flavonols tested, three displayed almost equal antiproliferative activities in all cell lines but fisetin was less potent in MCF-7 cells. The flavanones bavachinin and flavanone inhibited growth of Caco-2 and HT-29 cells with lower EC50 values than that obtained in LLC-PK1 and MCF-7 cells. The lower susceptibility of LLC-PK1 and MCF-7 cells towards growth arrest was even more pronounced in the case of the flavone baicalein. Half maximal growth-inhibition in LLC-PK1 and MCF-7 required 2.5 and 6.6 fold higher concentrations than that needed in the intestinal cell lines. The flavonoids failed to affect apoptosis in LLC-PK1 and MCF-7, whereas baicalein and myricetin were able to induce apoptosis in HT-29 and Caco-2 cells. In conclusion, flavonoids of the flavone, flavonol, flavanone, and isoflavone classes possess antiproliferative effects in different cancer cell lines. The capability of flavonoids for growth inhibition and induction of apoptosis can not be predicted on the basis of their chemical composition and structure.

Apoptosis↗
PubMed1992

Inhibition of microsome-mediated binding of benzo[a]pyrene to DNA by flavonoids either in vitro or after dietary administration to rats.

The in vitro and in vivo effects of selected natural flavonoids (flavone, flavanone, tangeretin, quercetin, chrysin) on the microsome-catalysed binding of [3H]benzo[a]pyrene to calf thymus DNA were investigated and compared with those of two synthetic flavonoids, 7,8-benzoflavone and 5,6-benzoflavone. In vitro addition of these flavonoids (0.1 mM) to an incubation system containing hepatic microsomes prepared from Aroclor 1254-pretreated rats strongly inhibited BaP-DNA adduct formation (72-89%). The incubation of BaP with hepatic microsomes prepared from animals fed 0.3% quercetin, tangeretin and 7,8-benzoflavone for 2 weeks also resulted in less effective binding of BaP metabolites to added DNA, than with microsomes from untreated rats. Other tested compounds, chrysin, flavone, flavanone and 5,6-benzoflavone showed no or little effect. The influence of flavonoid pretreatment on hepatic microsomal enzymes involved in BaP metabolism has also been examined. Aryl hydrocarbon hydroxylase activity was moderately increased (1.5-1.8-fold) in microsomes prepared from rats fed flavone, tangeretin, 7,8-benzoflavone and 5,6-benzo-flavone. Epoxide hydrolase activity was enhanced by 7,8-benzoflavone (1,6-fold), and by flavone and flavanone (5-fold). These results confirm that flavonoids, in vitro, are potent inhibitors of carcinogen-DNA binding. Oral administration of 0.3% flavonoids alters the properties of liver microsomes, resulting in the decreased ability of BaP metabolites to bind DNA.

Animals↗
PubMed2005

Impact of high pressure and pulsed electric fields on bioactive compounds and antioxidant activity of orange juice in comparison with traditional thermal processing.

Bioactive compounds (vitamin C, carotenoids, and flavanones) and DPPH* radical scavenging capacity (RSC) were measured in orange juice (OJ) subjected to different technologies. High pressure (HP) (400 MPa/40 degrees C/1 min), pulsed electric fields (PEF) (35 kVcm(-1)/750 micros), low pasteurization (LPT) (70 degrees C/30 s), high pasteurization (HPT) (90 degrees C/1 min), HPT plus freezing (HPT+F) (-38 degrees C/15 min), and freezing (F) were studied. Among the treatments assayed, even though the losses in total vitamin C were < 9%, treatments with the higher temperatures tended to show the higher decrease in the content of both forms of vitamin C. HP treatment led to an increased (P < 0.05) carotenoid release (53.88%) and vitamin A value (38.74%). PEF treatment did not modify individual or total carotenoids content. Traditional thermal treatments did not exert any effect on total carotenoid content or vitamin A value. With regard to individual carotenoid extraction, HPT and HPT+F led to different releases of carotenoids. With respect to flavanones, HP treatment led to increased (P < 0.05) naringenin (20.16%) and hesperetin (39.88%) contents, whereas PEF treatment did not modify flavanone content. In general, pasteurization and freezing process led to a diminished (P < 0.05) naringenin content (16.04%), with no modification in hesperetin. HP and PEF treatments did not modify DPPH* RSC. In the case of traditional thermal technologies, HPT treatment showed a decrease (P < 0.05) in RSC (6.56%), whereas LPT, HPT+F, and F treatments did not modify RSC. Vitamin C modulated RSC, in terms of antioxidant concentration (EC50) and kinetics (AE = 1/EC50TEC50), in the treated and untreated OJ. In summary, HP and PEF technologies were more effective than HPT treatment in preserving bioactive compounds and RSC of freshly squeezed orange juice.

Antioxidants↗
PubMed2005

Bioavailability and antioxidant effects of orange juice components in humans.

Seven healthy females and six males consumed daily 256 mg of vitamin C, 271 mg of flavanones (mainly as glycosides), 6 mg of carotenoids (mainly xanthophylls and cryptoxanthins), and 0.16 mg of folate by incorporation of daily three times 236 mL of not from concentrate orange juice (OJ) into their habitual diet. At the end of 3 weeks, mean vitamin C, folate, carotenoid, and flavanone plasma concentrations increased significantly relative to baseline by 59% (p < 0.001), 46% (p = 0.018), and 22% (p < 0.001), and 8-fold (p = 0.045), respectively. Flavanones were excreted in urine 9-fold more at the end of the intervention (p = 0.01) but returned to baseline 2 days after study completion. After the 3 week intervention, plasma concentrations of vitamins A and E did not change. 8-Hydroxydeoxyguanosine in white blood cells declined by 16% (p = 0.38; n = 11), and in individuals with high baseline concentrations by 29% (p = 0.36; n = 7), respectively. Low-density lipoprotein (LDL)-/high-density lipoprotein (HDL)-cholesterol ratios decreased but cholesterol (HDL, LDL, total) and thiobarbituric acid reactive substance plasma concentrations did not change significantly. We conclude from this pilot study that OJ is an excellent food source to enhance circulating concentrations of valuable hydrophilic as well as lipophilic phytochemicals.

Antioxidants↗
PubMed2002

Plasma concentrations of the flavonoids hesperetin, naringenin and quercetin in human subjects following their habitual diets, and diets high or low in fruit and vegetables.

OBJECTIVES: To determine the fasting plasma concentrations of quercetin, hesperetin and naringenin in human subjects consuming their habitual diets, and diets either high or low in fruit and vegetables. To investigate whether plasma concentrations of flavanones can serve as biomarkers of their intake. DESIGN: This was a cross-over, strictly controlled dietary intervention consisting of a 2 week baseline period, and two 5 week dietary periods with a 3 week wash-out period in between. The low-vegetable diet contained few fruit and vegetables and no citrus fruit. The high-vegetable diet provided various fruits and vegetables daily including on average one glass of orange juice, one-half orange and one-half mandarin. SUBJECTS: Thirty-seven healthy females. RESULTS: The high-vegetable diet provided 132 mg of hesperetin and 29 mg of naringenin. The low-vegetable diet contained no flavanones. The mean plasma hesperetin concentration increased from 12.2 nmol/l after the low-vegetable diet to 325 nmol/l after the high-vegetable diet. The respective increase for naringenin was from <73.5 nmol/l for all subjects to a mean value of 112.9 nmol/l. The mean plasma quercetin concentration was 52 nmol/l after the baseline period, during which habitual diets were consumed, and it did not change significantly during the intervention. Interindividual variation in the plasma levels of hesperetin and naringenin was marked and, after the baseline and wash-out periods, and the low-vegetable diet, a majority of the samples had plasma flavanone levels below the limit of detection. After the high-vegetable diet, hesperetin and naringenin were detectable in 54 and 22% of all samples. Quercetin was detectable in nearly all samples after all study periods. CONCLUSION: Hesperetin, naringenin and quercetin are bioavailable from the diet, but the plasma concentrations of hesperetin and naringenin are poor biomarkers of intake.

Adult↗
PubMed2003

The compositional characterisation and antioxidant activity of fresh juices from sicilian sweet orange (Citrus sinensis L. Osbeck) varieties.

Epidemiological evidence has suggested that consumption of fruit and vegetables reduces the risk of both cancer and cardiovascular diseases, potentially through the biological actions of components such as vitamin C, vitamin E, flavonoids and carotenoids. Citrus species are extremely rich sources in vitamin C and flavanones, a class of compounds which belongs to the flavonoids family. A comparison of the phenolic compositions, the ascorbic acid contents and the antioxidant activities of fresh Sicilian orange juices from pigmented (Moro, Tarocco and Sanguinello) and non-pigmented (Ovale, Valencia and Navel) varieties of orange (Citrus sinensis L. Osbeck), was undertaken. The simultaneous characterisation and quantification of the major flavanone, anthocyanin and hydroxycinnamate components were attained by HPLC with diode array detection. Differences between varieties in terms of the flavanone glycoside content, particularly hesperidin, were observed, with the Tarocco juices reporting the highest content. Furthermore, cyanidin-3-glucoside and cyanidin-3-(6"-malonyl)-glucoside were predominant in all the pigmented varieties, but their concentration was higher in the juices of the Moro variety. Quantitatively, the major antioxidant component of all juices was ascorbic acid and its concentration was significantly correlated (r = 0.74, P < 0.001) with the total antioxidant activity of the juices, determined in vitro using the ABTS radical cation decolorization assay. Similarly, hydroxycinnamates (r = 0.73, P < 0.01) and anthocyanins (r = 0.98, P < 0.001) content showed a good correlation with the determined antioxidant capacity. Therefore orange juices, particularly those rich in anthocyanins, may represent a significant dietary source of flavonoids.

Antioxidants↗
PubMed2004

Induction and inhibition of aromatase (CYP19) activity by natural and synthetic flavonoid compounds in H295R human adrenocortical carcinoma cells.

Flavonoids and related structures (e.g., flavones, isoflavones, flavanones, catechins) exert various biological effects, including anticarcinogenic, antioxidant and (anti-)estrogenic effects, and modulation of sex hormone homeostasis. A key enzyme in the synthesis of estrogens from androgens is aromatase (cytochrome P450 19; CYP19). We investigated the effects of various natural and synthetic flavonoids on the catalytic activity and promoter-specific expression of aromatase in H295R human adrenocortical carcinoma cells. Natural flavones were consistently more potent inhibitors than flavanones. IC(50) values for 7-hydroxyflavone, chrysin, and apigenin were 4, 7, and 20 microM, respectively; for the flavanones 7-hydroxyflavanone and naringenin the IC(50) values were 65 and 85 microM, respectively. The steroidal aromatase inhibitor (positive control) 4-hydroxyandrostenedione had an IC(50) of 20 nM. The inhibition by apigenin and naringenin coincided with some degree of cytotoxicity at 100 microM. The natural flavonoid derivative rotenone (IC(50) 0.3 microM) was the most potent aromatase inhibitor tested. Several synthetic flavonoid and structurally related quinolin-4-one analogs inhibited aromatase activity. The most potent inhibitor was 4'-tert-butyl-quinolin-4-one (IC(50) 2 microM), followed by two 2-pyridinyl-substituted alpha-naphthoflavones (IC(50)s 5 and >30 microM). The two 2-pyridinyl-substituted gamma-naphthoflavones consistently produced biphasic concentration-response curves, causing about 1.5-fold aromatase induction at concentrations below 1 microM and inhibition above that level (IC(50)s 7 and >30 microM). The natural flavone quercetin and isoflavone genistein induced aromatase activity 4- and 2.5-fold induction, respectively, at 10 microM. This coincided with increased intracellular cAMP concentrations and increased levels of the cAMP-dependent pII and to a lesser extent 1.3 promoter-specific aromatase transcripts. These results shed light on the structure-activity relationships for aromatase inhibition as well as mechanisms of induction in human H295R cells.

Adrenal Gland Neoplasms↗
PubMed2005

Preparative monohydroxyflavanone syntheses and a protocol for gas chromatography-mass spectrometry analysis of monohydroxyflavanones.

We describe a facile efficient, and preparative approach for monohydroxyflavanone syntheses. Using this protocol, a hydroxyl is regio-selectively introduced at one carbon of a flavanone A- or B-ring per synthesis. The seven possible isomers were each synthesized from the corresponding monomethoxymethoxylated 2'-hydroxychalcones in acidic solution. These monohydroxyflavanones were characterized using a gas chromatography-mass spectrometry (GC-MS) system that incorporated a DB-5 capillary column. Ours is the first report of a preparative synthetic method during which a single hydroxyl can be selectively added to a flavanone A- or B-ring at any position. We are also the first to develop a procedure that separates the seven isomers by GC and characterizes the mass spectra of the isomers. Both the synthetic method and the GC-MS conditions may become important tools during future flavanone metabolism and oxidation studies.

Flavanones↗
PubMed1995

Effects of flavonoids on parietal cell acid secretion, gastric mucosal prostaglandin production and Helicobacter pylori growth.

The effect of the flavonoids flavone, flavanone and quercetin on parietal cell acid production, H+/K(+)-ATPase activity, gastric mucosal prostaglandin E2 biosynthesis and Helicobacter pylori growth was studied. All flavonoids inhibited acid production in isolated parietal cells in response to histamine and dibutyryl-cAMP stimulation (IC50 values between 26 and 139 mumol/l) and inhibited H+/K(+)-ATPase activity. Inhibition of H+/K(+)-ATPase activity was dependent on the ATP concentration. Fluorescence measurements showed that flavanone reacts with ATP. These findings indicate that the inhibitory action of flavonoids on H+/K(+)-ATPase activity is related to their ability to complex ATP. Flavone and flavanone (10 and 100 mumol/l) stimulated prostaglandin E2 production in isolated gastric mucosal cells. Furthermore, the compounds inhibited Helicobacter pylori growth in a concentration-dependent manner. From these finding it appears that flavonoids are a group of compounds which could have a therapeutic potential for treatment of gastrointestinal diseases associated with Helicobacter pylori infection.

Adenosine Triphosphate↗
PubMed2004

Phytochemistry and preliminary biological evaluation of Cyathostemma argenteum, a malaysian plant used traditionally for the treatment of breast cancer.

Bioassay guided fractionation of the roots of Cyathostemma argenteum using the brine shrimp resulted in the isolation of two uncommon flavanones, 2,5-dihydroxy-7-methoxy flavanone 1 and 2,5-dihydroxy-6,7-dimethoxy flavanone 2 while the stem bark yielded the related compounds 5-hydroxy-7-methoxy flavone 3 and 5-hydroxy-6,7-dimethoxy flavone 4. The alkaloids liriodenine 5 and discretamine 6 as well as benzyl benzoate 7 were isolated from the roots and 6 was also isolated from the stembark. In cytotoxicity tests using four human breast cancer cell lines, 1 and 2 were weakly toxic to MCF-7 cells (IC(50) = 19.6 and 19.0 microM, respectively) but showed little activity against MCF-7 cells resistant to doxorubicin or against two oestrogen receptor-deficient cell lines. Compound 5, but not 6 and 7, was moderately cytotoxic against all four cell lines. These results are discussed in the context of the traditional use of C. argenteum in the treatment of breast cancer.

Animals↗
PubMed2005

Multiple mutagenesis of P450 isoflavonoid synthase reveals a key active-site residue.

The leguminous isoflavonoid skeleton is constructed by P450 2-hydroxyisoflavanone synthase (CYP93C). Two active-site residues of CYP93C2, Ser 310 and Lys 375, are critical for unusual aryl migration of the flavanone substrate. Leu 371 is located near the substrate in a homology model, and mutant proteins regarding this residue were expressed in recombinant yeast microsomes. The single mutant, L371V, yielded only inactive P420, but multiple mutants incorporating K375T restored the P450 fold: the S310T-L371V-K375T triple mutant showed four times higher P450 level than the wild type. L371V-K375T and S310T-L371V-K375T produced a mixture of major 3beta-hydroxyflavanone and minor flavone, and 100% flavone, respectively, from a flavanone. Thus, Leu 371 appeared to control the substrate accommodation in favor of hydrogen abstraction from C-3 of the flavanone molecule and contribute to the P450 fold under the presence of Lys 375, the residue responsible for aryl migration. The molecular evolution of CYP93 enzymes is discussed.

Binding Sites↗
PubMed2005

Preparative isolation and separation of a novel and two known flavonoids from Patrinia villosa Juss by high-speed counter-current chromatography.

Preparative high-speed counter-current chromatography (HSCCC) was successfully used for isolation and separation three flavonoids including bolusanthol B, a novel compound named 5,7,2',6'-tetrahydroxy-6,8-di(gamma,gamma-dimethylallyl) flavanone and tetrapterol I from Patrinia villosa Juss using two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water at the volume ratio of 10:11:11:8 (v/v). A total of 25.4 mg bolusanthol B, 52.5 mg 5,7,2',6'-tetrahydroxy-6,8-di(gamma,gamma-dimethylallyl) flavanone and 50.2 mg tetrapterol I were obtained from 250 mg crude extract with purities of 96.8%, 99.2% and 99.3%, respectively determined by HPLC in one single operation and less than 5 h. The structure identification was performed by UV, IR, MS, 1H NMR, 13C NMR and 2D NMR. Among then, bolusanthol B and tetrapterol I were obtained from the plant of Patrinia genius for the first time, and 5,7,2',6'-tetrahydroxy-6,8-di(gamma,gamma-dimethylallyl) flavanone was a novel prenylated flavonoid and discovered from nature for the first time.

Countercurrent Distribution↗
PubMed2000

Spectrophotometric and coulometric detection in the high-performance liquid chromatography of flavonoids and optimization of sample treatment for the determination of quercetin in orange juice.

The capabilities of spectrophotometric and electrochemical detection techniques were investigated for the high-performance liquid chromatographic determination of flavonoids. Liquid chromatographic analyses were performed on eleven compounds belonging to three different classes of flavonoids: flavanone glycosides, flavone and flavonol aglycones. Separation of all compounds examined was carried out under reversed-phase conditions on a C18 narrow-bore column for UV detection, whereas for electrochemical detection, a C18 standard-bore column was used. UV analyses were carried out at 280 nm for flavanones and at 265 nm for flavones and flavonols, whereas controlled-potential coulometric measurements were performed using a porous graphite electrode. Analytical performances of the methods were compared in terms of linearity, limits of detection (LODs) and precision. Linearity over two orders of magnitude and LODs at low-ppm levels (0.06-1 mg/l) were demonstrated for all techniques considered. Instrumental precision in terms of relative standard deviation was found to be between 0 and 5% for the liquid chromatography (LC)-UV system and between 0.6 and 10% for the LC-electrochemical detection (ED) system. The methods developed were applied to the analysis of flavanones and flavonols in a real sample, such as an extract of orange juice. Even though quercetin glycoside is mostly present in orange juice as rutin, other different glycosides of this flavonol could be present; on this basis, the hydrolysis of all glycosides to aglycone allows one to obtain more accurate data on the flavonol concentration in orange juice. To avoid sample degradation and to increase extraction efficiency, quercetin hydrolysis was optimized using a central composite design to investigate the effects of acid concentration and hydrolysis time on extraction recovery.

Beverages↗
PubMed1997

The inhibition by flavonoids of 2-amino-3-methylimidazo[4,5-f]quinoline metabolic activation to a mutagen: a structure-activity relationship study.

The mutagenicity of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) in Salmonella typhimurium TA98 is inhibited by flavonoids with distinct structure-antimutagenicity relationships (Edenharder, R., I. von Petersdorff I. and R. Rauscher (1993). Antimutagenic effects of flavonoids, chalcones and structurally related compounds on the activity of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and other heterocyclic amine mutagens from cooked food, Mutation Res., 287, 261-274). With respect to the mechanism(s) of antimutagenicity, the following results were obtained here. (1) 7-Methoxy- and 7-ethoxyresorufin-O-dealkylase activities in rat liver microsomes, linked to cytochrome P-450-dependent 1A1 and 1A2 monooxygenases catalyzing oxidation of IQ to N-hydroxy-IQ (N-OH-IQ), were effectively inhibited by 16 flavonoids (IC50: 0.4-9.8 microM). Flavones and flavonols are in general more potent enzyme inhibitors than flavanones, isoflavones, and chalcones. Among flavones the presence of hydroxyl or methoxyl groups resulted in minor changes only. However, among flavonols and flavanones the parent compounds exerted the strongest inhibitory effects, which decreased in dependence on number and position of hydroxyl functions. Contrary to the results obtained in the Salmonella assay in the tests with alkoxyresorufins no extraordinary counteracting effects of isoflavones, of hydroxyl groups at carbons 6 or 2' or of the elimination of ring B (benzylideneacetone) were detected. (2) No effects of flavonoids on NADPH-dependent cytochrome P-450 reductase activity could be detected. (3) The effects of 30 flavonoids on mutagenicity induced by N-OH-IQ in S. typhimurium TA98NR were again structure dependent. The most striking feature was the, in principle, reverse structure-antimutagenicity pattern as compared to IQ: non-polar compounds were inactive and a 50% inhibition was achieved only by some flavones and flavonols (IC50: 15.0-148 nmol/ml top agar). Within the flavone and flavonol subgroups inhibitory effects increased in dependence on number and position of hydroxyl functions. Isoflavones and flavanones, however, as well as glycosides, were inactive. Hydroxyl groups at carbons 7, 3', 4', and 5' generated antimutagenic compounds, a hydroxyl function at C5 was ineffective, but hydroxyls at C3 and 6 as well as methoxyl groups at C3' (isorhamnetin) or 4' (diosmetin) generated comutagenic compounds. 4. Cytosolic activation of IQ to mutagenic metabolites as determined by experiments with the hepatic S105 fraction comprises about 10% of the mutagenicity after activation by the combined microsomal and cytosolic fractions (S9). The pattern of inhibition as produced by 20 flavonoids was closely similar to that observed with the S9 fraction. 5. In various experiments designed for modulation of the mutagenic response, it could be shown that further mechanisms of flavonoid interaction with the overall mutagenic process may exist, such as interactions with biological membranes (luteolin, fisetin) and effects on fixation and expression of.DNA damage (flavone, fisetin).

Animals↗
PubMed1997

Effects of co-administration of butylated hydroxytoluene, butylated hydroxyanisole and flavonoids on the activation of mutagens and drug-metabolizing enzymes in mice.

Effects of co-administration of food additives and naturally occurring food components were studied on the activation of mutagens. Male mice (ddY) were given diets containing butylated hydroxytoluene (BHT) or butylated hydroxyanisole (BHA) and flavone or flavanone (2,3-dihydroflavone) for two weeks and the ability of hepatic microsomes to activate aflatoxin B1, benzo[a]pyrene and N-nitrosodimethylamine was determined by the mutagenicity test. Co-administration of an antioxidant (0.1% BHT or 0.2% BHA in diet) and a flavonoid (0.1% flavone or 0.1% flavanone) resulted in additive effects on the activation of aflatoxin B1 and benzo[a]pyrene, while the activation of N-nitrosodimethylamine was not elevated significantly by the co-administration. To understand the mechanism for the additive effects, induction of specific isozymes of cytochrome P450 involved in the activation of the mutagens was studied. Co-administration of BHT (0.1%) and flavone (0.1%) increased markedly the levels of proteins and the activities of the enzymes related to the isozymes of CYP2A and CYP2B, while co-administration of BHA (0.2%) and flavanone (0.1%) elevated those related to CYP1A. Further, the activation of aflatoxin B1 and benzo[a]pyrene in hepatic microsomes was inhibited by the antibodies against these isozymes, which suggested that the enhanced activation of the mutagens by the co-administration might be mediated by the induction of these isozymes.

Animals↗
PubMed2004

Fractionation of orange peel phenols in ultrafiltered molasses and mass balance studies of their antioxidant levels.

Orange peel molasses, a byproduct of juice production, contains high concentrations of phenols, including numerous flavanone and flavone glycosides, polymethoxylated flavones, hydroxycinnamates, and other miscellaneous phenolic glycosides and amines. Extensive fractionation of these phenols was achieved by adsorption, ion exchange, and size exclusion chromatography. Size exclusion chromatography effectively separated the different classes of flavonoids in ultrafiltered molasses, including the polymethoxylated flavones, flavanone-O-trisaccharides, flavanone- and flavone-O-disaccharides, and, finally, flavone-C-glycosides. Mass spectral analysis of the early-eluting flavonoid fractions off the size exclusion column revealed a broad collection of minor-occurring flavone glycosides, which included, in part, glycosides of limocitrin, limocitrol, and chrysoeriol. Most hydroxycinnamates in the molasses were recovered by ion exchange chromatography, which also facilitated the recovery of fractions containing many other miscellaneous phenols. Total antioxidant levels and total phenolic contents were measured for the separate categories of phenols in the molasses. Inhibition of the superoxide anion reduction of nitroblue tetrazolium showed that a significant amount of the total antioxidant activity in orange peel molasses was attributable to minor-occurring flavones. The miscellaneous phenolic-containing fractions, in which a large portion of the total phenolic content in molasses occurred, also constituted a major portion of the total antioxidants in ultrafiltered molasses.

Antioxidants↗
PubMed2006

New bitter-masking compounds: hydroxylated benzoic acid amides of aromatic amines as structural analogues of homoeriodictyol.

Starting from the known bitter-masking flavanones eriodictyol and homoeriodictyol from herba santa some structurally related hydroxybenzoic acid amides of benzylamines were synthesized and evaluated as masking agents toward bitterness of caffeine by sensory methods. The closest structural relatives of homoeriodictyol, the hydroxybenzoic acid vanillylamides 5-9, were the most active and were able to reduce the bitterness of a 500 mg L(-1) caffeine solution by about 30% at a concentration of 100 mg L(-1). 2,4-Dihydroxybenzoic acid vanillylamide 7 showed a clear dose-dependent activity as inhibitor of the bitter taste of caffein between 5 and 500 mg L(-1). Additionally, it was possible to reduce the bitterness of quinine and salicine but not of the bitter peptide N-l-leucyl-l-tryptophan. Combinations of homoeriodictyol and amide 7 showed no synergistic or antagonistic changes in activity. The results for model compound 7 suggested that the hitherto unknown masking mechanism is probably the same for flavanones and the new amides. In the future, the new amides may be alternatives for the expensive flavanones to create flavor solutions to mask bitterness of pharmaceuticals or foodstuffs.

Amides↗
PubMed2001

Cytotoxic flavonoids with isoprenoid groups from Morus mongolica.

A new pyranoflavanone, sanggenol L (1), a Diels-Alder type adduct regarded as a cycloaddition product of a dehydrogeranylflavanone and a prenylchalcone, sanggenol M (2), along with four new 2-arylbenzofurans with isoprenoid units, mulberrofurans W-Z (3-6), were isolated together with 10 known flavonoids from Chinese Morus mongolica. The structures of these novel compounds were elucidated by spectroscopic methods. All flavanones investigated here showed higher cytotoxicity against human oral tumor cell lines (HSC-2 and HSG) than against normal human gingival fibroblasts (HGF). Among them, the cytotoxicity of compound 2 and the Diels-Alder type flavanone sanggenon C (7) isolated from Morus cathayana were the most potent. On the other hand, seven 2-arylbenzofurans exhibited lower cytotoxicity and tumor specificity as compared with flavanones.

Antineoplastic Agents↗