• Journal of the Korean Chemical Society
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• v.62 no.1
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• pp.19-23
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• 2018

The methylated metabolites of quercetin, rhamnazin and ombuin are highly likely to develop as anticancer and anti-inflammatory agents. In this study, we synthesized rhamnazin through selective methylation of quercetin hydroxyl group, which has not been reported so far. In addition, a new synthetic method was developed to correct the problems of previous synthetic method of ombuin, one of the methylated metabolites of quercetin.

• Journal of Microbiology and Biotechnology
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• v.16 no.4
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• pp.619-622
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• 2006

Biotransformation is a good tool to synthesize regioselective compounds. It could be performed with diverse sources of genes, and microorganisms provide a myriad of gene sources for biotransformation. We were interested in modification of flavonoids, and therefore, we cloned a putative O-methyltransferase from Bacillus cereus, BcOMT-2. It has a 668-bp open reading frame that encodes a 24.6-kDa protein. In order to investigate the modification reaction mediated by BcOMT-2, it was expressed in E. coli as a His-tag fusion protein and purified to homogeneity. Several substrates such as naringenin, luteolin, kaempferol, and quercetin were tested and reaction products were analyzed by thin layer chromatography (TLC) and high performance liquid chromatography (HPLC). BcOMT-2 could transfer a methyl group to substrates that have a 3' functional hydroxyl group, such as luteolin and quercetin. Comparison of the HPLC retention time and UV spectrum of the quercetin reaction product with corresponding authentic 3'-methylated and 4'-methylated compounds showed that the methylation position was at either the 3'-hydroxyl or 4'-hydroxyl group. Thus, BcOMT-2 transfers a methyl group either to the 3'-hydroxyl or 4'-hydroxyl group of flavonoids when both hydroxyl groups are available. Among several flavonoids that contain a 3'- and 4'-hydroxyl group, fisetin was the best substrate for the BcOMT-2.

• Korean Journal of Food Science and Technology
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• v.31 no.3
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• pp.815-822
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• 1999

Twenty one flavonoids were isolated from ethyl acetate layer of aqueaus EtOH extracts of Artemisia vulgaris and identified as tricin, jaceosidine, eupafolin, diosmetin, chrysoeriol, homoeriodictyol, isorhamnetin, apigenin, eriodictyol, luteolin, luteolin 7-glucoside, kaempferol 3-glucoside, kaempferol 7-glucoside, kaempferol 3-rhamnoside, kaempferol 3-rutinside, quercetin, quercetin 3-glucoside, quercetin 3-galactoside, quercetrin, quercetin 7-glucoside, rutin, and vietexin. The inhibitory activity for all purified flavonoids were examined against lipid peroxidation in rat liver microsome. All examined flavonoids showed considerable antioxidant activity. Among them, $IC_{50}$ value of apigenin, luteolin, isorhamnetin, quercetin, and eriodictyol were showed higher than that of vitamin E used as positive control. And methoxylated flavonoids, tricin, eupafolin, jaceosidine, diosmetin, and isorhamnetin showed considerable antioxidant activity. Each $IC_{50}$ values were shown at 0.9, 1.0, 1.4, 1.0, and $0.7\;{\mu}g/mL$, respectively.

• Korean Journal of Poultry Science
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• v.42 no.1
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• pp.33-40
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• 2015

This study was conducted to investigate the effects of dietary quercetin on growth performance, blood biochemical parameters, immunoglobulin, and blood antioxidant activity in broiler chickens. Three hundred twenty one-day old Ross broilers were divided 8 treatments (C(-), basal diet; C(+), basal diet with antibiotics; vitamin E 20 IU; vitamin E 200 IU; quercetin 20 ppm; quercetin 200 ppm; methoxylated quercetin 20 ppm; methoxylated quercetin 200 ppm) with 4 replicates and 10 birds per replicate. Birds were reared for 35 days and their feed intake and weight gain were measured weekly. At 35d, eight birds of average weight from each replicate were selected for blood collection and analysis. Weight gain of birds in the groups fed quercetin was higher when compare to NC but there was no significant difference. In the serum, creatinine, BUN and AST in quercetin groups significantly decreased compared to those of control (NC and PC) (P<0.05). The contents of IgA and IgM were significantly lower in quercetin groups than those of NC (P<0.05). SOD like activity and MDA content tended to decrease in quercetin groups, however, there was no significant difference among treatments. In conclusion, supplemental quercetin to poultry diet could be positive aspect on performance and blood metabolites. Optimum adding levels was more than 20 ppm.

• Journal of Microbiology and Biotechnology
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• v.20 no.9
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• pp.1359-1366
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• 2010

A search of the Streptomyces avermitilis genome reveals that its closest homologs are several O-methyltransferases. Among them, one gene (viz., saomt5) was cloned into the pET-15b expression vector by polymerase chain reaction using sequence-specific oligonucleotide primers. Biochemical characterization with the recombinant protein showed that SaOMT5 was S-adenosyl-L-methionine-dependent Omethyltransferase. Several compounds were tested as substrates of SaOMT5. As a result, SaOMT5 catalyzed O-methylation of flavonoids such as 6,7-dihydroxyflavone, 2',3'-dihydroxyflavone, 3',4'-dihydroxyflavone, quercetin, and 7,8-dihydroxyflavone, and phenolic compounds such as caffeic acid and caffeoyl Co-A. These reaction products were analyzed by TLC, HPLC, LC/MS, and NMR spectroscopy. In addition, SaOMT5 could convert phenolic compounds containing ortho-dihydroxy groups into O-methylated compounds, and 6,7-dihydroxyflavone was known to be the best substrate. SaOMT5 converted 6,7-dihydroxyflavone into 6-hydroxy-7-methoxyflavone and 7-hydroxy-6-methoxyflavone, and caffeic acid into ferulic acid and isoferulic acid, respectively. Moreover, SaOMT5 turned out to be a $Mg^{2+}$-dependent OMT, and the effect of $Mg^{2+}$ ion on its activity was five times greater than those of $Ca^{2+}$, $Fe^{2+}$, and $Cu^{2+}$ ions, EDTA, and metal-free medium.