kaempferide and galangin

Zika virus (ZIKV) infection is a global public health problem due to its rapid spread and the possibility of causing microcephaly. Currently, no specific antivirals against ZIKV are available for treatment. In the present study, several flavonoids (galangin, kaempferide, quercetin, myricetin and EGCG) were found to reduce ZIKV induced plaques and viral RNA copies with negligible cytotoxic effects on host cells. In addition, inhibition of ZIKV propagation by flavonoids showed structure-activity relationship. Our results demonstrate flavonoids as inhibitors of ZIKV entry and NS2B-NS3 protease. Hence, these flavonoids could be used as potential bifunctional drugs for treating ZIKV infections.

Topics: Animals; Antiviral Agents; Chlorocebus aethiops; Flavonoids; Humans; Kaempferols; Molecular Structure; Quercetin; Serine Endopeptidases; Structure-Activity Relationship; Vero Cells; Viral Nonstructural Proteins; Viral Proteins; Virus Internalization; Virus Replication; Zika Virus; Zika Virus Infection

Galangal extract (GE)-based hypouricemic functional food is under-developed due to ambiguous quality control standard that is closely associated with action mechanisms and interaction of key xanthine oxidase (XO) inhibitors (kaempferide and galangin) in GE. In terms of kinetics analysis, fluorescence quenching and molecular docking, kaempferide and galangin showed similar docking posture to xanthine in molybdopterin center, and formed flavonol-XO complexes driven by hydrogen bonding, hydrophobic interaction and van der Waals force, competitively inhibiting XO. Kaempferide, had stronger binding affinity for XO and three more hydrogen bonds with XO than galangin, interacting with critical amino acid residues (Arg880 and Glu802) in catalysis reaction of XO and showing stronger XO inhibitory activity than galangin. The combination of kaempferide and galangin enhanced their binding affinities for XO, showing synergistic inhibition on XO at optimal molar ratio 1:4 that could be quality control standard for GE. This study provided new insights into structure-XO inhibitory activity relationship of methoxylated flavonoids and quality control standard for GE-based hypouricemic functional food.

Topics: Alpinia; Binding Sites; Enzyme Activation; Enzyme Inhibitors; Flavonoids; Hydrophobic and Hydrophilic Interactions; Kaempferols; Kinetics; Molecular Conformation; Molecular Docking Simulation; Molecular Dynamics Simulation; Plant Extracts; Protein Binding; Structure-Activity Relationship; Thermogravimetry; Xanthine Oxidase

Flavonoids are polyphenolic compounds required in the fertilization process in many, if not all, plants. However, the exact biological mechanism(s) and the interacting proteins are unknown. To determine the characteristics important in activating or inhibiting the pollination sequence, a structure-activity relationship analysis of natural and synthetic flavonols was conducted. Flavonol analogues were synthesized through a modified "one-pot" procedure that utilized a Baker-Venkataraman type rearrangement and a Suzuki-Miyaura cross-coupling of a halo-flavonol with an organotrifluoroborate. Of the flavonols tested, kaempferol was the only compound to act as a full agonist. The other smaller, less sterically hindered flavonols (galangin, kaempferide, and 4'-methyl flavonol) acted as partial agonists. Larger more hydrophobic flavonol analogues (3'- and 4'-benzoyl, 3'- and 4'-phenyl, and 3'- and 4'-iodo flavonols) had minimal or no agonist activity. Competition assays between kaempferol and these minimally activating flavonols showed that these analogues inhibited the action of kaempferol in a manner consistent with noncompetitive antagonism. The results suggest that steric hindrance is the most important factor in determining a good agonist. Hydrogen bonding also had a positive effect as long as the substituent did not cause any steric hindrance.

Topics: Chemistry Techniques, Synthetic; Flavonoids; Flavonols; Germination; Hydrogen Bonding; Kaempferols; Petunia; Plants, Genetically Modified; Pollen; Structure-Activity Relationship

The smaller galangal is extracted, purified and identified the bioactive compounds. The purpose of this research was to investigate whether these isolated compounds have antibacterial and synergistic activity against amoxicillin-resistant Escherichia coli (AREC) when used singly and in combination with amoxicillin. The primarily mode of action is also studied.. The galangin, kaempferide and kaempferide-3-O-β-d-glucoside were isolated. The minimum inhibitory concentrations(MIC) of amoxicillin and these flavonoids against AREC were between 500 and >1000 μg ml(-1). Synergistic activity was observed on combining amoxicillin with these flavonoids. The combinations of amoxicillin and these flavonoids exhibited a synergistic effect, reducing AREC cell numbers. Electron microscopy showed that these combinations damaged the ultrastructure of AREC cells. The results indicated that these combinations altered outer membrane permeability but not affecting cytoplasmic membrane. Enzyme assays showed that these flavonoids had an inhibitory activity against penicillinase.. These results indicated that these flavonoids have the potential to reverse bacterial resistance to amoxicillin in AREC and may operate via three mechanisms: inhibition of peptidoglycan and ribosome synthesis, alteration of outer membrane permeability, and interaction with β-lactamases.. These findings offer the potential to develop a new generation of phytopharmaceuticals to treat AREC.

Topics: Alpinia; Amoxicillin; Anti-Bacterial Agents; beta-Galactosidase; Cell Membrane; Cell Membrane Permeability; Drug Resistance, Bacterial; Drug Synergism; Enzyme Activation; Escherichia coli; Flavonoids; Kaempferols; Microbial Sensitivity Tests; Rhizome

The 80% aqueous acetone extract from the rhizomes of Alpinia officinarum, a Chinese medicinal herb, were found to inhibit melanogenesis in theophylline-stimulated murine B16 melanoma 4A5 cells. Among the constituents isolated, four diarylheptanoids [5-hydroxy-1,7-diphenyl-3-heptanone, 7-(4('')-hydroxy-3('')-methoxyphenyl)-1-phenylhept-4-en-3-one, 5-hydroxy-7-(4('')-hydroxy-3('')-methoxyphenyl)-1-phenyl-3-heptanone, and 3,5-dihydroxy-1,7-diphenylheptane] and two flavonol constituents (kaempferide and galangin) inhibited melanogenesis with IC(50) values of 10-48microM, and several structural requirements of the active constituents for the inhibition were clarified. In addition, 7-(4('')-hydroxy-3('')-methoxyphenyl)-1-phenylhept-4-en-3-one, kaempferide, and galangin inhibited mRNA expression of tyrosinase and tyrosinase-related proteins-1 and -2, and the protein level of a microphthalmia-associated transcription factor.

Topics: Alpinia; Animals; Antineoplastic Agents; Enzyme Inhibitors; Flavonoids; Kaempferols; Melanoma, Experimental; Mice; Monophenol Monooxygenase; Oxidoreductases; Rhizome

There is very limited information on cytochrome P450 (P450)-mediated oxidative metabolism of dietary flavonoids in humans. In this study, we used human liver microsomes and recombinant P450 isoforms to examine the metabolism of two flavonols, galangin and kaempferide, and one flavone, chrysin. Both galangin and kaempferide, but not chrysin, were oxidized by human liver microsomes to kaempferol, with K(m) values of 9.5 and 17.8 microM, respectively. These oxidations were catalyzed mainly by CYP1A2 but also by CYP2C9. Consistent with these observations, the human liver microsomal metabolism of galangin and kaempferide were inhibited by the P450 inhibitors furafylline and sulfaphenazole. In addition, CYP1A1, although less efficient, was also able to oxidize the two flavonols. Thus, dietary flavonols are likely to undergo oxidative metabolism mainly in the liver but also extrahepatically.

Topics: Aryl Hydrocarbon Hydroxylases; Cytochrome P-450 CYP1A1; Cytochrome P-450 CYP1A2; Cytochrome P-450 CYP2C9; Cytochrome P-450 Enzyme System; Flavonoids; Humans; Isoenzymes; Kaempferols; Microsomes, Liver; Mutagens; Oxidation-Reduction; Quercetin; Steroid 16-alpha-Hydroxylase; Steroid Hydroxylases; Trisaccharides

Starting from the interaction of galangin (3,5,7-trihydroxyflavone) with a cytosolic nucleotide-binding domain of P-glycoprotein, a series of flavonol derivatives was synthesized and tested for their binding affinity towards the same target. The 5,7-dihydroxy-4'-iodoflavonol and 5,7-dihydroxy-4'-n-octylflavonol derivatives displayed much higher binding affinities, with respective increases of 6- and 93-fold as compared to galangin.

Topics: ATP Binding Cassette Transporter, Subfamily B, Member 1; Binding Sites; Chalcone; Drug Resistance, Multiple; Flavonoids; Flavonols; Fluorescence; Kaempferols; Molecular Structure; Protein Binding; Protein Structure, Tertiary; Quercetin; Recombinant Proteins; Thermodynamics; Tryptophan