Cytotoxic effects of the dietary flavones chrysin and apigenin in a normal trout liver cell line

Many flavonoids have been shown to possess prooxidant properties, capable of causing oxidative stress, especially at larger doses. Here, we examined the potential cell toxicity caused by exposure to the hydroxylated flavones chrysin, apigenin, luteolin and quercetin in comparison to the methylated flavones 5,7-dimethoxyflavone and 3',4'-dimethoxyflavone in normal Rainbow trout hepatocytes. The hydroxylated flavones, especially chrysin, demonstrated cell toxicity and inhibition of DNA synthesis at very low (2 microM) concentrations. The cytotoxicity of chrysin may partially be due to its metabolism by myeloperoxidase, which was shown to be present in these normal trout liver cells (164pmol/(min mg protein)). In contrast, methylated flavones showed no significant metabolism by myeloperoxidase and no signs of toxicity, even at much higher concentrations. These results may be useful for further investigations of cytotoxicity of dietary flavonoids.     

Accumulation and metabolism of the anticancer flavonoid 5,7-dimethoxyflavone compared to its unmethylated analog chrysin in the Atlantic killifish

The use of dietary flavonoids as potential chemopreventive agents is a concept of increasing interest. Recent findings indicate that methylated flavones have the advantage of increased metabolic stability. One such compound, the naturally-occurring 5,7-dimethoxyflavone (5,7-DMF), has been shown to be a potential chemopreventive agent in human cancer originating from the liver, mouth, esophagus and lung. As bioavailability is a key issue for potential in vivo effects, the tissue accumulation and biliary elimination of 5,7-DMF and its non-methylated analog chrysin were examined in a small fish model (Fundulus heteroclitus). The fish were exposed to 5,7-DMF, chrysin or vehicle control (DMSO<0.01%) in seawater for 8h. Toxicity was not observed at the 5microM exposure level. Tissues and bile were harvested and analyzed by HPLC and LC/MS for quantitation and identification of parent compound and metabolites. 5,7-DMF accumulated 20-fold to 100-fold in all tissues examined, with the highest accumulation in liver and brain, whereas chrysin was barely detectable in any tissues except the liver. The bile of chrysin-exposed fish contained very low concentrations of unchanged chrysin but high concentrations of two glucuronic acid conjugates. In the bile of 5,7-DMF-exposed fish, the parent compound was detectable in significant amounts along with glucuronic acid conjugates of O-demethylated 5,7-DMF. In conclusion, our study demonstrated high tissue accumulation and limited metabolism of 5,7-DMF compared to chrysin in vivo, making this flavone a promising chemopreventive molecule.     

Flavonoids in the black rhizomes of Boesenbergia panduta

5-Hydroxy-7-methoxyflavanone, 5,7-dimethoxyflavanone, 5-hydroxy-7-methoxyflavone 5-hydroxy-7,4′-dimethoxyflavone, 5,7-dimethoxyfiavone, 5,7,4′-trimethoxyflavone, 5,7,3′,4′-tetramethoxyflavone, 5-hydroxy-3,7-dimethoxyflavone, 5-hydroxy-3,7,4′-trimethoxyflavone, 3,5,7-trimethoxyflavone and 5-hydroxy-3,7,3′,4′-tetramethoxyflavone have been isolated from the black rhizomes of Boesenbergia pandurata.     

Phytoestrogens as inhibitors of fungal 17beta-hydroxysteroid dehydrogenase

Different phytoestrogens were tested as inhibitors of 17beta-hydroxysteroid dehydrogenase from the fungus Cochliobolus lunatus (17beta-HSDcl), a member of the short-chain dehydrogenase/reductase superfamily. Phytoestrogens inhibited the oxidation of 100 microM 17beta-hydroxyestra-4-en-3-one and the reduction of 100 microM estra-4-en-3,17-dione, the best substrate pair known. The best inhibitors of oxidation, with IC(50) below 1 microM, were flavones hydroxylated at positions 3, 5 and 7: 3-hydroxyflavone, 3,7-dihydroxyflavone, 5,7-dihydroxyflavone (chrysin) and 5-hydroxyflavone, together with 5-methoxyflavone. The best inhibitors of reduction were less potent; 3-hydroxyflavone, 5-methoxyflavone, coumestrol, 3,5,7,4'-tetrahydroxyflavone (kaempferol) and 5-hydroxyflavone all had IC(50) values between 1 and 5 microM. Docking the representative inhibitors chrysin and kaempferol into the active site of 17beta-HSDcl revealed the possible binding mode, in which they are sandwiched between the nicotinamide moiety and Tyr212. The structural features of phytoestrogens, inhibitors of both oxidation and reduction catalyzed by the fungal 17beta-HSD, are similar to the reported structural features of phytoestrogen inhibitors of human 17beta-HSD types 1 and 2.     

Phytoestrogens as inhibitors of fungal 17beta-hydroxysteroid dehydrogenase

Different phytoestrogens were tested as inhibitors of 17beta-hydroxysteroid dehydrogenase from the fungus Cochliobolus lunatus (17beta-HSDcl), a member of the short-chain dehydrogenase/reductase superfamily. Phytoestrogens inhibited the oxidation of 100microM 17beta-hydroxyestra-4-en-3-one and the reduction of 100microM estra-4-en-3,17-dione, the best substrate pair known. The best inhibitors of oxidation, with IC(50) below 1microM, were flavones hydroxylated at positions 3, 5 and 7: 3-hydroxyflavone, 3,7-dihydroxyflavone, 5,7-dihydroxyflavone (chrysin) and 5-hydroxyflavone, together with 5-methoxyflavone. The best inhibitors of reduction were less potent; 3-hydroxyflavone, 5-methoxyflavone, coumestrol, 3,5,7,4'-tetrahydroxyflavone (kaempferol) and 5-hydroxyflavone, all had IC(50) values between 1 and 5microM. Docking the representative inhibitors chrysin and kaempferol into the active site of 17beta-HSDcl revealed the possible binding mode, in which they are sandwiched between the nicotinamide moiety and Tyr212. The structural features of phytoestrogens, inhibitors of both oxidation and reduction catalyzed by the fungal 17beta-HSD, are similar to the reported structural features of phytoestrogen inhibitors of human 17beta-HSD types 1 and 2.     

5-Methyl ether flavone glucosides from the leaves of Bruguiera gymnorrhiza

Two new 5-methyl ether flavone glucosides (7,4′,5′-trihydroxy-5,3′-dimethoxyflavone 7-O-β-D-glucopyranoside and 7,4′-dihydroxy-5-methoxyflavone 7-O-β-D-glucopyranoside) were isolated from the leaves of Thai mangrove Bruguiera gymnorrhiza together with 7,3′,4′,5′-tetrahydroxy-5-methoxyflavone, 7,4′,5′-trihydroxy-5,3′-dimethoxyflavone, luteolin 5-methyl ether 7-O-β-D-glucopyranoside, 7,4′-dihydroxy-5,3′-dimethoxyflavone 7-O-β-D-glucopyranoside, quercetin 3-O-β-D-glucopyranoside, rutin, kaempferol 3-O-rutinoside, myricetin 3-O-rutinoside and an aryl-tetralin lignan rhamnoside. The structure of a lignan rhamnoside was found to be related to racemiside, an isolated compound from Cotoneaster racemiflora, and also discussed. Structure determinations were based on analyses of physical and spectroscopic data including 1D- and 2D-NMR.     

Relationship between the methylation status of dietary flavonoids and their growth-inhibitory and apoptosis-inducing activities in human cancer cells

Flavonoids are polyphenolic compounds widely distributed in the plant kingdom. Compelling research indicates that flavonoids have important roles in cancer chemoprevention and chemotherapy possibly due to biological activities that include action through anti-inflammation, free radical scavenging, modulation of survival/proliferation pathways, and inhibition of the ubiquitin-proteasome pathway. Plant polyphenols including the green tea polyphenol (-)-epigallocatechin gallate or (-)-EGCG, and the flavonoids apigenin, luteolin, quercetin, and chrysin have been shown to inhibit proteasome activity and induce apoptosis in human leukemia cells. However, biotransformation reactions to the reactive hydroxyl groups on polyphenols could reduce their biological activities. Although methylated polyphenols have been suggested to be metabolically more stable than unmethylated polyphenols, the practical use of methylated polyphenols as cancer preventative agents warrants further investigation. In the current study, methylated and unmethylated flavonoids were studied for their proteasome-inhibitory and apoptosis-inducing abilities in human leukemia HL60 cells. Methylated flavonoids displayed sustained bioavailability and inhibited cellular proliferation by arresting cells in the G(1) phase. However, they did not act as proteasome inhibitors in either an in vitro system or an in silico model and only weakly induced apoptosis. In contrast, unmethylated flavonoids exhibited inhibition of the proteasomal activity in intact HL60 cells, accumulating proteasome target proteins and inducing caspase activation and poly(ADP-ribose) polymerase cleavage. We conclude that methylated flavonoids lack potent cytotoxicity against human leukemia cells and most likely have limited ability as chemopreventive agents.     

Thymol derivatives from Calea nelsonii

Calea nelsonii yielded, besides the two known thymol derivatives 8,9-epoxy-7-isobutyryloxythymol isobutyrate and 10-acetoxy-8,9-epoxythymol isobutyrate, the five new thymol derivatives 10-acetoxy-8,9-epoxy-7- isobutyryloxythymol isobutyrate, 10-acetoxy-8,9-epoxy-7-hydroxythymol isobutyrate, 8-hydroxy-9-acetoxy-10-isobutyryloxythymol 7-acetoxy-8-hydroxy-9,10-diisobutyryloxythymol and 7-isobutyryloxy-8,9-dihydroxythymol, while C. zacatechichi provided the known flavones 5-hydroxy-7,4′-dimethoxy flavone and 5,7-dihydroxy-4′-methoxyflavone and a known epoxysesquiterpene lactone. The structures of the new compounds were established by spectral methods. Some chemotaxonomic aspects are discussed.     

Flavonoids from the leaf resin of Adenostoma sparsifolium

Four flavonoids were identified from the external leaf extract of Adenostoma sparsifolium: the two new flavones 3, 7-dihydroxy-5, 6-dimethoxyflavone and 3, 5, 7-trihydroxy-8-methoxyflavone and the known compounds galangin and pinocembrin.     

5,6,7-Trisubstituted flavones from Gomphrena martiana

Two 5,6,7-trisubstituted flavones have been isolated from Gomphrena martiana and identified as 5,6-dimethoxy-7-hydroxyflavone and 5,7-dihydroxy-6-methoxyflavone.     

艾纳香化学成分的研究

从艾纳香(Blumea balsamifera DC.)中分离得到12个化合物,通过理化性质和波谱数据分析分别鉴定为;商路素(1),花椒油素(2),2,4-二羟基-6-甲氧基苯乙酮(3),5,7-二羟基色原酮(4),金丝桃苷(5),异槲皮苷(6),3′,4′,5,7-四羟基-3-甲氧基黄酮(7),槲皮素(8),槲皮素-3′-甲氧基-3-O-β-D-半乳吡喃糖苷(9),4′,5,7-三羟基-3,3′-二甲氧基黄酮(10),3,5,7-三羟基-3′,4′-二甲氧基黄酮(11),木犀草素(12).其中,化合物3-7和9- 11为首次从该属植物中分离得到.     

Flavonoids from Artemisia ludoviciana var. ludoviciana

Nineteen flavonoids were isolated from Artemisia ludoviciana var. ludoviciana, including a new 2′- hydroxy- 6-methoxyflavone, 5,7,2′,4′-tetrahydroxy-6,5′-dimethoxyflavone. The known compounds include quercetagetin 3,6,3′,4′-tetramethyl ether, eupatilin, 5,7-dihydroxy-3,6,8,4′-tetramethoxyflavone, luteolin 3′,4′-dimethyl ether, jaceosidin, 5,7,4′-trihydroxy-3,6-dimethoxyflavone, tricin, hispidulin, chrysoeriol, kaempferol 3-methyl ether, apigenin, axillarin, eupafolin, selagin and luteolin together with three flavones which were previously isolated for the first time from Artemisia frigida: 5,7,4′-trihydroxy-6, 3′,5′-trimethoxyflavone, 5,7,3′-trihydroxy-6,4′,5′-trimethoxyflavone and 5,7,3′,4′-tetrahydroxy-6,5′- dimethoxyflavone.     

No evidence for the in vivo activity of aromatase-inhibiting flavonoids

Measurements of the aromatase-inhibiting and antioxidative capacities of flavonoids in vitro showed that slight changes in flavonoid structure may result in marked changes in biological activity. Several flavonoids such as 7-hydroxyflavone and chrysin (5,7-dihydroxyflavone) were shown to inhibit the formation of 3H-17beta-estradiol from 3H-androstenedione (IC(50)<1.0 microM) in human choriocarcinoma JEG-3 cells and in human embryonic kidney cells HEK 293 transfected with human aromatase gene (Arom+HEK 293). Flavone and quercetin (3,3',4',5,7-pentahydroxyflavone) showed no inhibition (IC(50)>100 microM). None of the requirements for optimal antioxidative capacity (2,3-double bond with 4'-hydroxy group, 3-hydroxyl group, 5,7-dihydroxy structure and the orthodihydroxy structure in the B-ring) is relevant for the maximum inhibition of aromatase by flavonoids. After oral administration to immature rats at a dose of 50 mg/kg body weight, which considerably exceeds amounts found in daily human diets, neither aromatase-inhibiting nonestrogenic flavonoids, such as chrysin, nor estrogenic flavonoids, such as naringenin and apigenin, induced uterine growth or reduced estrogen- or androgen-induced uterine growth. The inability of flavonoids to inhibit aromatase and, consequently, uterine growth in short-term tests may be due to their relatively poor absorption and/or bioavailability.     

白木香树干中的黄酮类成分

从白木香[Aquilaria smensis(Lour.)Gilg]树干的乙醇提取物中分离得到5个黄酮类化合物,经波谱分析,分别鉴定为:洋芹素-7,4'-二甲醚(1)、5-羟基-7,3',4'-三甲氧基黄酮(2)、木犀草素-7,4'-二甲醚p)、芫花素(4)和4',5-二羟基-3',7-二甲氧基黄酮(5).以上化合物均为首次从该种植物树干中分离得到.     

Biochemical and pharmacological development of steroidal inhibitors of aromatase

Androstenedione analogs containing 7 alpha-substituents have proven to be potent inhibitors of aromatase both in vitro and in vivo. Several of these agents have exhibited higher affinity for the enzyme complex than the substrate. In order to examine further the interaction(s) of 7-substituted steroids with aromatase, biochemical and pharmacological studies were performed on 7 alpha-thiosubstituted androstenediones and 7-substituted 4,6-androstadiene-3,17-diones. Potent inhibition of aromatase activity in human placental microsomes has been observed with several new 7 alpha-thiosubstituted androstenediones. 7-Benzyl- and 7-phenethyl-4,6-androstadiene-3,17-diones effectively inhibited microsomal aromatase, with apparent Kis ranging from 61 to 174 nM. On the other hand, 7-phenyl-4,6-androstadiene-3,17-dione exhibited poor activity, with an apparent Ki of 1.42 microM. Similar inhibitory activity was observed with reconstituted, purified cytochrome P450Arom preparations. Additionally, these agents were evaluated for inhibition of aromatase activity in two human carcinoma cell lines, the MCF-7 human mammary cancer line and the JAr choriocarcinoma line. The 7 alpha-thiosubstituted androstenediones and 7-substituted 4,6-androstadiene-3,17-diones produced dose-dependent inhibitions of aromatase activity in the cell cultures. The most effective inhibitors were the 7 alpha-substituted androstenediones, with EC50 values ranging from 7.3 to 105 nM. Finally, the JAr cell culture system exhibited prolonged inhibition of aromatase activity following exposure to 7 alpha-APTADD, suggesting enzyme inactivation by this inhibitor. Thus, these agents are effective aromatase inhibitors, and the results encourage further development of this group of medicinal agents for the treatment of estrogen-dependent mammary carcinoma.     

The Chemical Constituents of Elsholtzia ciliata (Thund.) Hyland

Fourteen compounds have been obtained from the Elsholtzia ciliata (Thund.) Hyland. Their structures were identified by spectral and chemical methods as following: Ⅰ. 6-methyl-tritriacontane, Ⅱ. 13-cyclohexyl-hexoacosane, Ⅲ. β-sitosterol, Ⅳa. palmitic acid, Ⅳb. linoleic acid, Ⅳc. linolenic acid, Ⅴ. ursolic acid, Ⅵ. 5-hydroxy--6, 7-dimethoxyflavone, Ⅶ. 5-hyd-foxy-7, 8-dimethoxyflavone, Ⅷ. 5,7-dihydroxy-4'-methoxyflavone, Ⅸ. 5-hydroxy-7,4'-dime-thoxyflavone, Ⅹ.β-sitosterol-β-D-glucoside, Ⅺ. 5-hydroxy-6-methylflavanone-7-O-α-D-galacopy-ranoside, Ⅻ. acacetin-7-O-β-glucoside. Among all the compounds, Ⅺ is a new compound. Except for Ⅳb and Ⅳc, the other twelve compounds were first found in this plant.     

Aromatase inhibition by flavonoids

Several synthetic flavones were found to inhibit the aromatization of androstenedione to estrone catalyzed by human placental microsomes. Twenty-one compounds were tested and the IC50 of the most active were: flavone, 10 microM; 7-hydroxyflavone, 0.5 microM; 7,4'-dihydroxyflavone, 2.0 microM; flavanone, 8.0 microM; and 4'-hydroxyflavanone, 10 microM. Most of the others had IC50 values ranging from 80 to greater than 200 microM. These findings show that 4'-hydroxylation results in either no change or very little change in IC50 for flavanone, isoflavone and isoflavanone as well as other ring A hydroxylated flavones. Derivatives of flavone with a hydroxyl substituent at position 5, 6 and 7 were also screened. 7-Hydroxyflavone (11) was the most effective competitive inhibitor (IC50 = 0.5 microM) with an apparent Ki value of 0.25 microM. Compound 11 also induced a change in the absorption spectrum of the aromatase cytochrome P-450 which is indicative of substrate displacement. The relative binding affinities of the flavonoid analogs were determined and only ring A adn ring B dihydroxylated analogs were found to bind to the estrogen receptor.     

Iridoid glucosides and flavones from the aerial parts of Avicennia marina

Two new iridoid glucosides, namely, 2'-O-[(2E,4E)-5-phenylpenta-2,4-dienoyl]mussaenosidic acid (1; mussaenosidic acid = [1S-(1alpha,4aalpha,7alpha,7aalpha)]-1-(beta-D-glucopyranosyloxy)-1,4a,5,6,7,7a-hexahydro-7-hydroxy-7-methylcyclopenta[c]pyran-4-carboxylic acid) and 2'-O-(4-methoxycinnamoyl)mussaenosidic acid (2), were isolated from the aerial parts of the mangrove plant Avicennia marina. Beside that, one known iridoid glucoside, 2'-O-coumaroylmussaenosidic acid (3) and four known flavones (flavone = 2-phenyl-4H-1-benzopyran-4-one) including 4',5-dihydroxy-3',7-dimethoxyflavone (4), 4',5-dihydroxy-3',5',7-trimethoxyflavone (5), 4',5,7-trihydroxyflavone (6), and 3',4',5-trihydroxy-7-methoxyflavone (7) were also isolated and identified. The structures of these compounds were elucidated by NMR spectroscopy and by low- and high-resolution mass spectrometry. The chemotaxonomic significance of these findings was discussed. In addition, each isolated compound was evaluated for the ability of alpha,alpha-diphenyl-beta-picrylhydrazyl (DPPH) radical-scavenging activity.     

Aromatase inhibition by 7-substituted steroids in human choriocarcinoma cell culture.

Androstenedione analogs containing 7 alpha-substituents have proven to be potent inhibitors of aromatase both in vitro and in vivo. Several of these agents have exhibited higher affinity for the enzyme complex than the substrate. In order to examine further the interaction(s) of 7-substituted steroids with aromatase, 7-substituted 4,6-androstadiene-3,17-diones were synthesized and demonstrated competitive inhibition of aromatase activity in human placental microsomes. 7-Substituted 1,4,6-androstatriene-3,17-diones demonstrated mechanism-based inhibition of placental aromatase activity. These agents were evaluated for inhibition of aromatase activity in the JAr human choriocarcinoma line. The 7-substituted 4,6-androstadiene-3,17-diones produced dose dependent inhibition of aromatase activity in the cell cultures, with IC50 values ranging from 490 nM to 4.5 microM. However, these agents are less effective when compared to other steroidal inhibitors, such as 7 alpha-thiosubstituted androstenediones. These results on the 7-substituted 4,6-androstadiene-3,17-diones are consistent with the data from biochemical enzyme inhibition studies using human placental aromatase. On the other hand, 7-phenethyl-1,4,6-androstatriene-3,17-dione exhibits greater inhibitory activity, with an IC50 value of 80 nM. Other mechanism-based inhibitors, 7 alpha-(4'-amino)phenylthio-1,4-androstadiene-3,17-dione and 4-hydroxyandrostenedione, also exhibited potent inhibition of aromatase activity in JAr cells. In summary, the most effective B-ring modified steroidal aromatase inhibitors are those derivatives that can project the 7-aryl substituent into the 7 alpha-position.     

Extractive compounds of betulaceae family birch buds (Betula pendula Roth.): IV. Composition of sesquiterpene diols, triols, and flavonoids

This report is devoted to study of the hydrocarbon composition of the extract of buds of birch (family Betulaceae). We identified 3,5-dihydroxy-7,4??-dimethoxyflavone, 5,7-dihydroxy-3,4??-dimethoxyflavone, 7-methoxy-4??,5-dihydroxyflavanone, 4??-methoxy-5,7-hydroxyflavanone, 5??,6??-dihydroxycaryophyllen-4(14),8(15)-diene ((1R,5R,6R,9S)-5,6-dihydroxy-11,11-dimethyl-4,8-methylenebicyclo[7.2.0]-undecane), 5??,6??-dihydroxycaryophyllen-3,8(15)-diene ((1R,5R,6R,9S)-5,6-dihydroxy-11,11-dimethyl-8-methylenebicyclo[7.2.0]undec-3-ene), 6??,9??-dihydroxy-??-humulene((1E,4E,6R,9S)-6,9-dihydroxy-4,11,11-trimethyl-8-methylene-1,4-cycloundecanediene), 5??,6??,8??-trihydroxycariolan, and (1R,5R,6R,8R,9S)-trihydroxycariolan. The gas chromatographic retention indices of all identified compounds were determined.