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Summary: Studies have recently highlighted potential health benefits of young rice leaves; however, optimization of extraction process was often overlooked. The present study aimed to assess impacts of extraction methods, namely, maceration and decoction, on total phenolics content and antioxidant activities based on FRAP, DPPH, and ABTS assays of extracts from Thai cultivar of Jasmine rice leaves. The study examined influences of ethanol concentration (0–100% (v/v) for maceration), boiling time (10–30 min for decoction) and solvent‐to‐solid ratio (20–40 mL g−1 for both maceration and decoction). Results showed that under its optimal condition (50% (v/v) ethanol concentration and solvent‐to‐solid ratio of 30 mL g−1), maceration yielded significantly higher total phenolic content, 12.54 ± 0.94 mg GAE/g DW. Furthermore, mechanisms of single electron transfer responsible for antioxidant activities were explored, identifying flavonoids as potential chemical markers in rice leaf extracts. Flavonoid derivatives, specifically isoorientin (3.33 ± 0.10 mg/g DW) and isovitexin (0.98 ± 0.03 mg/g DW), were subsequently quantified. This research contributed to improved understanding of relations between bioactive compounds and their antioxidant activities. The findings also underscore potential of Thai Jasmine rice leaves as natural additives in future functional foods production. [ABSTRACT FROM AUTHOR]

Chikungunya virus is a re-emerging arbovirus that has caused epidemic outbreaks in recent decades. Patients in older age groups with high viral load and severe immunologic response during acute infection are likely to develop chronic arthritis and severe joint pain. Currently, no antiviral drug is available. Previous studies suggested that a flavone derivative, 8-bromobaicalein, was a potential dengue and Zika replication inhibitor in a cell-based system targeting flaviviral polymerase. Here we characterized that 8-bromobaicalein inhibited chikungunya virus replication with EC50 of 0.49 ± 0.11 µM in Vero cells. The molecular target predicted at viral nsP1 methyltransferase using molecular binding and fragment molecular orbital calculation. Additionally, oral administration of 250 mg/kg twice daily treatment alleviated chikungunya-induced musculoskeletal inflammation and reduced viral load in healthy adult mice. Pharmacokinetic analysis indicated that the 250 mg/kg administration maintained the compound level above EC99.9 for 12 h. Therefore, 8-bromobaicalein should be a potential candidate for further development as a pan-arboviral drug.

Plant virus diseases seriously affect the yield and quality of agricultural products, and their prevention and control are difficult. It is urgent to develop new and efficient antiviral agents. In this work, a series of flavone derivatives containing carboxamide fragments were designed, synthesized, and systematically evaluated for their antiviral activities against tobacco mosaic virus (TMV) on the basis of a structural–diversity–derivation strategy. All the target compounds were characterized by 1H-NMR, 13C-NMR, and HRMS techniques. Most of these derivatives displayed excellent in vivo antiviral activities against TMV, especially 4m (inactivation inhibitory effect, 58%; curative inhibitory effect, 57%; and protection inhibitory effect, 59%), which displayed similar activity to ningnanmycin (inactivation inhibitory effect, 61%; curative inhibitory effect, 57%; and protection inhibitory effect, 58%) at 500 μg mL−1; thus, it emerged as a new lead compound for antiviral research against TMV. Antiviral mechanism research by molecular docking demonstrated that compounds 4m, 5a, and 6b could interact with TMV CP and disturb virus assembly. [ABSTRACT FROM AUTHOR]

Flavonoids are phenolic compounds that have always attracted pharmaceutical researchers and food manufacturers. Nature has indirectly provided us flavones in our daily diet i.e. tea, fruits, juices and vegetables. Flavones have got special position in research field of natural and synthetic organic chemistry due to their biological capabilities. Three substituted flavone derivatives have been synthesized from substituted O-hydroxy acetophenones and 4- trifluoromethyl benzaldehyde in good yield. The structures have been established by different spectroscopic techniques like ¹HNMR 13CNMR, IR spectroscopy. The compounds were then screened for their enzyme inhibition potential and antinociceptive response in mice models with writhings induced by acetic acid, tail immersion and formalin-induced nociception assay procedures and structure activity relationship was established. The effects following pretreatment with naloxone were also studied to reveal the involvement of opioid receptors in the antinociceptive action. The flavone derivatives showed moderate to weak inhibition against LOX. Moreover, significant to moderate decrease in the number of abdominal constrictions, increase in paw-licking response time in both phases and a significant raise in latency time in nociception models. Moreover, the antinociceptive response was significantly attenuated by pretreatment with opioid receptor antagonist suggesting the involvement of opioidergic system in the analgesic action. The flavone derivatives showed analgesic response in all models of nociception suggesting the possible involvement of opioidergic system in the antinociceptive action. [ABSTRACT FROM AUTHOR]

Fluorescent sensors are important tools in environment and life science. Ratiometric fluorescent sensors are more advantageous than single intensity-based ones. Excited-state intramolecular proton transfer (ESIPT) molecules endow dual fluorescence from the excited enol and keto tautomers, providing excellent platforms for constructing ratiometric fluorescent sensors. However, the current ESIPT mechanism for ratiometric fluorescent sensors is relatively simple, resulting in that its application limits in given systems. Therefore, it is essential to construct a ratiometric fluorescent sensor that based on ESIPT molecule with reliable, controlled and general strategy. In this work, we employed a new strategy to construct a ratiometric fluorescent sensor allyl-(4′-methyl-3-hydroxyflavone) carbonate (FA) which is based on the finding that the electron-withdrawing substituted group could nearly block the normal-tautomer tautomerism taking place through excited-stated charge transfer (ESCT). FA exhibited highly selective and ratiometric fluorescent response to Al 3+ and could detect Al 3+ at a low concentration of 0.75 μM in aqueous solution. FA can detect Al 3+ in tap and laker water samples, and in living cells. The proof-of-principle method provides a common strategy for design of ratiometric fluorescent sensors. [ABSTRACT FROM AUTHOR]

A number of 4'-substituted (R = H, Me, Cl, F) flavone derivatives is synthesized from 2-hydroxyacetophenones using the modified Baker-Venkataraman reaction. Compound [3-(4-fluorobenzoyl)-5- hydroxy-4'-fluoroflavone] was synthesized for the first time with the yield of 12%. Antiproliferative assays indicate that the synthesized flavones with F substituent at the 4' position demonstrate higher activity than the other flavone derivatives, particularly against HeLa and MCF-7 with the IC50 9.5 and 2.7 μM, respectively. [ABSTRACT FROM AUTHOR]

Through the orthogonal design of two fluorophores and two recognition groups, a series of fluorescent probes were developed from the flavone derivatives for hydrogen sulfide (H 2 S). The probe FlaN-DN stood out from the primarily screening on the selectivity and response intensities. Among the recent reported probes for the H 2 S detection, FlaN-DN indicated the most highlighted advantages including the rapid response (within 200 s) and the high response multiplication (over 100 folds). Moreover, FlaN-DN suggested practical capabilities including a wide linear range (0–400 μM), a relatively high sensitivity (limit of detection 0.13 μM), and high selectivity towards H 2 S. As a low cytotoxic probe, FlaN-DN achieved the imaging in living HeLa cells. FlaN-DN could detect the endogenous generation H 2 S and visualize the dose-dependent responses to the exogenous H 2 S level. [Display omitted] • A series of fluorescent probes for hydrogen sulfide developed from flavone derivatives. • Highlighted advantages including the rapid response within 200 s and the high response multiplication. • Practical capabilities including a wide linear range, a relatively high sensitivity, and high selectivity. • Achieveing the imaging of endogenous generation and exogenous H 2 S in living HeLa cells. In this work, through the orthogonal design of two fluorophores and two recognition groups, a series of fluorescent probes were developed from the flavone derivatives for hydrogen sulfide (H 2 S). The probe FlaN-DN stood out from the primarily screening on the selectivity and response intensities. It could respond to H 2 S with both the chromogenic and fluorescent signals. Among the recent reported probes for the H 2 S detection, FlaN-DN indicated the most highlighted advantages including the rapid response (within 200 s) and the high response multiplication (over 100 folds). FlaN-DN was sensitive to the pH condition, thus could be applied to distinguish the cancer micro-environment. Moreover, FlaN-DN suggested practical capabilities including a wide linear range (0–400 μM), a relatively high sensitivity (limit of detection 0.13 μM), and high selectivity towards H 2 S. As a low cytotoxic probe, FlaN-DN achieved the imaging in living HeLa cells. FlaN-DN could detect the endogenous generation H 2 S and visualize the dose-dependent responses to the exogenous H 2 S level. This work provided a typical case of natural-sourced derivatives as functional implements, which might inspire the future investigations. [ABSTRACT FROM AUTHOR]

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 KCO (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. [ABSTRACT FROM AUTHOR]

Flavonoids are phenolic compounds that have always attracted pharmaceutical researchers and food manufacturers. Nature has indirectly provided us flavones in our daily diet i.e. tea, fruits, juices and vegetables. Flavones have got special position in research field of natural and synthetic organic chemistry due to their biological capabilities. Flavone derivative has been synthesized in good yield from ketone and corresponding aldehydes. The structures have been established by different spectroscopic techniques like 1H NMR, 13C NMR, IR and elemental analysis. The compounds were then screened for its acute toxicity and antinociceptive response in mice models with writhings induced by acetic acid, tail immersion and formalin-induced nociception assay procedures and structure activity relationship was established. The compounds were safe up to a maximum dose of 1200 mg/kg body weight in mice. The effects following pretreatment with naloxone were also studied to reveal the involvement of opioid receptors in the antinociceptive action. The flavone derivatives showed significant reduction in number of abdominal constrictions, increase in paw licking response time in both phases and a significant raise in latency time in nociception models. Moreover, the antinociceptive response was significantly attenuated by pretreatment with naloxone suggesting the involvement of opioid system in the antinociceptive action. The promising effects were shown by halogenated flavone. The flavone derivatives showed analgesic response in all models of nociception suggesting the involvement of opioid system in the antinociceptive action. [ABSTRACT FROM AUTHOR]

Three new flavone derivatives, paranicflavones A–C ( 1 – 3 ), together with three known similar compounds ( 4 – 6 ), were isolated from their roots and stems of Tiandeng tobacco. Their structures were elucidated by spectroscopic methods, including extensive 1 H and 13 C NMR techniques. Additionally, compounds 1 – 6 were evaluated for their anti-tobacco mosaic virus (anti-TMV) activities, and compound 2 exhibited anti-TMV activity with inhibition rate of 35.8%, which is higher than that of positive control, ningnanmycin. [ABSTRACT FROM AUTHOR]

A series of flavonyl-2,4-thiazolidinedione, imidazolidinedione and rhodanine derivatives were tested for their antioxidant activity as scavengers of oxygen free radicals. Free radical scavenging activities, including superoxide anion radical (O•2), hydroxyl radical (HO•) and 2,2'-diphenyl-1-picrylhydrazyl free radical have been evaluated using chemiluminescence, electron paramagnetic resonance and spin trapping with 5,5-dimethyl-1-pyrroline-1-oxide as a spin trap. Potassium superoxide in dimethylsulfoxide and 18-crown-6 ether were used for the production of O•2. Hydroxyl radical was generated using the Fenton reaction. Ten of the eleven examined compounds exhibited decrease in chemiluminescence, but there were large differences in the decrease, ranging from 16% to 89%; also, two of these compounds increased light emission by about 200%. On the contrary, all compounds tested exhibited 30-68% scavenging HO• and 25-96% scavenging the DPPH• radical respectively. Possible mechanisms are proposed to explain the results. [ABSTRACT FROM AUTHOR]

Abstract: Based on molecular docking analysis of complexes between flavone and the c-myc G-quadruplex, we designed and screened 30 flavone derivatives containing various side chains that could potentially form interactions with the G-quadruplex grooves. As a proof-of-concept, the highest-scoring flavone derivatives containing cationic pyridinium side chains were synthesized and their interactions with the c-myc G-quadruplex were examined using a PCR-stop assay. The stabilizing effects of the flavone derivatives were found to be selective towards the c-myc G-quadruplex over other biologically relevant G-quadruplex structures, such as the human telomeric sequence (HTS). The interaction between the most potent compound of the series and the c-myc G-quadruplex was examined in depth using UV–Vis titration, molecular modeling and CD spectroscopy. Our results suggest that in addition to stabilizing the c-myc G-quadruplex, the flavone derivatives were capable of inducing the formation of the G-quadruplex structure even in the absence of monovalent cations. The flavone derivatives were found to be potent inhibitors of c-myc promoters within the cellular environment and displayed promising cytotoxic behavior against human cancer cell lines. [Copyright &y& Elsevier]

Abstract: Although several flavonoids have been reported to exert inhibitory effects on influenza H1N1 neuraminidase (NA), little is known about the structure–activity relationship and binding mode. Three dimensional QSAR (quantitative structure–activity relationship) and molecular docking approaches were applied to explore the structural requisites of flavone derivatives for NA inhibitory activity. A meaningful QSAR model with R 2 of 0.5968, Q 2 of 0.6457, and Pearson-R value of 0.8679, was constructed. From the QSAR model, it could be seen how 6-OH, 3′-OH, 4′-OH, and 8-position substituent affect the NA inhibitory activity. Molecular docking study between the most active compound and NA suggested that hydrogen bonds, hydrophobic and electrostatic interactions were closely related to NA inhibitory activity, 5-OH and 7-OH may be essential for this activity. The results provide a set of useful guidelines for the rational design of novel NA inhibitors. [Copyright &y& Elsevier]

Abstract: The K ds (dissociation constants) of 21 flavone derivatives have been obtained by fluorescence in vitro when binding with Aβ(1–40) (β-amyloid(1–40)) aggregates protein. Extensive 3D-QSAR (quantitative structure–activity relationship) studies were performed on the fluorescent flavones, which are excellent ligands of Aβ(1–40) aggregates protein. Comparative molecular similarity indices analysis (CoMSIA) technique was used to relate the binding affinities with the ligand structures, and the QSAR model was obtained using the CoMFA technique. The QSAR model was proved to statistically significant and have high predictive power: the CoMSIA model yielded the cross-validated q 2 =0.512 and the non-cross-validated r 2 =0.911. This model showed that electrostatic (22.5%) and H-bond interaction (acceptor 15.3%; donor 45.1%) properties played major roles in ligand binding process. The QSAR model was further graphically interpreted in terms of field contribution maps. In order to further investigate the specific binding site of the flavones in the Aβ(1–40) aggregates, preliminary docking studies were performed. According to the 3D-QSAR results, the possible binding site in the protein was proposed in order to direct the molecular docking studies. A good correlation (R 2: 0.846) between the calculated binding energies and the experimental binding affinities (pK ds) suggests that the identified binding site is reliable. The 3D-QSAR model and the information of the ligand–protein interaction will be helpful in the selection of flavones to be structurally modified and labeled by a radio nuclide for imaging Aβ(1–40) aggregates in the AD (Alzheimer''s disease) brain. [Copyright &y& Elsevier]

Abstract: The present work deals with the chemometric modeling of antioxidant molecules belonging to the class of flavone derivatives employing the quantitative structure–activity relationship (QSAR) technique. A QSAR model was initially built based on the Fujita–Ban method with the training set molecules. Due to the inability of the Fujita–Ban type model to predict satisfactorily the activity of the test set molecules, further QSAR models were built using different chemometric tools (genetic function approximation, genetic partial least squares) with additional descriptors viz., topological, structural, spatial and quantum chemical ones. The statistically significant models thus developed suggest that hydroxy and methoxy substituents at certain specified positions of the A and B rings of the flavone moiety chiefly influence the antioxidant activity of these molecules. [ABSTRACT FROM AUTHOR]

Abstract: Natural flavonoids have broad biological activity, including anticancer. In this study, a series of novel flavone derivatives were synthesized with the substitutions of chlorine, isopropyl, methoxy, and nitro groups on the benzene ring of flavone skeleton to develop effective anticancer agents. Antiproliferative assays showed that the synthesized chemicals possess notable activity against hepatocarcinoma cells (HepG-2); in particular, the compound 6f with chlorine and dimethoxy modifications at the two benzene rings showed an IC50 at 1.1μM to HepG-2. The 6f also displayed marked anticancer activity towards a panel of cancer cells, including nasopharyngeal carcinoma cells (CNE-2 and CNE-1), breast adenocarcinoma cell (MCF-7), and epithelial carcinoma cells (Hela). Exposing HepG-2 cells to compound 6f at 10μM induced chromatin condensation, nuclear disassembly, and DNA fragmentation. In 6f-treated HepG-2 cells, the sub-G0 population was remarkably increased; and in these cells, both caspase-8 and caspase-9 activity was significantly increased, which in turn activated caspase-3. In addition, proapoptotic Bax was upregulated by compound 6f while the antiapoptotic Bcl-2 was downregulated. Taken together, our data suggest that the new flavonoid derivative 6f triggers apoptosis through both death-receptor and mitochondria-dependent intrinsic pathways, being a potent therapeutic agent against hepatocarcinoma. [ABSTRACT FROM AUTHOR]

Abstract: We establish useful models that relate experimentally measured biological activities of compounds to their molecular structure. The pED 50 feeding inhibition on Spodoptera litura species exhibited by aurones, chromones, 3-coumarones and flavones is analyzed in this work through the hypothesis encompassed in the Quantitative Structure–Activity Relationships (QSAR) Theory. This constitutes a first necessary computationally based step during the design of more bio-friendly repellents that could lead to insights for improving the insecticidal activities of the investigated compounds. After optimizing the molecular structure of each furane and pyrane benzoderivative with the semiempirical molecular orbitals method PM3, more than a thousand of constitutional, topological, geometrical and electronic descriptors are calculated and multiparametric linear regression models are established on the antifeedant potencies. The feature selection method employed in this study is the Replacement Method, which has proven to be successful in previous analyzes. We establish the QSAR both for the complete molecular set of compounds and also for each chemical class, so that acceptably describing the variation of the inhibitory activities from the knowledge of their structure and thus achieving useful predictive results. The main interest of developing trustful QSAR models is that these enable the prediction of compounds having no experimentally measured activities for any reason. Therefore, the structure–activity relationships are further employed for investigating the antifeedant activity on previously synthesized 2-,7-substituted benzopyranes, which do not pose any measured values on the biological expression. One of them, 2-(α-naphtyl)-4H-1-benzopyran-4-one, results in a promising structure to be experimentally analyzed as it has predicted pED 50 =1.162. [Copyright &y& Elsevier]

Aldose reductase (AR) is implicated to play a critical role in diabetes and cardiovascular complications because of the reaction it catalyzes. AR enzyme appears to be the key factor in the reduction of glucose to sorbitol. Synthesis and accumulation of sorbitol in cells due to AR activity is the main cause of diabetic complications, such as diabetic cataract, retinopathy, neuropathy and nephropathy. Aldose reductase inhibitors have been found to prevent sorbitol accumulation in tissues. Numerous compounds have been prepared in order to improve the pharmacological prophile of inhibition of aldose reductase enzyme. In this study, seventeen flavonyl-2,4-thiazolidinediones (flavonyl-2,4-TZD) (Ia-e, IIa-e and IIIa-g) were tested for their ability to inhibit rat kidney AR. Compound Ib showed the highest inhibitory activity (88.69 ± 1.46%) whereas Ia, IIa, IIIa, IIIb also showed significant inhibitory activity (49.26 ± 2.85, 67.29 ± 1.09, 71.11 ± 1.95, 64.86 ± 1.21%, respectively). [ABSTRACT FROM AUTHOR]

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). [ABSTRACT FROM AUTHOR]

Abstract: Isolation and biological characterization of pure compounds was used to identify and characterize estrogenic activity and estrogen receptors (ER) preference in chemical components of Achillea millefolium. This medicinal plant is used in folk medicine as an emmenagogue. In vitro assay, based on recombinant MCF-7 cells, showed estrogenic activity in a crude extract of the aerial parts of A. millefolium. After fractionation of the crude extract with increasing polar solvents, estrogenic activity was found in the methanol/water fraction. Nine compounds were isolated and characterized by HR-MS spectra and 1D- and 2D-NMR techniques. In particular, dihydrodehydrodiconiferyl alcohol 9-O-β-d-glucopyranoside – a glycosyl-neolignan – was isolated for the first time from the genus Achillea in addition to six flavone derivatives, apigenin, apigenin-7-O-β-d-glucopyranoside, luteolin, luteolin-7-O-β-d-glucopyranoside, luteolin-4′-O-β-d-glucopyranoside, rutin, and two caffeic acid derivatives, 3,5-dicaffeoylquinic acid and chlorogenic acid. Apigenin and luteolin, the most important estrogenic compounds among those tested, were studied for their ability to activate α or β estrogen receptors (ERα, ERβ) using transiently transfected cells. Our results suggest that isolation and biological characterization of estrogenic compounds in traditionally used medicinal plants could be a first step in better assessing further (e.g. in vivo) tests of nutraceutical and pharmacological strategies based on phytoestrogens. [Copyright &y& Elsevier]

Abstract: In this paper, novel capillary electrophoresis (CE) methods, which used ionic liquids (1-ethyl-3-methylimidazoium tetrafluoroborate, 1-butyl-3-methylimidazoium tetrafluoroborate), were established to separate and determine some bioactive flavone derivatives in Chinese herb Seriphidium santolinum (Schrenk) Poljak. In order to investigate the traits of ionic liquids in CE, borate was also used as electrolyte to compare with. And the excellence of CE, which used ionic liquids as main running electrolyte and β-cyclodextrin (β-CD) as modifier, was illuminated as well. As a result of the study, the difference of ionic liquids and borate in CE was discussed and the advantage of CE, which used ionic liquids as electrolytes for separation, was shown. The analysis was obtained within short time (5–6min). From the result, it was found that the system, which used ionic liquids, was robust because the joule heating was small. The method of CE, which used ionic liquids, has lower detection limits (0.137–0.642μg/mL) than that of borate (0.762–1.036μg/mL). And the CE, which used ionic liquids method, has lower limit of linear range (1.100–2.656μg/mL), while that of CE, which used borate method, was 2.188–5.313μg/mL. [Copyright &y& Elsevier]

Abstract: The antiproliferative activity of several flavonoids isolated from Linaria reflexa Desf. (Scrophulariaceae) was evaluated in vitro by the SRB assay against the large cell lung carcinoma cell line COR-L23, hepatocellular carcinoma cell line HepG-2, renal adenocarcinoma cell line ACHN, amelanotic melanoma cell line C32, colorectal adenocarcinoma cell line Caco-2, and normal human fetal lung MRC5. Chemical modifications, that is acetylation, hydrolysis of rutinose unit, and hydrolysis of the terminal rhamnose unit, were performed on pectolinarin. Pectolinarin exhibited strong cytotoxic activity on COR-L23, Caco-2, and C32 cell lines with an IC50 of 5.03, 6.18, and 7.17μM. Similar activities were recorded for the three natural monoacetyl pectolinarin derivatives linariin, isolinariin A, and isolinariin B. In contrast, peracetylpectolinarin displayed only marginal activity. [Copyright &y& Elsevier]

A new series of flavonyl pro-drug esters of ampicillin (Va-b) was prepared by condensing the appropriate bromomethyl flavone with ampicillin trihydrate potassium salt. Flavone derivatives and ampicillin both have good antibacterial activity. The synthesized compounds were tested for their antifungal and antibacterial activities in vitro. Both of the compounds were active against Candida krusei and Staphylococcus aureus. [ABSTRACT FROM AUTHOR]

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The reactions of iodoflavone with 3-methyl-3-hydroxybut-1-yne and 3-methylbut-3-en-2-yne are described and the antimicrobial and cytotoxic activities of the obtained compounds have been tested. The molecular structures of 6-(3-hydroxy-3-methylbut-1-ynyl)-flavone (1a) and 6-(3-methylbut-3-en-1-ynyl) flavone (1b) have been determined by X-ray crystallography. The planar configuration of the two compounds has been attributed to intramolecular hydrogen bond interactions. In 1a, the presence of the hydroxyl group determines a dimeric arrangement of the molecules. In both compounds in the crystal state, molecular stacking has been observed. [Copyright &y& Elsevier]