Among the flavonols in green tea, kaempferol has many biological activities but kaempferol of plant origin is too expensive to be used in commercial products. Recently, we confirmed that green tea seed (GTS) contained a reasonable amount of kaempferol glycoside. After conducting structure analysis, two kaempferol glycosides were identified, kaempferol-3-O-[2-O-beta-D-galactopyranosyl-6-O-alpha-L-rhamnopyranosyl]-beta-D-glucopyranoside (compound 1) and kaempferol-3-O-[2-O-beta-D-xylopyranosyl-6-O-alpha-L-rhamnopyranosyl]-beta-D-glucopyranoside (compound 2), respectively. Also, a commercially useful method for kaempferol preparation was suggested by enzymatic hydrolysis using these two flavonoids. After several enzyme reactions were performed for the complete bioconversion of compounds 1 and 2 to kaempferol, we found that the optimum enzyme combination was reaction with beta-galactosidase and hesperidinase. Finally, we produced pure kaempferol with over 95% purity. We also compared the antioxidant effect of these two GTS flavonoids and its aglycone, kaempferol. Kaempferol is a more efficient scavenger of 1,1-diphenyl-2-picrylhydrazyl radicals and a better inhibitor of xanthine/xanthine oxidase than the two glycosides.
The objective of this study was to examine the biological activity of kaempferol and its rhamnosides. We isolated kaempferol (1), α-rhamnoisorobin (2), afzelin (3), and kaempferitrin (4) as pure compounds by far-infrared (FIR) irradiation of kenaf (Hibiscus cannabinus L.) leaves. The depigmenting and anti-inflammatory activity of the compounds was evaluated by analyzing their structure-activity relationships. The order of the inhibitory activity with regard to depigmentation and nitric oxide (NO) production was kaempferol (1) > α-rhamnoisorobin (2) > afzelin (3) > kaempferitrin (4). However, α-rhamnoisorobin (2) was more potent than kaempferol (1) in NF-κB-mediated luciferase assays. From these results, we conclude that the 3-hydroxyl group of kaempferol is an important pharmacophore and that additional rhamnose moieties affect the biological activity negatively.
At present, there is much interest in organocatalysts, as they tend to be less toxic and more environmentally friendly than traditional metal-based catalysts.[1] Although much progress has been made, [2] the development of chiral organocatalysts that are as reactive and stereoselective as some of the best transition-metal catalysts remains a considerable challenge. To attain reasonable reaction rates and stereoselectivity with organocatalysts, a large catalyst loading is often required. One way to address this difficulty is to design bifunctional or multifunctional organocatalysts [3] with functional groups that work cooperatively to stabilize the transition state and accelerate the rate of the reaction. It has been shown that urea-or thiourea-based bifunctional organocatalysts are effective in facilitating a variety of useful organic reactions, [4] including the methanolytic desymmetrization of cyclic anhydrides. [5,6] However, we showed recently that urea-and thiourea-based organocatalysts can form hydrogen-bonded aggregates, which results in a strong dependence of reactivity and enantioselectivity on concentration and temperature. [5] X-ray crystal structures of monofunctional and bifunctional (thio)urea derivatives show that they form aggregates through hydrogen bonding between the (thio)urea NH groups and the (thio)urea sulfur or oxygen atom in an intermolecular fashion.[7] A recent NMR spectroscopic study also showed that the thiourea IV exists as a dimer, even in solution.[8] Furthermore, thiourea groups tend to degrade under thermal conditions.[9]Herein we present a thermally robust sulfonamide-based bifunctional organocatalyst I (Scheme 1), [10] which shows unprecedented catalytic activity and excellent enantioselectivity in the methanolytic desymmetrization [11] of meso cyclic anhydrides. A detailed mechanistic and computational approach to the design of I resulted in a catalyst that does not self-aggregate to any appreciable extent. To the best of our knowledge, I is the first quinine-and sulfonamide-based bifunctional organocatalyst. The quinuclidine group of I may be able to function as a general-base catalyst to activate the nucleophile, [12] and the sulfonamide group [13] may be able to activate the electrophile simultaneously by hydrogen bonding.To investigate the catalytic activity and enantioselectivity of the cinchona-alkaloid-based sulfonamide catalyst I, we examined the asymmetric methanolysis of cis-1,2-cyclohexanedicarboxylic anhydride (1 a) in Et 2 O with various amounts of I at ambient temperature. The results are summarized in Table 1, together with the results obtained with other cinchona-alkaloid-based catalysts (quinine (II), (DHQ) 2 AQN (III), and the quinine-based thiourea catalyst IV; Scheme 1). The desymmetrization of 1 a with I (10 mol %) proceeded surprisingly fast; the reaction was complete within 1 h to Scheme 1. Structures of cinchona-alkaloid-based organocatalysts.
Ginsenoside (G) Rp1 is a ginseng saponin derivative with anti-cancer and anti-inflammatory activities. In this study, we examined the mechanism by which G-Rp1 inhibits inflammatory responses of cells. We did this using a strategy in which DNA constructs containing cyclooxygenase (COX)-2 and inducible nitric oxide synthase (iNOS) promoters were transfected into HEK293 cells. G-Rp1 strongly inhibited the promoter activities of COX-2 and iNOS; it also inhibited lipopolysaccharide induced upregulation of COX-2 and iNOS mRNA levels in RAW264.7 cells. In HEK293 cells G-Rp1 did not suppress TANK binding kinase 1-, Toll-interleukin-1 receptor-domain-containing adapter-inducing interferon-β (TRIF)-, TRIFrelated adaptor molecule (TRAM)-, or activation of interferon regulatory factor (IRF)-3 and nuclear factor (NF)-кB by the myeloid differentiation primary response gene (MyD88)-induced. However, G-Rp1 strongly suppressed NF-кB activation induced by IкB kinase (IKK)β in HEK293 cells. Consistent with these results, G-Rp1 substantially inhibited IKKβ-induced phosphorylation of IкBɑ and p65. These results suggest that G-Rp1 is a novel anti-inflammatory ginsenoside analog that can be used to treat IKKβ/NF-кB-mediated inflammatory diseases.
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