New antimicrobial flavanones from Physena madagascariensis

Methylene-bridged dimeric natural products involving one-carbon unit in biosynthesis

This review summarizes the methylene-bridged dimeric natural products involving one-carbon unit in biosynthesis, including their structures, biological activities, synthetic methods, and formation mechanisms.

Chemodiversity Studies on Exudate Flavonoids of Cleomaceae species (Brassicales)

Seven species of the genus Cleome were analysed for formation of exudate flavonoids. The majority of structures found were polymethoxyflavonols with 6- and/or 8- O-substitution. A novel compound, isolated from C. felina, was determined to be 5,3′,4′-triOH-3,6,7,5′-tetraOMe-flavone (1), and a further novel compound, 5,3′-diOH-3,7,8,4′,5′-pentaOMe-flavone (3), was isolated from C. viscosa. Flavones with corresponding substitution have primarily been found in C. droserifolia. Rather simple flavanones such as naringenin-7-Me have so far been found only in one accession of C. hassleriana. The flavonoid profiles of the newly studied species and accessions are discussed in relation to phytochemical, taxonomical and pharmacological data.

Theoretical Study about the Effect of Halogen Substitution on the Reactivity of Antitumor 3-Formylchromones and Their Free Radicals

The mandatory presence of a chlorine atom on the aromatic ring of 6-hydroxy-3-formyl angular chromones, on the respiration inhibition of mammary carcinoma mouse, is explained through a computational study of these compounds. This study analyzes the reactivity of the neutral molecules and their free radicals, in gas phase and with water solvation, incorporated by the polarizable continuum medium (PCM) approach. Electrophilic reactivities were evaluated using Fukui (f+) and Parr (P+) functions. The stabilities of radical species formed by the abstraction of a hydrogen atom from the O-H bond were evaluated by bond dissociation enthalpy (BDE) and spin density (SD) calculations. This study has potential implications for the design of chromone analogues as anticancer compounds.

Crystal structure of 4-(6-chloro-4-oxo-4H-chromen-3-yl)-2-methyl-amino-3-nitro-4H,5H-pyrano[3,2-c]chromen-5-one chloro-form monosolvate

In the title compound, C23H14Cl4N2O7, the pyran ring has an envelope conformation with the methine C atom as the flap. The chromene rings are almost planar (r.m.s. deviations of 0.027 and 0.018 Å) and their mean planes are inclined to one another by 85.61 (10)°. The mean planes of the pyran ring and the chromene ring fused to it are inclined to one another by 7.41 (13)°. The mol-ecular structure is stabilized by an intra-molecular N-H⋯O hydrogen bond, generating an S(6) ring motif. In the crystal, mol-ecules are linked by pairs of N-H⋯O hydrogen bonds, forming inversion dimers with an R (2) 2(12) ring motif. The dimers are linked by pairs of C-H⋯O hydrogen bonds, enclosing R (2) 2(18) ring motifs, forming chains along [010]. Within the chains there are C-H⋯π inter-actions. The chains are linked via slipped parallel π-π inter-actions, forming a three-dimensional structure [the shortest inter-centroid distance is 3.7229 (19) Å].

Chemical constituents isolated from the Mongolian medicinal plant Sophora alopecuroides L. and their inhibitory effects on LPS-induced nitric oxide production in RAW 264.7 macrophages

Three new flavonostilbenes, alopecurones M-O (1-3), were isolated from the root bark of Sophora alopecuroides L. together with 21 known compounds. The structures of the isolated compounds were elucidated by using NMR, MS, and CD spectroscopic data. All isolates were evaluated for their potential to inhibit LPS-induced nitric oxide production in RAW 264.7 cells.

Spectroscopic (FT-IR and FT-Raman) investigation, first order hyperpolarizability, NBO, HOMO-LUMO and MEP analysis of 6-nitrochromone by ab initio and density functional theory calculations

The vibrational spectral analysis is carried out using FT-Raman and FT-IR spectroscopy in the range 3500-50 cm(-1) and 4000-400 cm(-1), respectively, for 6-nitrochromone (6NC). The molecular structure, fundamental vibrational frequencies and intensity of the vibrational bands are interpreted with the aid of structure optimization and normal coordinates force field calculation based on ab initio HF and DFT gradient calculations employing the HF/6-311++G(d,p) and B3LYP/6-311++G(d,p) basis set. Stability of the molecule has been analyzed using NBO analysis. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. Thermodynamic properties like entropy, heat capacity, zero-point energy and Mulliken's charge analysis have been calculated for the 6NC. The complete assignments were performed on the basis of total energy distribution (TED) of the vibrational modes with scaled quantum mechanical (SQM) method. The MEP map shows the negative potential sites are on oxygen atoms as well as the positive potential sites are around the hydrogen atoms.

Two structurally distinct chalcone dimers from Helichrysum zivojinii and their activities in cancer cell lines

Dimers tomoroside A (1) and tomoroside B (2) of the co-occuring known chalcone monomer (3), along with the seven known flavonoid glucosides (4-10), were isolated from the aerial parts of Helichrysum zivojinii Černjavski & Soška. The structures of the isolated compounds were elucidated by spectroscopic techniques. Compound 1 inhibited topo IIα and hif-1α expression and stimulated doxorubicin anticancer effect, while 2 increased the expression of hif-1α, probably acting as antioxidant and redox status modulator. Notably, 2 synergized with Tipifarnib showing potential to improve the action of this new chemotherapeutic involved in the modulation of mitogene activated protein (MAP) kinase signaling pathway.

Physiochemical, optical and biological activity of chitosan-chromone derivative for biomedical applications

This paper describes the physiochemical, optical and biological activity of chitosan-chromone derivative. The chitosan-chromone derivative gels were prepared by reacting chitosan with chromone-3-carbaldehyde, followed by solvent exchange, filtration and drying by evaporation. The identity of Schiff base was confirmed by UV-Vis absorption spectroscopy and Fourier-transform infrared (FTIR) spectroscopy. The chitosan-chromone derivative was evaluated by X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), photoluminescence (PL) and circular dichroism (CD). The CD spectrum showed the chitosan-chromone derivative had a secondary helical structure. Microbiological screening results demonstrated the chitosan-chromone derivative had antimicrobial activity against Escherichia coli bacteria. The chitosan-chromone derivative did not have any adverse effect on the cellular proliferation of mouse embryonic fibroblasts (MEF) and did not lead to cellular toxicity in MEFs. These results suggest that the chitosan-chromone derivative gels may open a new perspective in biomedical applications.

Palladium-catalyzed cascade reactions of coumarins with alkynes: synthesis of highly substituted cyclopentadiene fused chromones

A palladium-catalyzed cascade reaction of coumarins with alkynes is described, which provides a new route to the synthesis of highly substituted cyclopentadiene fused chromones.

Cytotoxic 16-beta-[(D-xylopyranosyl)oxy]oxohexadecanyl triterpene glycosides from a Malagasy plant, Physena sessiliflora

Brine shrimp lethality assay-guided separation of the MeOH extract of leaves of Physena sessiliflora, which is endemic to Madagascar, afforded eight triterpene glycosides, Physenoside S1-4 and 16-beta-[(d-xylopyranosyl)oxy]oxohexadecanyl homologues, Physenoside S5-8. Structural elucidation of these compounds was based on both spectroscopic analyses and chemical properties. Physenoside S7 and S8 have significant cytotoxic activities in the brine shrimp lethality assay.

Naturally Occurring Flavanones: An Overview

Flavanones are one of the most interesting naturally occurring flavonoids in view of their structural pattern as well as biological and pharmacological potentials. The present review deals with natural flavanones reported from 1998 to mid 2007, along with their biological and pharmacological activities. The review includes more than 160 new naturally occurring flavanones from 135 references. The reported flavonoids belong to thirty-six plant families.

Effects of Simple and Angular Chromones on Tumor Cell Respiration

A set of structurally related compounds incorporating a chromone moiety as an essential component of their structures were tested against the TA3 mouse carcinoma cell line and its multidrug-resistant variant TA3-MTX-R. A tentative structure–activity relationship was found for this family of substances, suggesting that a Michael addition at C-1 is involved in the mechanism that provokes the activities.

A Pyranochalcone and Prenylflavanones from Tephrosia pulcherrima (Baker) Drumm

A new 2′,6′-dimethoxy-4′,5′-(2″,2″-dimethyl)-pyranochalcone (1) and three known flavanones, namely 5-hydroxy-7-methoxy-8-(3,3-dimethylallyl)-flavanone (methyl glabranin) (2), 5,7-dimethoxy-8-(3,3-dimethylallyl)-flavanone (candinone) (3) and 5- O-methyl obovatin (pongachin) (4), have been isolated from the chloroform extract of the roots of Tephrosia pulcherrima. The flavonoids were fully characterized by detailed 1D- and 2D-NMR spectroscopic investigations. The pyranochalcone 1 showed significant antimicrobial activity when tested against a series of micro-organisms.

A chromone analog inhibits TNF-alpha induced expression of cell adhesion molecules on human endothelial cells via blocking NF-kappaB activation

The interaction between leukocytes and the vascular endothelial cells (EC) via cellular adhesion molecules plays an important role in various inflammatory and immune diseases. The molecules that block these interactions have been targeted as potential therapeutic targets for acute and chronic inflammatory diseases. In an effort to develop potent cell adhesion molecule inhibitors, a series of chromone derivatives bearing alkoxycarbonylvinyl unit at the C-3 position, that is, the chromones 8a-d and 9a-d, were designed and synthesized, and evaluated for their ICAM-1 inhibitory activity on human endothelial cells as well as their effect on NADPH-catalyzed rat microsomal lipid peroxidation. A structure-activity relationship was established and we found that length of the alkyl moiety of the chromone-3-yl-acrylate is important for this activity. Further, we found that incorporation of unsaturation in the alcohol moiety increases the potential of the compound for the inhibition of TNF-alpha induced expression of ICAM-1 and also for the inhibition of lipid peroxidation. Out of the screened compounds, the most potent compound ethyl trans-3-(4-oxo-4H-1-benzopyran-3-yl)-acrylate (8a) was taken for further study. We have found that compound 8a also significantly inhibited the TNF-alpha induced expression of VCAM-1 and E-selectin, which play key roles in various inflammatory diseases. This inhibition was found to be concentration dependent. The functional consequences of inhibiting cell adhesion molecules were studied by performing cell-adhesion assay. We found that compound 8a significantly blocks the adhesion of neutrophils to endothelial monolayer. To elucidate the molecular mechanism of inhibition of cell adhesion molecules, we investigated the status of nuclear transcription factor-kappaB (NF-kappaB) and were able to establish that compound 8a significantly blocked the TNF-alpha induced activation of NF-kappaB.

Cytotoxic compounds of Physena madagascariensis from the Madagascar rain forest paragraph sign

Two new flavanones, remangiflavanones D and E (1 and 2), were isolated from an extract of the twigs, leaves, and flowers of Physena madagascariensis together with three known flavanones, remangiflavanones A-C (3-5), and (E)-N-feruloyltyramine (6). The structures of the new compounds 1 and 2 were established on the basis of one-dimensional and two-dimensional NMR spectroscopic data interpretation. All compounds were evaluated for their cytotoxicity in the A2780 human ovarian cancer cell line. Compound 5 was the most active with an IC50 value of 2.5 microg mL-1.

Antimicrobial activity of flavonoids

Flavonoids are ubiquitous in photosynthesising cells and are commonly found in fruit, vegetables, nuts, seeds, stems, flowers, tea, wine, propolis and honey. For centuries, preparations containing these compounds as the principal physiologically active constituents have been used to treat human diseases. Increasingly, this class of natural products is becoming the subject of anti-infective research, and many groups have isolated and identified the structures of flavonoids possessing antifungal, antiviral and antibacterial activity. Moreover, several groups have demonstrated synergy between active flavonoids as well as between flavonoids and existing chemotherapeutics. Reports of activity in the field of antibacterial flavonoid research are widely conflicting, probably owing to inter- and intra-assay variation in susceptibility testing. However, several high-quality investigations have examined the relationship between flavonoid structure and antibacterial activity and these are in close agreement. In addition, numerous research groups have sought to elucidate the antibacterial mechanisms of action of selected flavonoids. The activity of quercetin, for example, has been at least partially attributed to inhibition of DNA gyrase. It has also been proposed that sophoraflavone G and (-)-epigallocatechin gallate inhibit cytoplasmic membrane function, and that licochalcones A and C inhibit energy metabolism. Other flavonoids whose mechanisms of action have been investigated include robinetin, myricetin, apigenin, rutin, galangin, 2,4,2'-trihydroxy-5'-methylchalcone and lonchocarpol A. These compounds represent novel leads, and future studies may allow the development of a pharmacologically acceptable antimicrobial agent or class of agents.