Flavanone Skeleton Research Articles

Molecular Structure, Antioxidant Potential, and Pharmacokinetic Properties of Plant Flavonoid Blumeatin and Investigating Its Inhibition Mechanism on Xanthine Oxidase for Hyperuricemia by Molecular Modeling.

Hyperuricemia, which usually results in metabolic syndrome symptoms, is increasing rapidly all over the world and becoming a global public health issue. Xanthine oxidase (XO) is regarded as a key drug target for the treatment of this disease. Therefore, finding natural, nontoxic, and highly active XO inhibitors is quite important. To get insights into inhibitory potential toward XO and determine antioxidant action mechanism depending on the molecular structure, plant flavonoid blumeatin was investigated for the first time by Fourier transform infrared (FTIR) spectroscopy, density functional theory (DFT), ADME/Tox (absorption, distribution, metabolism, excretion, and toxicity) analysis, and molecular docking study. Theoretical findings indicated that blumeatin has high radical scavenging activity due to its noncoplanarity and over twisted torsion angle (-94.64°) with respect to its flavanone skeleton could explain that there might be a correlation between antioxidant activity and planarity of blumeatin. Based on the ADME/Tox analysis, it is determined that blumeatin has a high absorption profile in the human intestine (81.93%), and this plant flavonoid is not carcinogenic or mutagenic. A molecular docking study showed that Thr1010, Val1011, Phe914, and Ala1078 are the main amino acid residues participating in XO's interaction with blumeatin via hydrogen bonds.

Aromatase inhibitors isolated from a flowering tea, snow Chrysanthemum (the capitula of Coreopsis tinctoria Nutt.).

Methanol extract from the capitula of Coreopsis tinctoria Nutt. (Asteraceae), which is also known as a flowering tea or blooming tea "Snow Chrysanthemum," was found to inhibit the enzymatic activity of aromatase. A total of 24 known isolates (1-24) were identified from the extract, including three chalcones (1-3), an aurone (4), five flavanones (5-9), four flavanols (10-13), a flavonol (14), and two biflavanones (15, 16). Among them, okanin (1, Ki = 1.6μM), (2S)-naringenin (5, 0.90μM), isookanin (6, 0.81μM), (2S)-7,3',5'-trihydroxyflavaone (7, 0.13μM), and (2S)-5,7,3',5'-tetrahydroxyflavanone (8, 0.32μM) exhibited relatively potent competitive inhibition. Specifically, the isolates 7 and 8, having a common 3',5'-resorcinol moiety at the B ring in their flavanone skeleton, exhibited potent inhibitory activities compared to those of a clinically applied aminoglutethimide (0.84μM) and naturally occurring flavone, chrysin (0.23μM), which is a common non-steroidal aromatase inhibitor. Importantly, the active flavonoid constituents (1 and 5-8) did not inhibit the activity of 5α-reductase enzyme, which normally reacts with the same substrate "testosterone," thus, these compounds were suggested to be specific to aromatase.

Albumin-catalysed synthesis of flavanones

Flavanones are a family of phytochemicals that have regained importance over the last decade due to their diverse biological activity. The conventional building of the flavanone skeleton is accomplished through a Claisen-Schmidt condensation followed by an intramolecular oxa-Michael addition, but the involved strong basic pH favours side reactions and affects flavanone yield. This work presents a mild access to flavanones based on a sustainable catalyst, bovine serum albumin (BSA), which is a promiscuous protein. BSA catalysed the reaction between a set of 2 ´ -hydroxyacetophenones and benzaldehydes in methanol at 60 °C to give the corresponding flavanones in 58–90% conversions. Experiments showed that BSA promotes the Claisen-Schmidt step as well as accelerates the subsequent oxa-Michael addition. Besides, BSA-catalysed reaction of acetophenone and benzaldehyde was studied, which afforded the Michael adduct 1,3,5-triphenylpentane-1,5-dione (85% conversion). On the whole, the herein reported results expand the potential of BSA as a mild and sustainable catalyst in organic synthesis.

Conformational analysis and reactivity of naringenin

The citrus naringenin (NAR) is a bioactive flavanone that represents an important platform for the development of new drugs. Bioavailability is a limiting factor to proceed with clinical studies and the insertion of lipophilic groups to the flavanone skeleton is a strategy for improving the biological response. However, side reactions, such as ring-opening isomerization of the pyranone ring, often compromise the efficiency of the reaction. Here, we discuss the NAR reactivity, evaluating the chemo- and regioselective conditions, and the factors that lead to ring-opening isomerization. The mechanistic studies were performed by density functional theory (DFT), thermodynamic properties and real-time 1H and 13C NMR monitoring. In addition, we explore the conformational space of NAR through molecular dynamics (MD) simulation. Mechanistic studies of flavanone isomerization, as well as thermodynamic properties, have not yet been reported in the literature.

A new homoisoflavan from Dracaena cinnabari Balf. f. resin: α-glucosidase and COX-II inhibitory activity

A new homoisoflavan, identified as (3 R)-7-hydroxy-3′,4′-methylenedioxyhomoisoflavan, was isolated from Dracaena cinnabari Balf. f. resin. The structure was elucidated by one- and two-dimensional NMR spectroscopy as well as high resolution mass spectrometry. In addition, a diverse group of flavonoids were isolated, representing homoisoflavans, flavans, flavanones, chalcones and dihydrochalcones. The compounds were evaluated for their α-glucosidase and COX-II inhibition activity. The obtained IC50 values of the tested flavonoids gave an insight about some key structural features to their α-glucosidase and COX-II inhibitory activity. For α-glucosidase inhibitory activity, a flavanone skeleton was favorable over a flavan. For COX-II inhibition, the introduction of a fused heterocyclic ring at the homoisoflavan skeleton enhanced the activity.

Panduratins Q–Y, dimeric metabolites from Boesenbergia rotunda and their antiausterity activities against the PANC-1 human pancreatic cancer cell line

A methanolic extract of the rhizomes of Boesenbergia rotunda showed potent preferential cytotoxicity against PANC-1 human pancreatic cancer cells under nutrient deficiency conditions with a PC50 value of 6.6 μg/mL. Bioactivity-guided phytochemical investigation of the rhizomes of B. rotunda led to the isolation of nine undescribed dimeric metabolites, panduratins Q–Y. Their structures were elucidated based on NMR, MS, and ECD spectroscopic data interpretation. Panduratins Q–S and U–W exhibited potent cytotoxicity towards PANC-1 cell line with the PC50 values ranging from 0.8 to 6.3 μM. Panduratin W, which possessed a cyclohexenylchalcone-linked flavanone skeleton, showed the most cytotoxicity with a PC50 value of 0.8 μM under nutrient-deprived medium.

An effective integrated method for comprehensive identification of eighty-five compounds in Zhi-Zi-Da-Huang decoction by HPLC-DAD-ESI-MS (TOF) and HPLC-DAD-ESI-MS/MS (QqQ) without the help of reference standards

Zhi-Zi-Da-Huang decoction (ZZDHD) is an effective formula to treat alcoholic liver disease in China for nearly 2000 years. However, compounds in the formula are still not clear due to the complexity of the coexisting constituents. In this study, a sensitive integrated method based on HPLC-DAD-ESI-MS (TOF) and HPLC-DAD-ESI-MS/MS (QqQ) was developed and 85 chemical compounds in ZZDHD were identified. By TOF/MS, the quasi-molecular ions of the constituents were deduced according to the accurate mass of corresponding positive and negative ions, and product ion scan was then carried out using QqQ/MS. The fragments of each compound were observed by TOF/MS and/or QqQ/MS. Compounds with different chemical structures and concentration levels were tentatively identified according to their chromatographic retention time, UV absorption and MS data. Fragmentation patterns of six types were proposed to verify the identification results. It was found that at TOF/MS mode, a retro diels-alder (RDA) reaction occurred at bonds 1 and 3 in C-ring of flavanone 7-O-diglycosides when 4′-OH exists at B-ring. While the reaction was not observed if a methoxyl group appeared at the same site of flavanone skeleton. Another important phenomenon was noticed that 3-sinapoyl-5-caffeoylquinic acid, 4-sinapoyl-3-caffeoylquinic acid, and sinapylglucoside were detected only in ZZDHD while they were not found in four component herb extracts. The phenomenon revealed that changes of compounds happened when the component herbs were decocted together. The results in the paper are favorable of the clinic dosage and have laid a foundation for the subsequent research of ZZDHD in vivo.

NMR metabolomics for identification of adenosine A1 receptor binding compounds from Boesenbergia rotunda rhizomes extract

Ethnopharmacological relevanceBoesenbergia rotunda Linn. (Zingiberaceae) is traditionally used in many Asian countries as medicine for stomach pain and discomfort, viral and bacterial infection, inflammation, and as diuretic agent. Aim of the studyThe study aimed to identify adenosine A1 receptor binding compounds from Boesenbergia rotunda rhizome extract by using comprehensive extraction coupled to the NMR metabolomics method. Materials and methodsDried and powdered Boesenbergia rotunda rhizomes were extracted with the comprehensive extraction method to obtain several fractions with different polarity. Each fraction was divided into two: for NMR analysis and for adenosine A1 receptor binding test. Orthogonal projection to the least square analysis (OPLS) was used to study the correlation between metabolites profile and adenosine A1 receptor binding activity of the plant extracts. Based on Y-related coefficient and variable of important (VIP) value, signals in active area of OPLS loading plot were studied and the respective compounds were then elucidated Results and discussionsBased on OPLS Y-related coefficient plot and variable of importance value plot, several characteristic signals were found to positively correlate to the binding activity. By using 1D and 2D NMR spectra of one of the most active fraction, pinocembrine and hydroxy-panduratin were identified as the possible active compounds. Two signals from ring C of pinocembrine flavanone skeleton with negative coefficient correlations possibly overlapped with those of non-active methoxylated flavanones which were also presence in the extract. NMR based metabolomics applied in this study was able to quickly identify bioactive compounds from plant extract without necessity to purify them. Further confirmation by isolating pinocembrine and hydroxy-panduratin and testing their adenosine A1 receptor binding activity to chemically validate the method are required. ConclusionTwo flavonoid derivatives, pinocembrine and hydroxy-panduratin, have been elucidated as possible active compounds bind to adenosine A1 receptor. Flavonoid was reported to be one of natural antagonist ligand for adenosine A1 receptor while antagonistic activity to the receptor is known to associate with diuretic activity. Thus, the result of this research supports the traditional use of Boesenbergia rotunda rhizome extract as diuretic agent.

NMR investigation of a novel excipient, α‐glucosylhesperidin, as a suitable solubilizing agent for poorly water‐soluble drugs

α-Glucosylhesperidin (Hsp-G), a functional food additive, significantly enhances the solubility and bioavailability of poorly water-soluble drugs despite little surface activity. Herein, we present investigations into the underlying mechanism by nuclear magnetic resonance techniques. A concentration dependence of the chemical shift of Hsp-G protons correlated well with a mass-action law model, indicating self-association of Hsp-G molecules. The critical micelle concentration was 5.0 mg/mL (6.5 mM) at 37°C. The gradual rather than abrupt chemical shift variation upon Hsp-G aggregation would be different mode to conventional surfactants. Dynamic light scattering and two-dimensional nuclear Overhauser effect spectroscopy measurements demonstrated that Hsp-G molecules self-associated into particular small micelles, with the flavanone skeleton forming a hydrophobic core, and surrounding sugar groups working as a shell. The packing of the hydrophobic portion is not strictly oriented and the intermolecular arrangement of micelle shell is loose. Solubility enhancement was due to the incorporation of drugs into Hsp-G micelle, with naringenin being more soluble than flurbiprofen. This difference is possibly related to the structural similarities between the hydrophobic portion and the micelle core. Hsp-G micellization process with little loss of surface tension is a unique observation in surface and interface science. © 2011 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 100:4421–4431, 2011

Cytotoxic Activities of Several Geranyl-Substituted Flavanones

Nine geranylated flavanones isolated from the fruits of Paulownia tomentosa (4-12) and two from the roots of Morus alba (13 and 14) were examined for cytotoxicity to selected human cancer cell lines and normal human fibroblasts. Cytotoxicity was determined in vitro using a calcein AM cytotoxicity assay. Cytotoxicity for the THP-1 monocytic leukemia cell line was tested using erythrosin B cell staining. The geranylated compounds tested were compared with the known simple flavanone standards taxifolin (1), naringenin (2), and hesperetin (3) and with the standard anticancer drugs olomoucine II, diaziquone, and oxaliplatin and the antineoplastic compound camptothecin, and showed different levels of cytotoxicity. The effects of structural changes on cytotoxic activity, including geranyl substitution of the flavanone skeleton and the oxidation pattern of ring B of the flavanones, are discussed.

Cytotoxic Activity ofC-Geranyl Compounds fromPaulownia tomentosaFruits

The newly discovered 5,7-dihydroxy-6-geranylchromone ( 1) was isolated from PAULOWNIA TOMENTOSA fruit and subsequently characterized. The structure of the isolated compound was elucidated on the basis of extensive NMR experiments including HMQC, HMBC, COSY, and NOESY, as well as HR-MS, IR, and UV. The cytotoxicity of 1 was evaluated using a plant cell model represented by tobacco BY-2 cells. The other phytoconstituents ( 2 - 8) previously isolated from P. TOMENTOSA were similarly evaluated together with the known flavanones 10 and 11. The cytotoxicity (human erythro-leukaemia cell line K562) and activity on erythroid differentiation of compounds 2 - 9 and 12 and 13 have also been evaluated. Acteoside ( 2) was determined to be the most toxic of the compounds tested on BY-2 cells, diplacone ( 6) on the K562 cell line. Some aspects of the relationship between the flavanone skeleton substitution and the metabolic activation necessary for a toxic effect are discussed.

New 7,8-benzoflavanones as potent aromatase inhibitors: Synthesis and biological evaluation

Some natural compounds such as flavonoids are known to possess a moderate inhibitory activity against aromatase, this enzyme being an interesting target for hormone-dependent breast cancer treatment. It has been demonstrated that the modulation of flavonoid skeleton could increase anti-aromatase effect. Therefore, new 7,8-benzoflavanones were synthesized and tested for their activity toward aromatase inhibition. It was observed that the introduction of a benzo ring at position C-7 and C-8 on flavanone skeleton led to new potent aromatase inhibitors, the resulting 7,8-benzoflavanones being until nine times more potent than aminogluthetimide (the first aromatase inhibitor used clinically).

Separation mechanism and determination of flavanones with capillary electrophoresis and high-performance liquid chromatography

To probe separation mechanism and determination with capillary zone electrophoresis (CZE) and liquid chromatography (LC), nine compounds with identical flavanone skeleton were studied. Optimum separation of LC was attained with gradient of acetonitrile and 5 mM phosphate buffer (pH 6.9). For CE, electrolyte buffer was 4.5 mM SDS in 32 mM sodium tetraborate buffer (pH 9.2). The distinguishing feature in this work was successful separation of monohydroxyl stereoisomers by CZE. Polarity is generally increased with hydroxyl groups. In a separation mechanism study, polarity would be reduced by intramolecular hydrogen bond between hydroxyl of C5 and carbonyl group of C4. Comparison of the retention results among monohydroxyl flavanones shows polarity with hydroxyl at C6 the least, and that at C4′ and C7 nearly equal. Also, elution order of flavones and flavanones would be adverse due to the hydroxyl at C3 in LC. From the numerical value p K a of flavanone, the C7-OH is the smallest, and two hydroxyl groups in an adjacent position is always less than the unique one caused by forming a stable 5-membered ring. Investigation of separation mechanism yield only the effect of constituent but also reasonable explanation for contradictory results between Wulf and our laboratory, this due to the hydroxyl at C3.

Spasmolytic Flavonoids from Syzygium samarangense (Blume) Merr. & L.M. Perry

The hexane extract of Syzygium samarangense (Ss.Hex) dose-dependently (10-1000 microg/ ml) relaxed the spontaneously contracting isolated rabbit jejunum. Four rare C-methylated flavonoids with a chalcone and a flavanone skeleton were isolated from Ss.Hex and were subsequently tested for spasmolytic activity. All flavonoids, identified as 2'-hydroxy-4',6'-dimethoxy-3'-methylchalcone (1), 2',4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone (2), 2',4'-dihydroxy-6'-methoxy-3'-methylchalcone (3), and 7-hydroxy-5-methoxy-6,8-dimethyl-flavanone (4), showed dose-dependent spasmolytic activity in the rabbit jejunum with IC50 values of 148.3 +/- 69.4, 77.2 +/- 43.5, 142.4 +/- 58.6 and 178.5 +/- 37.5 microg/ml (mean +/- SEM), respectively. The dihydrochalcone derivative of compound 1, 2'-hydroxy-4',6'-dimethoxy-3'-methyldihydrochalcone (5), when tested for spasmolytic activity, did not significantly relax the smooth muscle relative to the other compounds. Verapamil, a standard spasmolytic, has an IC50 value of 0.16 +/- 0.04 microg/ml. This is the first report of the relaxant activity of chalcones, specifically of compounds 1-3.

Metabolism of 8-prenylnaringenin, a potent phytoestrogen from hops (Humulus lupulus), by human liver microsomes.

The female flowers of hops are used throughout the world as a flavoring agent for beer. Recently, there has been increasing interest in the potential estrogenic properties of hop extracts. Among the possible estrogenic compounds in hops, 8-prenylnaringenin is perhaps most significant due to its high in vitro potency exceeding that of other known phytoestrogens. Since data regarding the pharmacokinetic properties of this compound are lacking, we investigated the in vitro metabolism of 8-prenylnaringenin by human liver microsomes. A total of 12 metabolites were identified, and biotransformation occurred on the prenyl group and the flavanone skeleton. The major site of oxidation was on the terminal methyl groups, and of the two possible isomers, the transisomer was more abundant. The double bond on the prenyl group was also oxidized to an epoxide that was opened by intramolecular reaction with the neighboring hydroxyl group. On the flavanone skeleton, the major site of oxidation was at 3'position on the B ring. Other metabolites included oxidation at carbon-3 as well as desaturation of the C ring to produce 8-prenylapigenin. An unusual hydroxy quinone product formed by ipso hydroxylation of the B ring of 8-prenylnaringenin was also detected. This product was probably an intermediate for the B ring cleavage product, 8-prenylchromone.

Antimalarial activity of lavandulyl flavanones isolated from the roots of Sophora flavescens.

Four lavandulyl flavanones, (2S)-2'-methoxykurarinone (1), sophoraflavanone G (2), leachianone A (3), and (-)-kurarinone (4), which are isolated from the roots of Sophora flavescens have been tested for in vitro antimalarial activity against Plasmodium falciparum. Compounds 1-3 showed moderate antimalarial activities with EC(50) values of 2.4 x 10(-6), 2.6 x 10(-6), and 2.1 x 10(-6) M, respectively. These compounds did not show selective toxicity against P. falciparum in the toxicity test on mouse mammalian tumor cells, however, it is suggested that the position of methoxyl groups in flavanone skeleton plays an important role on antimalarial activity.

Antibacterial and antiandrogen flavonoids from Sophora flavescens.

Sixteen flavanones, three flavanonols, and four pterocarpans were isolated from the MeOH extract of the roots of Sophora flavescens. Twelve of these were new compounds, including eight prenylflavanones (1-8), one prenylflavanonol (9) and three novel pterocarpane derivatives (10-12). Their structures were elucidated using NMR and mass spectral methods. Some of these compounds have irregular C10 prenyl moieties at C-8 of the flavanone skeleton. These compounds exhibited significant antibacterial activities against the Gram-positive bacteria Staphylococcus aureus, Bacillus subtilis, S. epidermidis, and Propionibacterium acnes. They also exhibited antiandrogen activities.

Six flavonostilbenes and a flavanone in roots of Sophora alopecuroides

Six novel flavonostilbenes, alopecurones A-F, were isolated from the roots of Sophora alopecuroides, in addition to a new 5-deoxyflavanone with a lavandulyl group, alopecurone G. The structures of alopecurones A-F, which are flavonostilbenes composed of a flavanone [5,7,2′,4′-tetrahydroxy-8-lavandulylfavanone (sophoraflavanone G) or its 2′-methyl ether (leachianone A)] condensed with a stilbene [3,5,4′-trihydroxystilbene (resveratrol)] through the A ring of the flavanone skeleton, were established by spectroscopic analysis. Chemical relationships between S. alopecuroides, S. leachiana and S. moorcroftiana are discussed on the basis of their phenolic components.