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Four new flavone derivatives (1–4), together with six known flavones (5-10), were isolated from the stems of Dracaena angustifolia. The complete structures of new compounds were elucidated by analyses of spectroscopic data and quantum chemistry calculations. Compounds 2, 9 and 10 displayed weak anti-inflammatory activity with IC50 values of 45, 33 and 61 μM, respectively.

Tosyloxy- and mesyloxyflavones derived from abundant and biologically important hydroxyflavones were used to synthesize a series of functionalized flavones through versatile palladium-catalyzed cross-coupling reactions. A Pd(OAc)2/2-[2-(dicyclohexylphosphino)phenyl]-1-methyl-1H-indole system effectively catalyzed the reactions of a broad range of tosyloxy- and mesyloxyflavones as electrophilic coupling partners with various nucleophiles to give the corresponding products in good to excellent yields. Catalyst loadings of as little as 0.1 mol% Pd were successfully used. Importantly, we demonstrated that this protocol provided a significantly improved efficiency in the synthesis of a potential chromen-4-one-based analogue of a potent inhibitor of DNA-dependent protein kinase.

Carbonylative Sonogashira annulation sequence for one pot synthesis of 4-quinolone and 4H-chromen-4-one has been developed in presence of Pd-NHC catalyst. Substituted 2-iodoaniline and 2-iodophenol independently underwent in the carbonylative Sonogashira annulation reaction with a variety of acetylenes to result in 4-quinolone and flavone derivatives respectively in good to excellent yield. Moreover, this protocol does not require toxic CO gas, high catalyst loading and any expensive salt/additive. Herein we, for the first time, are using Mo(CO)6, as solid CO source for the one pot synthesis of flavone derivatives via carbonylative Sonogashira annulation reaction.

A series of flavones were synthesized from 2-hydroxyacetophenones using a modified Baker–Venkataraman reaction. The 2-hydroxyacetophenone, 2,4-dihydroxyacetophenone, or 2,5-dihydroxyacetophenone, or 2,6-dihydroxyacetophenone was treated with 2 equiv of a 4-substituted aroyl chloride in 99:1 (w/w) acetone/water using both K2CO3 (8 equiv) and pyridine (4 equiv) as bases. Various 4′-substituted (R=H, Me, Cl, F) flavone derivatives were obtained via this one-pot procedure in high yield (≥70%). This modified process is both simple and efficient. Compound 26b (3-(4-fluorobenzoyl)-5-hydroxy-4′-fluoroflavone) was synthesized for the first time with a yield of 12%. The method was unsuccessful, however, for the synthesis of one flavone, 5-hydroxy-4′-methoxyflavone.

A series of novel flavone derivatives were designed, synthesized, and evaluated for their H3 R inhibitory activity. The results showed that four compounds exhibited significant anti-H3 R activity. Molecular docking experiments indicated that a salt bridge, hydrogen-bonding, and hydrophobic interactions all contributed to interactions between inhibitors and H3 R.

Flavonoids are widely occurring polyphenols of plant origin and well explored in the field of pharmacological activities. Recent studies showed this scaffold to be more dynamic as fluorescent probe. Very rare reports are there in literature on flavones as liquid crystals, for the first time we have synthesized and characterized flavone and bis-flavone derivatives for mesomorphic properties. Compounds 9a–d and 13a–d were studied for liquid crystalline properties by Differential scanning calorimetry (DSC) and Polarizing optical microscopy (POM) studies. The compounds 8, 9a–d, 12, and 13a–d were also studied for antioxidant property by DPPH assay. We have synthesized new n-alkoxy flavone and Bis-flavone derivatives for liquid crystalline properties. The compounds were characterized by using different spectral techniques, all synthesized compounds did not show mesophase which was confirmed by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM) study. POM image of compound 9c in heating (a) shows direct melting (92.2°C) of compound and cooling (b) goes to crystallization (65.8°C) with no phase. Flavone derivatives are well reported to show broad pharmacological applications, we have also tested compounds for antioxidant properties by DPPH assay.

Seventeen new flavone derivatives substituted at the 4&prime, OH position were designed, synthesized and evaluated for their anticancer and antibacterial activities. Among them, compounds 3, 4, 6f, 6e, 6b, 6c and 6k demonstrated the most potent antiproliferative activities against a human erythroleukemia cell line (HEL) and a prostate cancer cell line (PC3). The results also showed that the IC50 value of compounds 3, 4, 6f, 6e, 6b, 6c and 6k were close to that of the anticancer drug cisplatin (DDP) and lower than that of apigenin. All of the derivatives did not present antibacterial activities. The structure&ndash, activity relationships evaluation showed that the configuration of methyl amino acid might affect their biological activities.

A simple and efficient one pot method has been developed for the synthesis of some new functionalized pyrano fused flavone derivatives, alkyl 4,8-dioxo-2-phenyl-4,8-dihydropyrano[2,3-f]chromene-10-carboxylates and dialkyl 4-oxo-2-phenyl-4,8-dihydropyrano[2,3-f]chromene-8,9-dicarboxylates, from 7-hydroxy flavones and 7-hydroxy 8-formyl flavones using dialkylacetalynedicarboxylates in the presence of triphenyl phosphine. The structures of all synthesized compounds were elucidated by FT-IR, 1H and 13C NMR and Mass spectral analysis.

A highly efficient and selective Pd/C-catalyzed ligand-free cyclocarbonylation reaction for the synthesis of flavones has been developed. Various flavone derivatives were isolated in excellent yields with excellent functional group tolerances. Additionally, catalyst reuse experiments were performed successfully as well.

Synthesis of the benzannulated spiroketal core of the pinnatifinoside family of natural products, via Sonagashira cross-coupling and gold-catalysed spirocyclisation of functionalised flavone derivatives is described. These investigations lay the framework for ongoing synthetic studies towards the pinnatifinoside family, and related biologically active derivatives.

Coumarin and flavone derivatives are highly valuable molecules in drug discovery. Here, two new regioselective cross-dehydrogenation couplings of coumarins and flavones with different ethers via C(sp(3))-H functionalization processes were developed, generating new ether-substituted derivatives not previously reported. These reactions proceeded well via radical mechanisms and provided the corresponding products in good yields.

A series of flavone derivatives conjugated with carbohydrate were synthesized from 2-(3,4-dimethoxyphenyl)-4H-chromen-4-one. The key step is its cross coupling with the carbohydrate under Sonogashira reaction.

Flavones have antioxidant, anti-proliferative, anti-tumor, anti-microbial, estrogenic, acetyl cholinesterase, anti-inflammatory activities and are also used in cancer, cardiovascular disease, neurodegenerative disorders, etc. Also, flavonoids are found to have an effect on several mammalian enzymes like protein kinases that regulate multiple cell signaling pathways and alterations in multiple cellular signaling pathways are frequently found in many diseases. Flavones have been an indispensable anchor for the development of new therapeutic agents. The majority of metabolic diseases are speculated to originate from oxidative stress, and it is therefore significant that recent studies have shown the positive effect of flavones on diseases related to oxidative stress. Due to the wide range of biological activities of flavones, their structure-activity relationships have generated interest among medicinal chemists. The outstanding development of flavones derivatives in diverse diseases in very short span of time proves its magnitude for medicinal chemistry research. The present review gives detail about the structural requirement of flavone derivatives for various pharmacological activities. This information may provide an opportunity to scientists of medicinal chemistry discipline to design selective, optimize as well as poly-functional flavone derivatives for the treatment of multi-factorial diseases.

The formation of methylenebis(chalcone)s has been discovered during deprotection with methoxymethyl groups from trihydroxychalcones. Studies on this methylenation reaction led to a mechanism hypothesis that was extended to other chalcones and to dihydrochalcone, acetophenone, benzophenone and flavone derivatives. This new method was applied to the rapid synthesis of natural product piperanduncin C. These original methylenebis compounds were also evaluated for their antiparasitic activity.

An efficient and practical method for effecting a tandem C-H alkenylation/C-O cyclization has been achieved via the C-H functionalization of flavone derivatives. The synthetic utility of the one-pot sequence was demonstrated by obtaining convenient access to coumarin-annelated benzopyrans. The reaction scope for the transformation was found to be fairly broad, affording good yields of a wide range of flavone- or coumarin-fused benzopyran motifs, which are privileged structures in many biologically active compounds.

A palladium-catalyzed oxidative arylation of chromones was examined. A regioselective 2-arylation of chromone was carried out via a double C–H activation process. The procedure provided an expedient approach for the preparation of flavone derivatives.

The chalcone derivatives, 1-(2′-hydroxyaryl)-3-(2-chloroquinolin-3-yl)-prop-2-en-1-one was transformed to corresponding flavone derivatives by iodine impregnated neutral alumina under microwave irradiation. The synthesized flavone derivatives were structurally confirmed by elemental analysis, UV, IR and1H-NMR spectral data, and the notable yield obtained was compared with previously reported method.

A catalytic amount of DMAP promoted cyclization of o-alkynoylphenols via a 6-endo cyclization mode leading to flavone derivatives in high yields without forming 5-exo cyclized aurone derivatives. Utilizing this method, methoxy substituted flavone and alkyl substituted γ-benzopyranone derivatives were synthesized.

The synthesis of some natural and synthetic biflavonoids was performed in good overall yields starting from readily available materials via high yielding aldol and Ullmann condensations. Some of these compounds, especially bichalcones, display an interesting activity against fungi, higher than that of the corresponding monomers.

Two new acylated flavone C-glycosides, 6''-O-(2'''-methylbutyryl)isoswertisin (1) and 6''-O-(2'''-methylbutyryl)isoswertiajaponin (2), together with four known acylated flavone C-glycosides, were isolated for the first time from the whole plants of Hemistepta lyrata (Compositae). Their structures were elucidated on the basis of chemical and spectroscopic methods including HR-ESI-MS, ESI-MS, UV, IR, and 1D and 2D NMR spectral techniques.

Two new glycosides, 1,6-di-O-syringoyl-β-d-glucopyranose (1) and quercetin 3-O-[(3-O-syringoyl-α-l-rhamnopyranosyl)-(1 → 6)-β-d-glucopyranoside] (2), along with seven known compounds were isolated from the MeOH extract of Leonurus japonicus. The structures of these compounds were elucidated by spectral analysis.

In this paper, a simple and novel synthesis of baicalein is described. This transformation features the novel synthesis of helilandin B and a different way to demethylate. The overall yield of 59% is acceptable.

An expeditious synthesis of three polyoxygenated flavones mosloflavone, negletein and baicalein. starting from crysin, an easily available flavone, by a bromination/methoxylation procedure is reported The convergent synthesis exploits a base induced Wesley-Moser type rearrangement (C) 2009 Elsevier Ltd All rights reserved

High-performance liquid chromatography with diode-array detection has been used to evaluate the quality of Erxian decoction (EXD), a Chinese medicine prescription, by use of a combination of fingerprinting and simultaneous quantification of six marker compounds. The standard chromatographic fingerprint containing forty common peaks was constructed from seven batches of the EXD samples to evaluate batch-to-batch consistency. In addition, six representative bioactive markers were simultaneously quantified with good linearity, precision, repeatability, and accuracy. The fingerprint accompanied by quantification of the marker compounds can be used to evaluate the quality of EXD.

A novel C-glycosylflavone with unusual alpha-orientation at the anomeric center of d-glucose was isolated from the leaves of Diospyros kaki. Its structure was determined as 8-C-[alpha-l-rhamnopyranosyl-(1 --4)]-alpha-d-glucopyranosylapigenin by chemical methods and spectral experiments.

The reliability of evaluation of compound purity depends on the analytical method selected. A suitable analytical method, including the modes of separation and detection, can provide reliable information about compound purity. Effective separation is the key to achieving precise results. In this work we developed a novel method, based on an orthogonal system, RP-LC-hydrophilic interaction liquid chromatography, for evaluating the purity of compounds isolated by preparative reversed-phase liquid chromatography. Because of its good orthogonality, good separation and more accurate assessment of compound purity could be achieved.

A new acylated flavone glycoside, echioidinin 2'-O-beta-D-(2''-O-acetyl)glucopyranoside (1) along with the three known flavonoids, 5,6,7,8,5'-pentamethoxy-3',4'-methylenedioxyflavone (2), 5,2',6'-trihydroxy-7-methoxyflavone (3), and kaempferol 7,4'-dimethyl ether 3-O-beta-D-glucopyranoside (4), were isolated from the roots of Colebrookea oppositifolia. The structure of compound 1 was elucidated by extensive spectral and chemical studies.

Two new steroidal saponins and two known flavonoid glycosides were isolated from the fruits of Tribulus terrestris. Their structures were assigned by spectroscopic analysis and chemical reaction as 26-O-beta-D-glucopyranosyl-(25R)-5 alpha-furostan-12-one-3beta,22 alpha,26-triol-3-O-beta-D-glucopyranosyl (1 --2)-beta-D-glucopyranosyl(1 --4)-beta-D-galactopyranoside (1), 26-O-beta-D-glucopyranosyl-(25S)-5 alpha-furostan-22-methoxy-2 alpha,3beta,26-triol-3-O-beta-D-glucopyranosyl(1 --2)-beta-D-glucopyranosyl(1 --4)-beta-D-galactopyranoside (2), kaempferol-3-gentiobioside (3), and isorhamnetin-3-gentiobioside (4).

Quantitative structure–activity relationship (QSAR) has been established for 32 oxime- and methyloxime-containing flavone and isoflavone derivatives having antiproliferative activity. Multiple linear regressions were used to generate the relationship between biological activity and calculated descriptors. Model with good statistical qualities was developed using the software VLIFE MDS 2.0. Validation of the model was done by cross-validation, randomization, and external test set prediction. On the basis of the QSAR model, we designed a new series of compounds and calculated the activity and found that the compounds were more potent than the existing compounds. QSAR studies of flavone and isoflavone derivatives. The negative coefficient of SdOi indicated that its increase is detrimental to antiproliferative activity. The positive coefficient of QMDMg showed that the magnitude of dipole is responsible for the activity.

A rapid LC-photodiode array method for the separation and identification of secondary plant metabolites especially phenolic compounds belonging to different types in a run (35 min) has been developed. The method has been optimized and validated using the selectivity, precision, recovery and robustness parameters with an aim for standardization of herbal drugs. Almost all the compounds have linearity with an R 2 more than 98% and an RSD of less than 5% (in terms of variation of retention time). Inter-day and intra-day variability was also found to be less than 5%. The method thus developed has been successfully applied in identification and quantification of phenolic compounds present in polyherbal ayurvedic formulation (Ashokarishta). The results indicate that the method developed is rapid, accurate and robust for the analysis of different classes of phenolic compounds and can be successfully applied in the quality control and standardization of herbal drugs as well as polyherbal formulations.

Two new flavonoids, compounds 1 and 2, together with seven known flavonoids, were isolated from Galium verum L. Their structures were elucidated as diosmetin 7-O-alpha-l-rhamnopyranosyl-(1-2)-[beta-d-xylopyranosyl-(1-6)]-beta-d-glucopyranoside (1) and 3,5,7,3',4',3'',5'',7'',3''',4'''-decahydroxyl-[8-CH(2)-8'']-biflavone (2) by chemical methods and spectroscopic analyses. Compounds 3 and 4 were isolated from the genus Galium for the first time.

The synthesis and biological activity of a new series of 2-{3-[substituted benzylamino-methyl)-phenyl]-4H-benzopyrane-4-one (IVa-e) and N-substituted benzyl-N-[3-(4-oxo-4H-benzopyrane-2-yl)benzyl]-3-phenyl-acrylamide (Va-e) derivatives are reported. The synthesized compounds were tested in vitro for antifungal and antibacterial activities. Compound IVa showed the best antifungal activity compared with miconazole (CAS 22916-47-8). Compound IVc indicated the best antibacterial activity compared with the control drug ampicillin (CAS 69-53-4).

A novel flavonoid, [2-(3,4-dihydroxy-phenyl)-3,5,7-trihydroxy-4-oxo-4H-chromen-8-yl]-[8-hydroxy-7-(E-4-hydroxy-3-methyl-but-2-enyl)-2,2-dimethyl-chroman-5-yl]-acetic acid methyl ester (10), trivially named sabian, along with 11 known compounds, have been isolated from the stems and leaves of Sabiayunnanensis. Their structures were established on the basis of spectral analysis.

Dulcinoside (1), dulcisisoflavone (2), dulcisxanthone A (3) and sphaerobioside acetate (6) together with 22 known compounds were isolated from the green fruit of G. dulcis. Dulcisflavan (4), dulcisxanthone B (5) and isonormangostin (7) together with 22 known compounds were isolated from the ripe fruit. Compounds 6 and 7 were synthetic known compounds. Their structures were determined by spectroscopic methods. The radical scavenging and antibacterial activities of some of the compounds were investigated.

Two new flavonosides have been isolated from the roots of Glychirriza glabra and identified as 5,8-dihydroxy-flavone-7-O-beta-D-glucuronide, glychionide A, and 5-hydroxy-8-methoxyl-flavone-7-O-beta-D-glucuronide, glychionide B.

Scutellarin-7-O-glucuronide (1) has been synthesized from 2-hydroxyl-4,5,6-trimethoxyacetophenone through eight steps, including Michael addition, cyclization, hydrogenation, hydroxyl protection, deprotection, etc. The overall yield of 13% is much higher than that reported (0.6%) by L. Farkas, G. Mezey-Vàndor et al. in 1974.

In a chemical investigation on the flavone composition of Leonurus heterophyllus a new flavonoside has been isolated. By means of physico-chemical evidences and spectral analysis its structure has been established as quercetin-3-O-[3-(4-hydroxy-3,5-dimethoxybenzyl)-alpha-L-rhamnopyranosyl]-(1--6)-beta-D-galactopyranoside (1).

The twigs of Dorstenia angusticornis and Dorstenia barteri var. subtriangularis yielded 16 compounds. Two novel diprenylated chalcones: 3,5′-di-(2-hydroxy-3-methylbut-3-enyl)-4,2′,4′-trihydroxychalcone, 3, 4-(2,2-dimethylpyrano)-3′-(2-hydroxy-3-methylbut-3-enyl)-2′,4′-dihydroxychalcone and the known stipulin were isolated from both species. 3-(2-Hydroxy-3-methylbut-3-enyl)-5′-(3,3-dimethylallyl)-4,2′,4′-trihydroxychalcone and the known compounds: 4-hydroxylonchocarpin, kanzonol B, bartericins A, B, C and 3′-(2-hydroxy -3-methylbut-3-enyl)-4,2′,4′-trihydroxychalcone were isolated from D. barteri while the known compounds: gancaonin Q, paratocarpins C, F, and lupeol were obtained from Dorstenia angusticornis . β-Sitosterol and its β- d -glucopyranoside were isolated from both species. Structures of these secondary metabolites were established using spectroscopic analysis, especially, NMR spectra in conjunction with 2D experiments, COSY, HMQC and HMBC.

A new flavonoid was isolated from the whole plant of Spiranthes australis (R. Brown) Lindl (Orchidacea). Its structure was characterized as 3,7-dimethoxy-5-hydroxy-2-([4-(3-methyl-2-butenyl)oxy]phenyl)-4H-1-benzopyran-4-one on the basis of chemical and spectral evidence including 2D NMR analysis.

Six new acylated flavone C-glycosides, 2''-O-(2'''-methylbutyryl)isoswertisin (1), 3''-O-(2'"-methylbutyryl)isoswertisin (2), 2''-O-(2'"-methylbutyryl)vitexin (3), 2''-O-(2'"-methylbutyryl)orientin (4), 2''-O-(3'",4'"-dimethoxybenzoyl)vitexin (5), and 2''-O-(3'",4'"-dimethoxybenzoyl)orientin (6), and the known flavone C-glycoside, isoswertisin, were isolated from the flowers of Trollius ledebouri. The structures of 1-6 were elucidated by spectroscopic methods.

The New Zealand tree Quintinia acutifolia has yielded four biflavonoids, the new 2,3,2'',3''-tetrahydroochnaflavone (3), and its 7,7''-di-O-methyl derivative (1). The rare 7-O-methyl-2,3,2'',3''-tetrahydroochnaflavone (2) and 2'',3''-dihydroochnaflavone (4), both previously identified only from members of the Ochnaceae, were also isolated. Structures were determined by spectroscopic methods. This is the first report of biflavonoids from the Grossulariaceae.

Thalictrum (Ranunculaceae) is an extremely abundant medicinal plant source. Due to their marked ethnopharmacological usages in folk medicine of China and the large number of potentially active chemical constituents, they may be a rich source for new chemicals for drug R&D. Here, an investigation on traditional functions and folk therapeutic uses of Thalictrum plants from China, as well as their main chemical constituents, was undertaken. It showed that 43 Thalictrum plants have long been used as folk medicine to treat many diseases in different races of China. In addition, the correlation between folk therapeutic effects and chemical constituents, and the modern pharmacological activities, are discussed as well as the prospect of isolation and development of new drugs from this genus of plants.

Five new prenylflavonoids, artocommunols CA (1), CB (2), CC (3), CD (4), and CE (5), were isolated from the cortex of the roots of Artocarpus communis, along with the known compound cyclomorusin. The structures of 1-5 were determined by spectral methods.

Ab initio and DFT conformational analysis was performed on the flavone derivatives chrysin (5,7-dihydroxyflavone; 2-phenyl-5,7-dihydroxy-4H-1-benzopyran-4-one) and 7,8-dihydroxyflavone (2-phenyl-7,8-dihydroxy-4H-1-benzopyran-4-one). The structural features required for optimal stabilization in each molecule were identified. It was discovered that sparsely placed hydroxyl groups, particularly with hydrogen bond-like interactions, resulted in lowering the potential energy minimum for the molecules. It was also noted that one of the factors capable of destroying co-planarity was steric interference between closely placed functional groups across the phenyl and the benzo-γ-pyrane ring. Studies performed on the radical forms of the flavonoids, however, showed that the unpaired electron is confined only to the benzo-γ-pyrane ring, and not delocalized across the phenyl ring.Key words: flavonoid, flavone, chrysin, ab initio conformational analysis, anti-oxidant, free radical, 5,7-dihydroxy flavone, 7,8-dihydroxyflavone.

This paper reports the identification of di- and triglycosylated flavonoids from Sorocea bomplandii (Moraceae) by liquid chromatography coupled on-line to nuclear magnetic resonance (LC-NMR). These glycosylated flavonoids may be used as a taxonomic marker in future work.

Various 3-halo flavones were prepared by reaction of the corresponding flavone derivatives with R4NBr/PhI(OAc)2 system under mild reaction conditions.