Chromenylchalcones with inhibitory effects on monoamine oxidase B.

Structure-activity relationship (SAR) calculations were used to find monoamine oxidase-B (MAO-B) inhibitors by identifying pharmacophores exhibiting high inhibitory activities. Several such chromenylchalcones were designed and synthesized accordingly. Their inhibitory effects on MAO-B were determined using an HPLC-based method and an MAO-B enzyme assay kit. (E)-3-(6-Methoxy-2H-chromen-3-yl)-1-(2-methoxyphenyl)prop-2-en-1-one exhibited a half-maximal inhibitory concentration of 320 nM. Its molecular-level binding mode with the three-dimensional structure of MAO-B was elucidated using an in silico docking study. The chromenylchalcone scaffold, which is derived from natural products including isoflavonoids and chalcones, had not been previously reported as an MAO-B inhibitor.

1H and 13C NMR spectral assignments of 2'-hydroxychalcones.

Chalcones are of interest to medicinal chemists because their structures can be easily modified with various functional groups. The syntheses and biological activities of chalcones from natural sources are well known. In this study, 24 2'-hydroxychalcones bearing methoxy substituents were synthesized, among which five are new. The NMR data for all synthesized chalcones are described for the first time. The complete assignments of the (1)H and (13)C NMR data can be used for the identification of newly discovered and widely isolated, synthesized chalcones.

Synthesis of methoxybenzoflavones and assignments of their NMR data.

A phytotoxic root exudate from Acroptilon repens was identified as 7,8-benzoflavone, an inhibitor of cytochrome P450 1A2 and activator of cytochrome P450 3A4. The synthetic 5,6-benzoflavone also is a potent phytotoxin. Six 7,8-benzoflavones and eight 5,6-benzoflavones were synthesized in this study. The NMR data for a few of these compounds have been previously reported; however, the NMR data for most of them have not been reported. For reference purposes, the complete NMR data for the 14 benzoflavones are described.

1H and 13C NMR spectral assignments of novel chromenylchalcones.

Several types of chalcones containing 2H-chromen group were synthesized. Claisen-Schmidt condensation of 2H-chromen-3-carbaldehydes (I) with methoxy substituted acetophenones afforded (E)-3-(2H-chromen-3-yl)-1-(methoxyphenyl)prop-2-en-1-ones (chromenylchalcones, 1-7). Other types of chromenylchalcone, (E)-1-(6-methoxy-2H-chromen-3-yl)-3-(methoxyphenyl)prop-2-en-1-ones (8-13) were also obtained between reaction of methoxy substituted benzaldehydes and 1-(6-methoxy-2H-chromen-3-yl)ethanone (II). Dichromenylchalcones (14-16) were also synthesized through the same reaction between aldehydes (I) and ketone (II). Their complete (1)H-NMR and (13)C-NMR assignments are reported here and more polysubstituted chromenylchalcones synthesized or isolated from the natural sources in the future can be identified on the basis of the NMR data reported here.

Synthesis and complete assignment of NMR data of 20 chalcones.

Chalcones, intermediates in flavonoid biosynthesis, can exhibit antibacterial, antiproliferative, and anti-inflammatory properties. Chalcones contain two benzene rings and both hydroxylated and methoxylated analogs are frequently produced by hydroxylases and O-methyltransferases in plant biosynthetic pathways. Assignments of NMR peaks in the spectra of hydroxylated and/or methoxylated chalcones can help in identifying novel chalcone derivatives isolated from natural sources by referencing these data against NMR spectra obtained from known chalcones. We report here the syntheses of 20 chalcones and complete assignments of (1)H and (13)C NMR spectra.

Complete NMR data of methoxylated cis- and trans-stilbenes as well as 1,2-diphenylethanes.

Resveratrol is a polyphenol isolated from many natural sources including grapes, mulberries, eucalyptus, spruce, lilies, and peanuts. The hydroxyl groups in polyphenols can be substituted with various functional groups, allowing production of multiple derivatives. NMR spectroscopy is used to identify new derivatives. Since the complete NMR data of the known derivatives can be useful for identification of the newly isolated derivatives, here, we report the synthesis of 14 methoxylated stilbenes and four 1,2-diphenylethanes and their NMR data.

Relationships between structures of hydroxyflavones and their antioxidative effects.

Even hydroxyflavones show diverse biological functions, they have two common features such as showing antioxidative effects and containing hydroxyl groups. The authors tested the antioxidative effects of thirty hydroxyflavones using 1,1-diphenyl-2-picrylhydrazyl radical scavenging assay. While the scavenging activity of galangin, 3,5,7-trihydroxyflavone was 52.5%, fisetin, 3,7,3',4'-tetrahydroxyflavone showed 85.2%. To investigate the relationships between the structures of hydroxyflavones and their antioxidative effects, the three-dimensional quantitative structure-activity relationships were examined.

Characterization of an O-methyltransferase from Streptomyces avermitilis MA-4680.

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 Omethylation 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 Omethylated 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 Mg2+-dependent OMT, and the effect of Mg2+ ion on its activity was five times greater than those of Ca2+, Fe2+, and Cu2+ ions, EDTA, and metal-free medium.

In silico study of the ion channel formed by tolaasin I produced by Pseudomonas tolaasii.

A toxin produced by Pseudomonas tolaasii, tolaasin, causes brown blotch disease in mushrooms. Tolaasin forms pores on the cellular membrane and destroys cell structure. Inhibiting the ability of tolaasin to form ion channels may be an effective method to protect against attack by tolaasin. However, it is first necessary to elucidate the three-dimensional structure of the ion channels formed by tolaasin. In this study, the structure of the tolaasin ion channel was determined in silico based on data obtained from nuclear magnetic resonance experiments.